Quebecaspis conifrons Fauna

The majority of the species described in this paper are new or placed in open nomenclature. However, Quebecaspis conifrons Rasetti, Reference Rasetti1961 is an important exception from CH 57 and HC 202 that is also present in Maryland (Rasetti, Reference Rasetti1961) and Alaska (Palmer, Reference Palmer1968). This species was originally described from the Rocky Springs Station Member of the Frederick Limestone near Frederick, Maryland (Brezinski et al., Reference Brezinski, Taylor and Repetski2012, p. 408), using collections from loose blocks in stone fences and in situ material from a nearby quarry (Rasetti, Reference Rasetti1961, p. 107). It is associated with Pterocephalops acrophthalma Rasetti, Reference Rasetti1944, which also occurs in HC 202, in addition to genera that are well represented in CH 57, HC 166, and HC 202, including Dunderbergia Walcott, Reference Walcott1924, Bathyholcus Rasetti, Reference Rasetti1961, Glyptometopsis Rasetti, Reference Rasetti1961, and the agnostids Acmarhachis kindlei Westrop and Eoff, Reference Westrop and Eoff2012 and A. whittingtoni Westrop and Eoff, Reference Westrop and Eoff2012 (sclerites that were assigned to A. acutus Kobayashi, Reference Kobayashi1938 by Rasetti, Reference Rasetti1961; see Westrop and Eoff, Reference Westrop and Eoff2012, p. 227–231, fig. 13.7–13.19 for discussion and reillustration of Rasetti’s specimens).

A similar assemblage, which shares Bathyholcus gaspensis Rasetti, Reference Rasetti1961 and P. acrophthalma with the Frederick Limestone fauna, is present in boulder 51 from a debris-flow conglomerate in the Lévis Formation at Lévis, Quebec (Rasetti, Reference Rasetti1944, Reference Rasetti1961, p. 108). It also includes species of Dunderbergia, Quebecaspis, and Onchopeltis.

Close comparisons can also be made with the trilobite assemblage from the Gorge Formation of Vermont described by Clark and Shaw (Reference Clark and Shaw1968) from the lower part of bed 3 in their stratigraphic section (Shaw and Clark, Reference Shaw and Clark1968), which they described (Clark and Shaw, Reference Clark and Shaw1968, p. 382) as an argillaceous or silty black limestone. Landing (Reference Landing1983) remeasured and redescribed the succession at Highgate Gorge and concluded that it recorded deposition in a continental slope setting, judging from sedimentary features such as debris flow conglomerates and thin-bedded, plane-laminated to micro-crossbedded limestone units that may be turbidites. Glyptometopsis parilimba n. sp. (recorded from Gorge bed 3 as G. tumida Rasetti, Reference Rasetti1961 by Clark and Shaw, Reference Clark and Shaw1968) is present in HC 202 and co-occurs with Q. conifrons in CH 57. The roster of other genera preserved in boulders HC 202, HC 166, and CH 57 and in the lower bed 3 of the Gorge Formation includes “Eugonocare” Whitehouse, Reference Whitehouse1939, Bellaspidella Rasetti, Reference Rasetti1945, Dunderbergia, and Pterocephalops.

There is ample evidence for a distinctive Steptoean (late Paibian) trilobite assemblage along the Cambrian margin of the Appalachian region from the Pennsylvania Reentrant to the St. Lawrence Promontory (Thomas, Reference Thomas1977; Lavoie et al., Reference Lavoie, Burden and Lebel2003, fig. 1). It includes a variety of genera such as Bathyholcus, Glyptometopsis, Pterocephalops, and Quebecaspis that are not only absent from shelf successions (Palmer, Reference Palmer1954, Reference Palmer1960, Reference Palmer1965) but also missing from deep shelf facies on the opposite side of Laurentia (Pratt, Reference Pratt1992). Although the number of shared species is relatively small, assemblages from Newfoundland, Quebec, Vermont, and Maryland almost certainly overlap in age, and we assign them to a new biostratigraphical unit, the Quebecaspis conifrons Fauna.

Sedimentological and stratigraphical information indicates that the Q. conifrons Fauna occupied similar environments in each region. As in Newfoundland, conglomerates of the Frederick Limestone contain numerous boulders of calcified algal boundstone (Demicco, Reference Demicco1985), and reconstruction of the shelf margin (Demicco, Reference Demicco1985, fig. 16) envisaged a rimmed shelf with buildups of calcified algae, as in Newfoundland (James, Reference James1981). Trilobite faunas from boulders in conglomerates like those from Newfoundland and Quebec are sourced from the shelf margin. However, Rasetti’s collections from the Frederick Limestone are in thin-bedded carbonates that form a distinct subfacies, with sedimentary structures such as ripple cross-lamination and grading (Demicco, Reference Demicco1985). These lithologies are comparable to the thin-bedded limestone facies of the Gorge Formation (Landing, Reference Landing1983), and this raises the possibility that the trilobites in bedded slope limestone are also allochthonous and derived from the shelf margin via turbidity currents. Indeed, Taylor (Reference Taylor1976; Taylor and Cook, Reference Taylor and Cook1976) argued from taphonomic criteria that some packstone beds with disarticulated trilobites in slope facies of the Sunwaptan (Jiangshanian) Hales Limestone of Nevada were sourced from shallower water, whereas horizons of articulated trilobites represent slope faunas preserved in situ.

Quebecaspis conifrons occurs in the Jones Ridge Limestone in the Hi-Yu area, east-central Alaska (Palmer, Reference Palmer1968). However, aside from Tholifrons Palmer, Reference Palmer1968, the associated fauna (Palmer, Reference Palmer1968, p. 11, 12), which includes Cernuolimbus Palmer, Reference Palmer1960, Elburgia Palmer, Reference Palmer1960, Iddingsia Walcott, Reference Walcott1924, Pterocephalia Roemer, Reference Roemer1849, and Sigmocheilus Palmer, Reference Palmer1960, is entirely different from those of the Appalachian margin. Although Q. conifrons is a significant biostratigraphical tie point, we do not assign the Alaskan assemblage to the Q. conifrons Fauna.

Although the Q. conifrons Fauna is a distinctive shelf-edge grouping of species that can be tracked along the Laurentian margin, correlation into the interior of the shelf is more difficult and relies on an association with Dunderbergia as a tie point. However, while there are species of Dunderbergia present in all assemblages of the Q. conifrons Fauna, none is shared with those of the best-studied interior successions of Texas (Palmer, Reference Palmer1954), Nevada, Utah (Palmer, Reference Palmer1960, Reference Palmer1965), and Tennessee (Rasetti, Reference Rasetti1965). As discussed in “Remarks” (section for D. magnatubercula n. sp.), the most widely reported species, D. variagranula Palmer, Reference Palmer1954, is problematic and has been routinely misidentified. Moreover, it is not possible to simply equate the presence of Dunderbergia with the Dunderbergia Zone because the lowest occurrences of the genus in Nevada are in the older Dicanthopyge and Prehousia zones (Palmer, Reference Palmer1965). We can say with confidence that the Q. conifrons Fauna correlates into the upper half of the Paibian Stage (mid-Steptoean) and probably lies within the Dunderbergia Zone. The strongest support for a correlation into the Dunderbergia Zone comes from Alaska, where species of Elburgia, Iddingsia, Pterocephalia, Cernuolimbus, and Sigmacephalus are associated with Q. conifrons (Palmer, Reference Palmer1968). However, all of these species are endemic to Alaska, so resolution is low, and this is compounded by the fact that the Dunderbergia Zone in Nevada and Utah is a thick stratal interval. For example, at Orr Ridge in Utah, the zone is about 90 m thick (Westrop, unpublished), and exactly where within this interval the Q. conifrons Fauna would fall is uncertain.

In short, ecological and biogeographical differentiation of the North American shelf is, not surprisingly, an impediment to inter-regional biostratigraphical correlation. Although comparison of the Q. conifrons Fauna and the classic succession of the Dunderberg Formation and correlatives in Nevada and Utah (Palmer, Reference Palmer1965) underscores these difficulties, it is worth noting that there are few species-level tie points between the latter region and, for example, the succession in Tennessee (Rasetti, Reference Rasetti1965), which may reflect biogeographical effects of the Transcontinental Arch (Carlson, Reference Carlson1999). Even in the shelf interior, there are barriers to high-resolution biostratigraphical correlation, which is possible only within lithofacies and biofacies belts.

Type species

Crepicephalus (Loganellus) nitida Hall and Whitfield, Reference Hall and Whitfield1877 from the Dunderberg Formation, northern Schell Creek Range, White Pine County, Nevada (by original designation).

Dunderbergia bovicephala new species

Figures 2–4

Reference Westrop and Eoff2012 Dunderbergia cf. D. seducta Palmer; Westrop and Eoff, p. 202.

Reference Westrop and Engel2023 Dunderbergia sp. nov. Westrop and Engel, fig. 3a, 3b.

Holotype

A cranidium (GSC 143199, Fig. 2.1–2.3) from the Downes Point Member, Shallow Bay Formation, boulder CH 49, Cow Head Peninsula, Newfoundland.

Paratypes

Four cranidia (GSC 144537, Fig. 2.4, 2.5; GSC 144538, Fig. 2.6, 2.7; GSC 144540, Fig. 3.1–3.3; GSC 144543, Fig. 3.8), one librigena (GSC 144539, Fig. 2.8, 2.9), one hypostome (GSC 144544, Fig. 3.9, 3.10), and six pygidia (GSC 143200, Fig. 4.1, 4.2; GSC 144545, Fig. 4.3, 4.4; GSC 144546, Fig. 4.5; GSC 144547, Fig. 4.6, 4.7; GSC 144548, Fig. 4.8; GSC 144549, Fig. 4.9, 4.10) from boulder CH 49; two cranidia (GSC 144541, Fig. 3.4, 3.5; GSC 144542, Fig. 3.6, 3.7) from boulder HC 180, Hickey Cove, western Newfoundland.

Additional material

In addition to the figured specimens, four cranidia and two pygidia from boulder CH 49 were complete enough to provide measurements.

Diagnosis

Anterior cranidial margin evenly rounded, not coming to a point. Anterior border long, occupying 40% (34–51%; lower values in larger specimens) of frontal area length. Palpebral lobe equal to 31% (26–40%) of glabellar length, centered opposite L2. Width between palpebral lobes greater than 85% width of anterior border. Sculpture of fine granules with scattered tubercles. Pygidium with relatively short axis that occupies 79% (76–83%) of pygidial length and 37% (35–41%) of pygidial width at the first axial ring. Border furrow shallow; border defined largely by change in slope at base of pleural field.

Occurrence

Downes Point Member, Shallow Bay Formation, western Newfoundland, boulder CH 49, Cow Head Peninsula and boulder HC 180, Hickey Cove. “Innitagnostus” inexpectans Fauna (Westrop and Eoff, Reference Westrop and Eoff2012).

Description

Cranidium strongly arched in anterior and lateral views; anterior margin curves smoothly forward. Maximum cranidial width at posterior margin equal to 143% (134–157%) of maximum length; width between palpebral lobes 67% (61–74%) of width of posterior margin. Frontal area occupies 28% (26–30%) of total cranidial length; divided into downsloping preglabellar field and gently convex anterior border; border accounts for 40% (34–51%) of frontal area. Anterior border furrow well defined; oblique abaxially, becoming weakly (Fig. 2.6) to strongly (Fig. 2.4) curved forward medially. Axial and preglabellar furrow narrow grooves. Glabella raised well above fixed cheeks; roughly trapezoidal but rounded anteriorly. Width at SO equal to 69% (65–75%) of glabellar length; narrows to 60% (56–68%) at anterior tip of S2. LO occupies 16% (13–20%) of glabellar length; carries low median node (Fig. 2.6). SO shallowest medially, deepening and curving forward abaxially, and bifurcating weakly on larger specimens. S1–S3 defined in part by absence of sculpture. S1 firmly impressed on external surface and internal mold; directed obliquely forward, bifurcating as it approaches axial furrow. S2 shallower, less steeply inclined than S1. S3 identifiable on external surface only as nearly transverse, smooth band of exoskeleton. Palpebral area of fixigena nearly flat. Palpebral ridge conspicuous, angled backward from just anterior S3 to palpebral lobes. Palpebral lobe on smaller specimens weakly upturned; most arcuate and centered opposite L2; length equal to 31% (26–40%) of glabellar length. Palpebral furrow gently impressed on external surface, deeper on internal mold. Anterior facial sutures straight or faintly sigmoid between palpebral lobes and anterior border, diverging so that frontal area widens anteriorly; course changes abruptly at anterior border furrow, following a forwardly curved path. Posterior sutures diverge backward along faintly sigmoid path. Postocular area of fixed cheeks flexed downward abaxially; posterolateral projection 32% (29–34%) total cranidial width, tapering to fine point. Posterior border furrow well defined, expanding abaxially. Posterior border length increases abaxially; length equal to 5% (3–7%) of glabellar length near axial furrow, increasing to 9% (7–11%) near sutural margin. Cranidial surface sculpture consists of small, closely spaced granules and scattered larger tubercles. Granulation absent in border furrows and S1–S3; tubercles lost on abaxial portion of SO and on palpebral lobe. Granules aligned along caecal markings on preglabellar and preocular fields. Tubercles expressed on internal mold; granules absent.

Librigena gently inflated; genal spine incomplete, preserved part less than 30% total length of librigenal field but likely much longer. Width at posterior of palpebral suture equal to 30% total length. Border convex, width equal to 10% of total librigenal length; doublure narrow, inner edge terminates beneath shallow lateral border furrow. Librigenal field with caecal network and granules but lacks tubercles. Internal mold of border and genal spine smooth and lacks tubercles.

Hypostome with elongate, convex middle body, width equal to slightly more than half of length. Posterior lobe very short, equal to about 10% of middle body length (sag.). Macula weak, roughly oval in outline; middle furrow not expressed between maculae. Anterior border short (sag.); expands into triangular anterior wing. Lateral border furrow firmly impressed, slightly wider (tr.) than convex, rim-like lateral border. Posterior border about half of width of lateral border; posterior border furrow very narrow (sag.) groove. Surface of hypostome poorly preserved; internal mold apparently smooth; limited areas of preserved exoskeleton with fine granules.

Pygidium roughly semielliptical with posterior margin becoming nearly straight medially; gently arched in posterior view (Fig. 4.10); length 61% (60–63%) width. Maximum axis width 37% (35–41%) of pygidial width; axis length 79% (76– 83%) of pygidial length. Axis comprises articulating half-ring, two transverse axial rings, and rounded terminal piece of at least two segments. Each ring separated by wide, prominent ring furrows that lack granules abaxially; shallower, incomplete furrow may be expressed on terminal piece (Fig. 4.1, 4.4). At least two pairs of distinct, broad pleural furrows separate narrow anterior and posterior pleural bands; interpleural furrows faint but visible on some specimens; beyond level of second axial ring, pleural field weakly furrowed. Border furrow shallow. Border almost flat (Fig. 4.2, 4.3, 4.6, 4.10), defined in part by change in slope at base of pleural field; maintains nearly even width before merging with low, indistinct post-axial ridge. Granules present everywhere on external surface, except in parts of axial furrows. Paired tubercles on axial rings, along with first segment of terminal piece; one or two tubercles on posterior pleural band. Indistinct caecal markings on some pleural bands and in the region of post-axial ridge.

Etymology

From bovis (Latin), “cow,” and kephalos (Greek), “head,” in reference to the occurrence of the species at Cow Head, Newfoundland.

Remarks

The combination of closely spaced, fine granules and scattered large tubercles on the cranidium of D. bovicephala n. sp. resembles the sculpture of D. seducta Palmer, Reference Palmer1968 (p. 62, pl. 7, figs. 21, 26–28) from the Jones Ridge Limestone, Jones Ridge region, east-central Alaska. Both species also have a relatively long anterior border. However, D. seducta differs in having palpebral areas of the fixed cheeks that are upsloping, rather than flat, a shorter frontal area, and palpebral lobes that are farther forward on the cranidium so that the palpebral ridges are more transversely oriented (Palmer, Reference Palmer1968, pl. 7, fig. 26). The pygidium of D. seducta (Palmer, Reference Palmer1968, pl. 7, fig. 21) resembles that of D. bovicephala (Fig. 4.1–4.10) but has a proportionately longer and wider axis, which results in a narrower (tr.) pleural field.

Among species from the Dunderberg Shale and correlatives in Nevada and Utah, D. nitida (Hall and Whitfield, Reference Hall and Whitfield1877) (Palmer, Reference Palmer1960, pl. 4, figs. 14–21, 23, 24), D. polybothra Palmer, Reference Palmer1960 (pl. 5, figs. 1–4, 6, 7, 9, 14), D. bigranulosa Palmer, Reference Palmer1960 (pl. 5, figs. 10–13, 15–23), and cranidia attributed to D. variagranula Palmer, Reference Palmer1954 by Palmer (Reference Palmer1960, pl. 4, figs. 22, 25) all possess short, rim-like, medially pointed anterior borders that contrast with the longer, evenly rounded border of D. bovicephala. In addition, the cranidium of D. nitida has a smooth external surface (Palmer, Reference Palmer1965, p. 41), whereas D. polybothra is coarsely pitted (Palmer, Reference Palmer1960, pl. 5, fig. 14, 1965, p. 42). Dunderbergia bigranulosa has an unusually slender genal spine on the librigena (Palmer, Reference Palmer1960, pl. 5, figs. 15–17), lacks the larger tubercles that augment the granules on D. bovicephala, and has a broader axis on the pygidium and, consequently, a narrower pleural field (Palmer, Reference Palmer1965, pl. 4, fig. 11). Dunderbergia anyta (Hall and Whitfield, Reference Hall and Whitfield1877) differs from D. bovicephala in having a much smaller, more anteriorly positioned, flap-like palpebral lobe, much wider pygidium, and finely granulose sculpture (Palmer, Reference Palmer1965, pl. 4, figs. 8, 10, 14). Dunderbergia calculosa Palmer, Reference Palmer1965 (pl. 5, figs. 6–10) has a proportionately longer pygidial axis extending almost to the posterior margin, a cranidial sculpture of fine granules with very few coarse tubercles, and a narrower (tr.) palpebral area of the fixigena so that the palpebral lobe is closer to the glabella.

Dunderbergia simplex Rasetti, Reference Rasetti1961 (pl. 24, figs. 1–6) and Dunderbergia cf. D. variagranula of Rasetti, Reference Rasetti1961 (pl. 24, figs. 7–9), both from loose blocks of Frederick Limestone in the Frederick Valley of Maryland, possess nearly transverse anterior border furrows that are distinct from the more arcuate border furrow of D. bovicephala. In addition, D. simplex has an external sculpture of “fine, indistinct granules” (Rasetti, Reference Rasetti1961, p. 112), whereas Dunderbergia cf. D. variagranula has numerous closely spaced tubercles (Rasetti, Reference Rasetti1961, pl. 24, fig. 7). Both species also differ in the morphology of the palpebral lobe. In D. simplex, the lobe is a much larger flap (Rasetti, Reference Rasetti1961, pl. 24, fig. 2) than in D. bovicephala (Fig. 2.1), but it is a very narrow (tr.) band in Dunderbergia cf. D. varigranula (Rasetti, Reference Rasetti1961, pl. 24, fig. 7).

Rasetti (Reference Rasetti1965) described two new species of Dunderbergia from the Nolichucky Formation of Tennessee. Of these, D. tennesseensis has a relatively long border, as in D. bovicephala, but has a more posteriorly positioned palpebral lobe that extends back to the midpoint of L1 (Rasetti, Reference Rasetti1965, pl. 15, fig. 1) and, consequently, a more oblique palpebral ridge. The pygidium is proportionately shorter and wider, with a nearly transverse posterior margin (Rasetti, Reference Rasetti1965, pl. 15, fig. 9). Dunderbergia longifrons Rasetti, Reference Rasetti1965 (pl. 15, figs. 13–18) has a much shorter frontal area than D. bovicephala.

Dunderbergia magnatubercula new species

Figures 5, 6

Figure 5.

Cranidia of Dunderbergia magnatubercula n. sp., Downes Point Member, Shallow Bay Formation, boulder MP 528, Martin Point, western Newfoundland. All paratypes. (1–3) GSC 144550: (1) dorsal view; (2) anterior view; (3) lateral view. (4–7) GSC 144551: (4) lateral view; (5) dorsal view; (6) posterior view; (7) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 5. Long description

Seven photographs of two paratype cranidia of Dunderbergia magnatubercula. White scale bars represent 1mm. Both specimens exhibit the tuberculate surface texture of small, raised bumps over the glabella and fixed cheeks.

Photographs 1–3 show a dorsal, anterior and lateral views of a specimen with a GSC catalogue number 144550. The lateral (side) view (photograph 3) shows the overall convexity of the specimen, including the steeply sloping frontal area.

Photographs 4–7 show lateral, dorsal, posterior and anterior views, respectively, of a specimen with a GSC catalogue number 144551. All views show the convexity and tapered outline of the glabella. The posterior (rear) view emphasizes the downward curvature of back of the cranidium

*

Figure 6.

Dunderbergia magnatubercula n. sp., Downes Point Member, Shallow Bay Formation, boulder MP 528, Martin Point, western Newfoundland. (1–4, 7, 8) Cranidia. (5, 6) Pygidium. (1–3) GSC 144552, holotype: (1) dorsal view; (2) anterior view; (3) lateral view. (4) GSC 144553, paratype, dorsal view. (5, 6) GSC 144554, paratype: (5) dorsal view; (6) posterior view. (7, 8) GSC 144555, paratype: (7) dorsal view; (8) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 6. Long description

Eight photographs of specimens of the trilobite Dunderbergia magnatubercula. Scale bars represent 1 mm.

Photographs 1–3 show dorsal, anterior and lateral views, respectively, of the holotype cranidium with the GSC catalogue number 144552. All photographs show the glabella and the tuberculation of the external surface of the shell. The lateral view (photograph 3) emphasizes the convex profile of the specimen.

Photograph 4 shows a dorsal view of a paratype cranidium with the GSC catalogue number 144553. This specimen preserves the external surface of the shell and shows the larger tubercles scattered among much finer granules.

Photographs 5 and 6 show dorsal and posterior views of a paratype pygidium with the GSC catalogue number 144554. Photograph five shows the segmentation of the central axis whereas photograph 6 shows the convexity of the axis.

Photographs 7 and 8 show a paratype cranidium with the GSC catalogue number 144555. They show the curvature of the anterior border (7) and the overall convexity of the cranidium (8).

Holotype

A cranidium (GSC 144552, Fig. 6.1–6.3) from the Downes Point Member, Shallow Bay Formation, boulder MP 528, Martin Point, western Newfoundland.

Paratypes

Four cranidia (GSC 144550, Fig. 5.1–5.3; GSC 144551, Fig. 5.4–5.7; GSC 144553, Fig. 6.4; GSC 144555, Fig. 6.7, 6.8) and a pygidium (GSC 144554, Fig. 6.5, 6.6) from the Downes Point Member, Shallow Bay Formation, boulder MP 528, Martin Point, western Newfoundland.

Diagnosis

Broad (tr.) cranidium, length equal to 90% (89–90%) of width across palpebral lobes. Distinctly sigmoid posterior branch of facial suture; slender (exsag.) posterolateral projection. Anterior border convex, accounts for 31% (28–34%) of frontal area length. External surface of cranidium with very fine granules and much larger, more widely spaced tubercles; granules not expressed on internal mold, which includes fine punctae. Pygidium with scattered fine tubercles on pleural field and paired tubercles on axial rings; granules present only on border and, faintly, on crest of axis. Concave border narrows posteriorly; separated from pleural field by weak paradoublural ridge.

Occurrence

Downes Point Member, Shallow Bay Formation, western Newfoundland, boulder MP 528, Martin Point.

Description

Cranidium convex, outline (excluding posterolateral projection) roughly rectangular; length equal to 90% (89–90%) of width across palpebral lobes; width expands at posterolateral projection to 147% (144–151%) of width across palpebral lobes. Frontal area gently inflated in lateral view; slopes steeply forward to weakly inflated anterior border (Fig. 5.3); occupies 29% (27–31%) of cranidial length in dorsal view. Anterior border flexed forward, accounts for 31% (28–34%) of frontal area length (sag.) in dorsal view. Anterior border narrow, firmly impressed groove; has distinct forward curve in front of glabella. Axial and preglabellar furrows finely etched grooves on external surface (Fig. 6.4), deeper on internal mold (Fig. 5.1). Glabella convex, occupies 71% (70–73%) of cranidial length, with width at SO equal to 74% (66–80%) glabellar length; tapers forward, well rounded (Fig. 5.5) to more truncate (Fig. 6.7) anteriorly. LO comprises 13% of glabellar length (sag.); posterior margin curved gently backward. SO deeply incised on external surface and internal mold over most of width (tr.), length (sag.) roughly equal to LO; deflected forward abaxially, narrowing (exsag.) abaxially into finely etched groove (Fig. 6.4). Lateral glabellar furrows weakly impressed on external surface, defined in part by absence of sculpture (Fig. 6.4); better expressed on internal mold (Fig. 5.1). S1 bigeniculate, bifurcating adaxially on some specimens (Fig. 5.1). S2 weakly (Fig. 5.5) to strongly (Fig. 5.1) geniculate, with abaxial segment nearly transverse. S3 barely perceptible on internal mold, nearly transverse, terminates short of glabellar margin. Palpebral area of fixigena broad, equal to 58% (57–59%) of glabellar width at SO, slopes upward from axial furrow. Palpebral lobe forms arcuate flap, length (exsag.) equal to 34% (28–38%) glabellar length; centered just in front of abaxial tip of S1. Palpebral furrow firmly impressed on external surface and internal mold. Palpebral ridge well defined, gently curved, extends forward from palpebral lobe to reach axial furrow near S3. Anterior branches of facial sutures diverge slightly along nearly straight paths between palpebral lobes and anterior border before swinging abruptly inward along anterior cranidial margin; posterior branches sigmoid, nearly parallel immediately behind palpebral lobe before diverging along increasingly curved path. Posterolateral projection short (exsag.) but wide (tr.), accounting for 32% (27–35%) of total cranidial width across posterior margin. Posterior border furrow well incised; posterior border convex, lengthens slightly (exsag.) toward sutural margin. Sculpture includes closely spaced fine granules over entire surface except furrows. More widely spaced tubercles spread over glabella, fixigenae, anterior and posterior borders, and palpebral lobe. Cephalic median organ present on LO (Fig. 6.4). Surface of internal mold punctate rather than granulose; tubercles expressed on mold but noticeably smaller than on external surface (compare Figs. 5.1 and 6.1).

Pygidium nearly semicircular in outline, length (sag.) slightly more than 55% of maximum width. Axis long, strongly convex, gently tapered; occupies about 85% of pygidial length (sag.) and 35% of maximum pygidial width. Transverse articulating half-ring with firmly impressed articulating furrow; axial ring furrows also firmly impressed, separate two transverse axial rings; terminal piece with incomplete transverse furrow at anterior. Postaxial ridge present. Pleural field nearly flat at axial furrow, flexed down distally (Fig. 6.6). Concave border narrows posteriorly; separated from pleural field by weak paradoublural ridge. At least three pairs of distinct pleural furrows separating pleural bands of roughly equal length (exsag.); interpleural furrows not expressed. Sculpture of scattered fine tubercles on pleural ribs; paired tubercles on axial rings and anterior segment of terminal piece; granules present only on border and, faintly, on crest of axis.

Etymology

From magnus (Latin), “large,” and tuberculum (Greek), “bump or protuberance,” in reference to the conspicuous tubercles on the cranidium.

Remarks

The tuberculate sculpture of the cranidium resembles the surface of D. variagranula Palmer, Reference Palmer1954 from the Riley Formation of central Texas. The specimens illustrated by Palmer include a cranidium with sculpture of fine tubercles (holotype; Palmer, Reference Palmer1954, pl. 88, fig. 7) and one with a more pitted surface (paratype; Palmer, Reference Palmer1954, pl. 88, fig. 9). He considered the two cranidia to record the extremes of variation (figure caption for pl. 88). Palmer (Reference Palmer1960) later decided that these specimens actually represented two distinct species, and the only sclerite from the type area in Texas that we can be sure belongs to D. variagranula is the holotype. Unfortunately, this specimen is incomplete, lacking palpebral lobes, among other features, and this limits comparisons with other species. As such, D. variagranula might be better viewed as a nomen dubium. Dunderbergia magnatubercula differs in the course of the posterior branch of the facial suture, which is distinctly sigmoid with strongest curvature at the anterior end, and this produces a slender (exsag.) posterolateral projection (Fig. 6.7). The holotype of D. variagranula retains exoskeleton on the right fixigena, and this shows that the tubercles are much smaller than in D. magnatubercula (Fig. 6.1).

Palmer (Reference Palmer1960, Reference Palmer1965) also assigned specimens from Nevada to D. variagranula, although this cannot be verified with any certainty from the published record. Two cranidia from the Dunderberg Formation in the Eureka District (Palmer, Reference Palmer1960, pl. 4, figs. 22, 25) have an angular anterior border, a truncate glabella, and widely spaced fine tubercles. They differ from D. magnatubercula most clearly in having a narrower (tr.) palpebral area of the fixigenae so that the palpebral lobe is closer to the glabella. The pygidium (Palmer, Reference Palmer1965, pl. 5, fig. 3) has a well-defined border in the form of a convex rim. By contrast, the pygidium of D. magnatubercula (Fig. 6.5, 6.6) has a concave border that is separated from the pleural field by a faint paradoublural ridge rather than a border furrow. A third cranidium (Palmer, Reference Palmer1965, pl. 5, fig. 4) attributed to D. variagranula is from the Nopah Formation, near Devil’s Hole, Ash Meadows National Wildlife Refuge, southern Nevada, about 350 km south of Eureka. It arguably represents a distinct species from the specimens from Eureka as it has a curved anterior border, well-rounded glabella, and more closely spaced tubercles.

The species that Rasetti (Reference Rasetti1961) identified as D. variagranula (from Quebec; Rasetti, Reference Rasetti1961, pl. 24, fig. 10) and Dunderbergia cf. D. variagranula (from Maryland; Rasetti, Reference Rasetti1961 pl. 24, fig. 7) were each illustrated with a single cranidium. The tubercule size and distribution of the specimen from Maryland is similar to the sculpture of Palmer’s (Reference Palmer1960, pl. 4, figs. 22, 25) cranidia from Eureka, which differ in having a much larger palpebral lobe. Dunderbergia magnatubercula also differs in this respect, and it has an anterior border furrow that is deflected forward (Fig. 5.1), rather than nearly transverse, as in Dunderbergia cf. D. variagranula, and a wider (tr.) palpebral area of the fixigena. The specimen from Quebec is incomplete posteriorly and is difficult to compare with material from other regions. It has finer tuberculate sculpture than D. magnatubercula and has a more transverse anterior border furrow without a medial deflection.

Cranidia of D. punctata (Rusconi, Reference Rusconi1958), from allochthonous blocks of La Cruz olistoliths of Mendoza, Argentina, resemble D. magnatubercula in the distribution of tubercles and in the angular anterior border (Tortello, Reference Tortello2025, fig. 1c–o). Dunderbergia punctata differs in having a narrower (tr.) palpebral area of the fixigena, a more posteriorly positioned palpebral lobe, and consequently, a more strongly oblique palpebral ridge (Tortello, Reference Tortello2025, fig. 1j).

Dunderbergia bovicephala (Figs. 2–4), the most abundant member of the genus in the Shallow Bay Formation, has a much lower density of tubercles on the cranidium than D. magnatubercula, particularly on the fixigenae, and has a longer, relatively flat anterior border. The pygidium of D. bovicephala has a border furrow, and the border maintains a nearly even width, whereas the border of D. magnatubercula narrows posteriorly and is separated from the pleural field by a weak paradoublural ridge rather than a furrow. Dunderbergia astropletha n. sp. (Fig. 7), also from the Shallow Bay Formation, has cranidial and pygidial sculpture consisting exclusively of fine, closely spaced granules. The pygidium has a shallow border furrow and a narrow, nearly flat border that maintains an even width.

Figure 7.

Dunderbergia astropletha n. sp., Downes Point Member, Shallow Bay Formation, boulder CH 54, Cow Head Peninsula, western Newfoundland. (1–4, 9, 10) Cranidia. (5–8, 11–13) Pygidia. (1–3) GSC 144556, holotype: (1) anterior view; (2) lateral view; (3) dorsal view. (4) GSC 144557, paratype, dorsal view. (5, 6) GSC 144558, paratype: (5) posterior view; (6) dorsal view. (7, 8) GSC 144559, paratype: (7) posterior view; (8) dorsal view. (9) GSC 144560, paratype, dorsal view. (10) GSC 144561, paratype, dorsal view. (11, 12) GSC 144562, paratype: (11) posterior view; (12) dorsal view. (13) GSC 144563, paratype, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 7. Long description

The figure contains 13 photographs of specimens of Dunderbergia astropletha. White scale bars represent 1 mm.

* Photographs 1–3 show anterior, lateral and dorsal views, respectively, of the holotype cephalon with the GSC catalogue number 144556. Photographs 1 and 2 show the convexity of the cranidium in front and side views, whereas photograph 3 shows the uniformly small granules on the external surface of the shell that characterize this species.

Photograph 4 shows a dorsal view of a paratype cranidium with the GSC catalogue number 144557. The specimen preserved the palpebral lobe on the right side.

Photographs 5 and 6 show posterior and dorsal views of a paratype pygidium with the GSC catalogue number 144558. The dorsal view (6) preserved three incomplete thoracic segments.

Photographs 7 and 8 show posterior and dorsal views of a paratype pygidium with the GSC catalogue number 144559. The posterior view (7) shows the convexity of the axis, whereas the dorsal view shows the outlines of the axis and the pygidium, as well as the fine granules on the surface.

* Photographs 9 and 10 show dorsal views of paratype cranidia with GSC catalogue numbers 144560 and 144561, respectively. Both cranidia are incompletely preserved but show the tapered glabella.

Photographs 11 and 12 show posterior and dorsal views of a paratype pygidium with the GSC catalogue number 144562. Both views show the fine granules of the surface.

Photograph 13 shows a dorsal view of a paratype pygidium with the GSC catalogue number 144563 It is smaller than the other pygidia, although the axis is broken.

Dunderbergia astropletha new species

Figure 7

Holotype

A cranidium (GSC 144556, Fig. 7.1–7.3) from the Downes Point Member, Shallow Bay Formation, boulder CH 54, Cow Head Peninsula, western Newfoundland.

Paratypes

Three cranidia (GSC 144557, Fig. 7.4; GSC 144560, Fig. 7.9; GSC 144561, Fig. 7.10) and four pygidia (GSC 144558, Fig. 7.5, 7.6; GSC 144559, Fig. 7.7, 7.8; GSC 144562, Fig. 7.11, 7.12; GSC 144563, Fig. 7.13) from the Downes Point Member, Shallow Bay Formation, boulder CH 54, Cow Head Peninsula, western Newfoundland.

Diagnosis

Sculpture of densely packed, fine granules over entire cranidial and pygidial surfaces except for smooth lateral glabellar furrows; arrayed along caecal network on preglabellar field; augmented by terrace ridges along anterior edge of anterior border (Fig. 7.1–7.3). Frontal area short (sag.), equal to 24% (24–25%) of cranidial length. Narrow (sag.), gently curved anterior border of even width; occupies 35% (31–37%) of frontal area length; border furrow evenly curved. Pygidium broad (tr.), length equal to 53% (50–56%) pygidial width. Border narrow (sag., exsag.), maintaining even width along lateral and posterior pygidial margins.

Occurrence

Downes Point Member, Shallow Bay Formation, western Newfoundland, boulder CH 54, Cow Head Peninsula. “Innitagnostus” inexpectans Fauna (Westrop and Eoff, Reference Westrop and Eoff2012).

Description

Cranidium convex; roughly quadrate outline interrupted posteriorly by broad (tr.) posterolateral projection; gently curved anterior margin; width across palpebral lobes about 95% of cranidial length; width at palpebral lobes is 68% (64–69%) of maximum width at posterior margin. Frontal area occupies 24% (24–25%) of cranidial length. Narrow (sag.), gently curved anterior border of even width; accounts for 35% (31–37%) of frontal area length. Border furrow evenly curved. Preglabellar field weakly inflated. Axial furrows distinct, preglabellar furrow less so, shallowing medially to produce slit-like pits abaxially (Fig. 7.9). Glabellar outline nearly trapezoidal, rounded anteriorly; occupies 76% (75–79%) of cranidial length; width at SO equal to 72% (64–74%) of length, decreasing to 63% (58–69%) at S2. SO deep and narrow (sag., exsag.), curved gently backward; may bifurcate on some specimens (Fig. 7.9). LO with curved posterior margin; accounts for 17% (14–18%) of glabellar length. Lateral glabellar furrows marked by lack of granulation on external surface. S1 well incised, particularly on internal mold, curving backward from glabellar margin. S2 nearly parallel to S1, incised on internal mold but identifiable only absence of sculpture on surface of exoskeleton. Gently curved S3 barely incised on internal mold (Fig. 7.10) but expressed only as smooth band of exoskeleton on external surface (Fig. 7.3). Palpebral area of fixigenae nearly flat; width equal to 18% (17–19%) of cranidial length. Palpebral lobe arcuate, length equal to 32% (29–35%) glabellar length, centered near anterior tip of S1. Palpebral ridge well defined on external surface of exoskeleton and internal mold, extends forward from palpebral lobe, reaching axial furrow opposite S3. Anterior branches of facial sutures diverge along nearly straight paths between palpebral lobes and anterior border furrow; converge abruptly inward along anterior cranidial margin; posterior branches diverge along sigmoidal paths. Sculpture of densely packed, fine granules over entire cranidial surface except for smooth lateral glabellar furrows; arrayed along caecal network on preglabellar field; augmented by terrace ridges along anterior edge of anterior border.

Pygidium semielliptical in outline, length equal to 53% (50–56%) of width, with narrow (tr.) articulating facets at anterior corners; gentle median arch of posterior margin (Fig. 7.5). Axis strongly convex, gently tapered, occupies 87% (84–90%) of pygidial length and 38% (34–40%) of maximum pygidial width; weak postaxial ridge expressed on some specimens (Fig. 7.12). Articulating half-ring semielliptical in outline; articulating furrow nearly transverse, firmly impressed. Axial ring furrows also nearly transverse and well incised. Two subequal, transverse axial rings occupy 42% (38–44%) length. Terminal piece with weak, incomplete transverse furrow expressed on some specimens (Fig. 7.12). Pleural field weakly arched, carries at least three pairs of broad (exsag.), shallow pleural furrows separating shorter (exsag.) pleural bands; posterior pleural bands with faint caecal markings (Fig. 7.6, 7.12). Border narrow (sag., exsag.), maintaining even width; identifiable in part by reduced size of granules. Border furrow shallow. Closely spaced granules present over entire external surface of exoskeleton, including furrows; internal mold faintly punctate.

Etymology

From astropletha (Greek), “full of stars,” in reference to the granules, which on certain sections of cranidial internal molds are packed together, recalling the “connect-the-dots” patterns used to depict constellations.

Remarks

Dunderbergia astropletha differs from the other species from the Shallow Bay Formation, D. bovicephala and D. magnatubercula, in having sculpture consisting solely of fine granules. In addition, the anterior border of D. bovicephala is about twice the length of the border of D. astropletha, and the frontal area as a whole is also relatively longer. The pygidium of the former is separated from the latter by its wider border (compare Figs. 4.1, 4.5 with Figs. 7.6, 7.12, 7.13). The proportions of the frontal area of D. magnatubercula are closer to those of D. astropletha, but the anterior border is distinctly angular and narrows abaxially; the border furrow is curved forward medially. In addition, the pygidium of D. magnatubercula (Fig. 6.5, 6.6) appears to have been relatively narrower and has a poorly defined border.

In terms of pygidial width, D. astropletha approaches D. anyta (Palmer, Reference Palmer1965, pl. 4, fig. 10) but differs in having a relatively wider axis. Cranidia of D. anyta are readily differentiated by their much smaller, more anteriorly positioned palpebral lobe, narrower (tr.) palpebral area of the fixigena, and longer frontal area (Palmer, Reference Palmer1965, pl. 4, fig. 8).

Both D. nitida and D. simplex can be differentiated from D. astropletha on the basis of their sculpture: D. nitida has a mostly smooth external surface (Palmer, Reference Palmer1965, p. 41) whereas D. simplex has very fine granules, although they cannot be discerned in Rasetti’s (Reference Rasetti1961, pl. 35, figs. 1–5) photographs. Dunderbergia calculosa also has a surface that is so finely granulose that it is not evident in published photographs (Palmer, Reference Palmer1965, pl. 5, fig. 8). It differs from D. astopletha in having a distinctly arcuate anterior border and palpebral lobes that are located closer to the glabella. The pygidium (Palmer, Reference Palmer1965, pl. 5, fig. 10) is narrower (tr.) than that of D. astropletha. Dunderbergia polybothra Palmer, Reference Palmer1960 is unusual in that the external surface is punctate rather than granulose (Palmer, Reference Palmer1965, p. 42).

The broad (tr.) pygidium of D. astropletha separates it from several species with narrower pygidia, including D. tennesseensis (Rasetti, Reference Rasetti1965, pl. 15, fig. 11), D. longifrons (Rasetti, Reference Rasetti1965, pl. 15, fig. 18), D. bigranulosa (Palmer, Reference Palmer1965, pl. 4, fig. 11), and material attributed to D. variagranula by Palmer (Reference Palmer1965, pl. 5, fig. 3).

Dunderbergia sp. indet.

Figure 8

Figure 8.

Cranidia of Dunderbergia sp. indet. from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove, western Newfoundland. (1) GSC 144639, dorsal view. (2) GSC 144640, dorsal view. (3–5) GSC 144641: (3) dorsal view; (4) lateral view; (5) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 8. Long description

Five photographs showing three cranidia of Dunderbergia sp. indet. White scale bars represent 1 mm

Photograph 1 shows a dorsal view of specimen with the GSC catalogue number 144639. The glabella.

Photograph 2 shows a dorsal view of a specimen with the GSC catalogue number 144640. This specimen is more complete on the right side, showing the fixed cheek and the posterior border furrow.

Photographs 3–5 shows dorsal, lateral and anterior views, respectively, of a specimen with the GSC catalogue number144641. in dorsal view. It is smaller than the other cranidia and preserves the palpebral lobe.

Material and occurrence

Three cranidia (GSC 144639, Fig. 8.1; GSC 144640, Fig. 8.2; GSC 144641, Fig. 8.3–8.5) from the Downes Point Member, Shallow Bay Formation, western Newfoundland, boulder HC 202, Hickey Cove area. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

Both the anterior border and border furrow of Dunderbergia sp. indet. are angular, rather than curved, although the amount of forward deflection medially is weak; the border narrows (exsag.) abaxially. In these features, it resembles two cranidia illustrated by Rasetti (Reference Rasetti1961). Of these, Dunderbergia cf. D. variagranula differs in having an unusually narrow (tr.) palpebral lobe and a sculpture of finer, more closely spaced tubercles (Rasetti, Reference Rasetti1961, pl. 24, figs. 7, 8). Tuberculate sculpture is also finer and densely packed in the incomplete cranidium identified as D. variagranula by Rasetti (Reference Rasetti1961, pl. 24, figs. 10–12). The palpebral lobes of this specimen are similar in size to those of Dunderbergia sp. indet., but it appears to have less-divergent anterior branches of the facial sutures, and consequently, the frontal area is relatively narrower (tr.).

Family Dokimocephalidae Kobayashi, Reference Kobayashi1935

Remarks

Westrop et al. (Reference Westrop, Waskiewicz Poole and Adrain2010) performed a phylogenetic analysis of what they termed Dokimocephalidae sensu stricto, which was a core group of genera that included Dokimocephalus Walcott, Reference Walcott1924, Iddingsia Walcott, Reference Walcott1924, Plataspella Wilson, Reference Wilson1949, Burnetiella Lochman, Reference Lochman1958, Edithiella Kurtz, Reference Kurtz1975, and Stittella Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010. The results indicated that each of these genera were monophyletic and that they were also part of a more inclusive clade. However, the status of other genera traditionally assigned to Dokimocephalidae, including Onchopeltis Rasetti, Reference Rasetti1944, Kindbladia Frederickson, Reference Frederickson1948, Deckera Frederickson, Reference Frederickson1949, Dellea Wilson, Reference Wilson1949, Pseudosaratogia Wilson, Reference Wilson1951, and Calocephalites Kurtz, Reference Kurtz1975, was left unresolved. A broader analysis will be part of future work, and in this paper, we will simply follow the traditional understanding of the family. We show that Glyptometopsis Rasetti, Reference Rasetti1961 is related to Kindbladia and include it in Dokimocephalidae.

Genus Onchopeltis Rasetti, Reference Rasetti1944

Type species

Onchopeltis spectabilis Rasetti, Reference Rasetti1944 from the Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec (by original designation).

Diagnosis

Cranidium strongly convex with anterior arch; glabella stands well above nearly flat palpebral area of fixigena. Anterior border long, accounting for about 60% of frontal area length. Palpebral lobe centered opposite L2. Pygidium roughly circular in outline, with narrow (tr.) pleural fields and broad (tr.), convex axis composed of two axial rings and terminal piece of at least two segments.

Remarks

Onchopeltis was established by Rasetti (Reference Rasetti1944) for sclerites from a single boulder from the Lévis Formation, Quebec City. Shergold and Webers (Reference Shergold and Webers1992) added species, albeit some questionably, from the Minaret Formation, Ellesworth Mountains, West Antarctica. They (Shergold and Webers, Reference Shergold and Webers1992, p. 139) argued that Onchopeltis intergraded with Protemnites Whitehouse, Reference Whitehouse1939 from Queensland, Australia, and entertained the possibility that the latter genus was a senior synonym of Olentella Ivshin, Reference Ivshin1956 from Kazakhstan. Paterson and Laurie (Reference Paterson and Laurie2004) also considered Onchopeltis, Protemnites, and Olentella to be close relatives. The various comments effectively cast doubt on monophyly of these genera.

The type species of Onchopeltis, O. spectabilis, has a prominent, strongly convex cranidium, with a glabella that stands well above the flat palpebral area of the fixigena (Fig. 9.1, 9.2; Rasetti, Reference Rasetti1944, pl. 39, figs. 1, 2), as does O. anconis n. sp. from the Shallow Bay Formation (Fig. 10.1–10.3, 10.6–10.9). Both species also have a long anterior border that occupies about 60% of frontal area length and a very short palpebral lobe centered opposite L2. The pygidium that Rasetti (Reference Rasetti1944, pl. 39, fig. 5) assigned to O. spectabilis is, like the cranidium and librigena, a relatively large sclerite. It is characterized by a roughly circular outline, wide (tr.) axis, and consequently, narrow pleural fields. Shergold and Webers (Reference Shergold and Webers1992, p. 137) questioned the pygidial association proposed by Rasetti (Reference Rasetti1944) and suggested a “nonillustrated paratype pygidium in the British Museum collection that is distinctly more elviniid” as an alternative. Unfortunately, this specimen remains unillustrated, but we see no reason to doubt Rasetti’s original assignment. Indeed, the large size of Rasetti’s pygidium (about 11 mm sag.) is consistent with the dimensions of the holotype cranidium of O. spectabilis (15 mm sag.) and so is an argument in favor of the association.

Figure 9.

Cranidia of trilobites from the Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec. (1, 2) Onchopeltis spectabilis Rasetti, Reference Rasetti1944. GSC 144567 (LU 1154a), holotype: (1) dorsal view; (2) anterior-oblique view. (3–5) Pterocephalops acrophthalma Rasetti, Reference Rasetti1944: (3) GSC 144568 (LU 1163a), designated as lectotype, dorsal view; (4, 5) GSC 144569 (LU 1163b), paralectotype: (4) dorsal view; (5) anterior-oblique view. (6) Quebecaspis breviceps Rasetti, Reference Rasetti1944, GSC 144570 (LU 1168a), designated as lectotype, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 9. Long description

Six photographs of trilobite species from Lévis, Quebec, that were described originally by Rasetti (1944). The white scale bars represent 1 mm.

Photoraphs 1 and 2 are dorsal and anterior-oblique views of the holotype cranidium of Onchopeltis spectabilis with the GSC catalogue number 144567. Both images show the strongly convex glabella that is characteristic of Onchopeltis.

Photograph 3 shows a dorsal view of the lectotype cranidium of Pterocephalops acrophthalma with the GSC catalogue number 144568. White arrows point to paired tubercles on the fixigena. The glabella and anterior border are also clearly visible.

Photographs 4 and 5 show dorsal and anterior-oblique views of the paralectotype cranidium of Pterocephalops acrophthalma with the GSC catalogue number 144569. The anterior-oblique view (5) shows the steeply sloping preglabellar field and the weakly concave anterior border.

Photograph 6 shows a dorsal view of the lectotype cranidium of Quebecaspis breviceps with the GSC catalogue number 144570. This specimen shows a very short preglabellar field and prominent glabella with a geniculate S1 furrow.

Figure 10.

Onchopeltis anconis n. sp., boulder HC 166, Downes Point Member, Hickey Cove, Shallow Bay Formation, western Newfoundland. (1–3) Cranidium, GSC 144564, holotype: (1) lateral view; (2) dorsal view; (3) anterior view. (4, 5) Librigena, GSC 144565, paratype: (4) lateral view; (5) dorsal view. (6–8) Cranidium, GSC 144566, paratype: (6) anterior view; (7) lateral view; (8) dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 10. Long description

Eight photographs of the type specimens of Onchopeltis anconis.

Photographs 1–3 show lateral, dorsal and anterior views, respectively, of the holotype cranidium with the GSC catalogue number 144564. The white scale bars represent 1 mm. All three figures show the extreme convexity of the specimen, including the large, tapered glabella, the short frontal area, and the small palpebral lobe.

Photographs 4 and 5 show dorsal and lateral views of the paratype librigena with the GSC catalogue number 144565. The photographs show the charcteristic genal spine that is directed outward (4) and upward (5)

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Photographs 6– 8 show anterior, lateral and dorsal views of a second paratype cranidium with the GSC catalogue number144566. The anterior view (6) shows the anterior arch of the cranidium whereas the lateral view shows the steeply sloping frontal area.

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Among the species described by Shergold and Webers (Reference Shergold and Webers1992) from the Minaret Formation of West Antarctica, O. variabilis is most like O. spectabilis and O. anconis, sharing the strong cranidial convexity with a distinct anterior arch, a small palpebral lobe, and tuberculate sculpture (Shergold and Webers, Reference Shergold and Webers1992, pl. 4, figs. 1–8). However, the anterior border is relatively shorter, and the glabella is less elevated above an inflated, rather than flat, palpebral area of the fixigena (compare Shergold and Webers, Reference Shergold and Webers1992, pl. 4, figs. 6, 7 with Fig. 10.1, 10.3). The associated pygidium (Shergold and Webers Reference Shergold and Webers1992, pl. 4, fig. 10) is relatively wide (tr.) and semielliptical in outline, and the long, relatively narrow axis has three distinct axial rings and a terminal piece composed of at least two segments. A complete understanding of relationships of the various species assigned to Onchopeltis will require a comprehensive phylogenetic analysis of Dokimocephalidae, and this will be dealt with elsewhere. For the present, O. variabilis is assigned only questionably to the genus, and a provisional generic diagnosis is based on characters shared between O. spectabilis and O. anconis.

Onchopeltis? acis Shergold and Webers, Reference Shergold and Webers1992 and O.? neutra Shergold and Webers, Reference Shergold and Webers1992 may be better assigned at least provisionally to Protemnites. The holotype cranidium of O.? neutra is well preserved and shows that the anterior border furrow is firmly impressed in front of the preocular field but shallows markedly in front of the glabella (Shergold and Webers, Reference Shergold and Webers1992, pl. 5, fig. 7). This is also the case in O.? acis (Shergold and Webers, Reference Shergold and Webers1992, pl. 5, fig. 6) and Protemnites? magnificans Shergold and Webers, Reference Shergold and Webers1992 (Shergold and Webers, Reference Shergold and Webers1992, pl. 6, figs. 2, 3) as well as P. burkensis Shergold, Reference Shergold1982 (Shergold, Reference Shergold1982, pl. 9, fig. 3). It is conceivable that the medial shallowing of the border furrow will prove to be a synapomorphy of Protemnites, and we transfer O.? acis and O.? neutra questionably to that genus.

Onchopeltis sp. from the Spurs Formation of Northern Victoria Land, Antarctica (Cooper et al., Reference Cooper, Jago and Begg1996, fig. 9A, B, E, G) appears to have an upsloping palpebral area of the fixigena, with a palpebral lobe that is located closer to the glabella and farther forward than in O. spectabilis and O. anconis. The glabella is distinctly tapered and nearly truncate anteriorly. We doubt that it is related to the Laurentian species.

Bigranulella Shaw and Clark, Reference Shaw and Clark1968 may also be related to Onchopeltis. Like O.? variabilis, the type species, B. latigenae Clark in Clark and Shaw, Reference Clark and Shaw1968, has inflated fixigenae (Clark and Shaw, Reference Clark and Shaw1968, pl. 55, figs. 27, 30, 33) that distinguish it from O. spectablis and O. anconis. The long anterior border, weakly arched in anterior view, is comparable to the border of O. spectabilis. The palpebral lobe of B. latigenae is incompletely preserved on all cranidia illustrated by Clark and Shaw (Reference Clark and Shaw1968) but appears to have been small. It is possible that Bigranuella will prove to be a synonym of Onchopeltis, but the type material of B. latagenae needs to be restudied before any decision can be made.

Kyphocephalus Miller, Reference Miller1936 resembles Onchopeltis. The type species, K. bridgerensis Miller, Reference Miller1936 from Wyoming, is poorly known and needs to be restudied. Miller’s (Reference Miller1936, pl. 8, figs. 30–33) photographs are small, but they show that the glabella is parallel-sided and weakly rounded anteriorly and lacks the extreme convexity of O. spectabilis and O. anconis. S1 and S2 lateral furrows are firmly impressed. The anterior border appears to dip almost vertically downward from the border furrow (Miller, Reference Miller1936, pl. 8, fig. 32), and the lateral border of the free cheek also seems to be steeply inclined (Miller, Reference Miller1936, pl. 8, fig. 30). Kyphocephalus ponderosus Wilson, Reference Wilson1951, from the Gatesburg Formation of Pennsylvania (Wilson, Reference Wilson1951, pl. 93, figs. 16–19), also has a steeply inclined anterior border, and this may be a synapomorphy for the genus. It is closer to Onchopeltis in glabellar convexity (Wilson, Reference Wilson1951, pl. 93, fig. 17) and, like K. bridgerensis, it has well-defined lateral glabellar furrows.

Onchopeltis spectabilis Rasetti, Reference Rasetti1944

Figure 9.1, 9.2

Reference Rasetti1944 Onchopeltis spectabilis Rasetti, p. 249, pl. 39, figs. 1–5.

Reference Rasetti1961 Onchopeltis spectabilis; Rasetti, p. 108.

Holotype

A cranidium (GSC 144567, Fig. 9.1–9.2) from boulder 51, Lévis Formation, Middle Ridge, Quebec City, Quebec.

Diagnosis

Librigena with long genal spine directed almost straight back, continuing the curvature of the rest of the lateral margin. Cranidium with parafrontal band in front of the glabella.

Occurrence

Lévis Formation, Boulder 51, Middle Ridge, Quebec City, Quebec; Quebecaspis conifrons Fauna.

Remarks

Although the holotype of O. spectabilis (Fig. 9.1, 9.2) resembles cranidia of O. anconis from HC 166 (Fig. 10.1–10.3, 10.6–10.8), there are clear differences in the librigenae. In O. spectabilis, the long genal spine is directed almost straight back and continues the curvature of the rest of the lateral margin (Rasetti, Reference Rasetti1944, pl. 39, fig. 3). By contrast, the librigena associated with cranidia of O. anconis (Fig. 11.4, 11.5) has the genal spine directed outward, with a sharp deflection of the lateral margin. In lateral view, the spine is also oriented upward. The cranidium of O. spectabilis has an inflated parafrontal band in front of the glabella, and this is not evident in O. anconis.

Figure 11.

Onchopeltis? sp. 1, Downes Point Member, Shallow Bay Formation, boulder HC 202, Cow Head Peninsula, western Newfoundland. All cranidia. (1–3) GSC 144571: (1) dorsal view; (2) anterior view; (3) lateral view. (4–6) GSC 144572: (4) lateral view; (5) dorsal view; (6) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 11. Long description

Six photographs of cranidia of Onchopeltis? sp. indet.

Photographs 1–3 show dorsal, anterior and lateral views, respectively, of a cranidium with the GSC catalogue number144571. White scale bars represent 1 mm. They demonstrate that the glabella is less convex than the glabella of Onchopeltis anconis (Fig. 10).

Photographs 4-6 show lateral, dorsal and anterior views of a cranidium with the GSC catalogue number 144572. It preserves the external surface of the shell, showing tubercles scattered among finer granules. The palpebral lobe is also clearly defined on the left side of the cranidium.

Onchopeltis curcunchensis Rusconi, Reference Rusconi1955, from the San Isidro region of Argentina, was documented by a drawing of a pygidium (Rusconi, Reference Rusconi1955, pl. 3, fig. 5). Thanks to Dr. Franco Tortello, who reviewed an earlier version of this paper, we have been able to examine photographs of this specimen, as well as an unillustrated specimen that was the basis for a written description of the cranidium (Rusconi, Reference Rusconi1955, p. 34). The photograph demonstrates that the outline and other proportions of the pygidium as depicted in the drawing are generally accurate. However, it is more like pygidia of Dunderbergia (Palmer, Reference Palmer1965, pl. 4. figs. 1, 2) and is much broader (tr.), with a narrower axis and wider pleural fields, than the pygidium of O. spectabilis. Rusconi (Reference Rusconi1955, p. 34) described the cranidium as having a strongly convex and elevated glabella, with two pairs of lateral furrows, the first pair of which are sinuous in outline (“una glabela fuertemente convexa y elevada, con dos surcos glabelares, siendo el posterior de recorrido sinuoso”). The photographs confirm these features and show that the glabellar furrows are deeper than in O. spectabilis. However, the photographs also reveal that the preglabellar field is much longer than in O. spectabilis, and the palpebral lobe is located farther back on the cranidium. We doubt that O. curcunchensis is assigned correctly to the genus, but we leave a full revision to Dr. Tortello.

Onchopeltis anconis new species

Figure 10

1982 Onchopeltis cf. O. spectabilis Rasetti; Kindle, pl. 1.3, figs. 21, 22.

Holotype

A cranidium (GSC 144564, Fig. 10.1–10.3) from the Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland.

Paratypes

A librigena (GSC 144565, Fig. 10.4–10.5) and a cranidium (GSC 144566, Fig. 10.6–10.9) from Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland.

Diagnosis

Librigena with genal spine directed outward and upward; conspicuous deflection of lateral margin of the librigena at base of spine. Cranidium lacks parafrontal band in front of glabella.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Description

Cranidium strongly convex longitudinally and transversely, with conspicuous anterior arch; width at palpebral lobes nearly equal (95%; 90–99%) to length (sag.). Preglabellar and preocular fields dip almost vertically downward to gently sloping anterior border; border accounts for 66% (62–71%) of frontal area length (sag.); anterior border furrow narrow groove. Axial and preglabellar furrows form shallow grooves. Gently tapered, anteriorly rounded glabella with width at S2 equal to 65% (65–66%) of length (sag.); elevated far above palpebral area of fixigena; occupies 80% (79–81%) of cranidial length (sag.) and 55% of cranidial width (tr.) across palpebral lobes. SO curved gently backward, well incised medially, shallow near axial furrow; LO comprises 12% (10–14%) of glabellar length. Two pairs of faint lateral glabellar furrows. S1 weakly incised, geniculate; S2 shallower than S1, curved backward and inward. Palpebral area of fixigena flat to gently inflated, width equal to 41% (39–44%) of glabellar width at S2. Palpebral lobe short flap, length equal to about 25% of preoccipital glabellar length; depressed slightly below rest of palpebral area. Palpebral furrow shallow, arcuate in outline. Palpebral ridge weakly convex, directed forward from palpebral lobe at about 30°. Posterior area of fixigena flexed steeply downward. Anterior branches diverge forward between palpebral lobe and anterior border furrow then curve inward along anterior cranidial margin; posterior branches incompletely preserved but appear to diverge along faintly sigmoid path. Posterolateral projection long (exsag.) at maximum extent, triangular in outline. Posterior border furrow well defined; convex posterior border incompletely preserved, appears to increase in length (exsag.) abaxially. Tuberculate sculpture on glabella and fixigenae, more closely spaced on glabella; fine granules on external surface of anterior border not preserved on internal mold; fine granules also on external surface of preglabellar and preocular fields only, arrayed along weak cecal markings.

Librigena with genal spine directed outward and upward; conspicuous deflection of lateral margin of the librigena at base of spine. Librigenal field dips down to shallow but clearly defined posterior and lateral border furrows; border furrows separated by unfurrowed base of genal spine. Lateral border nearly flat, narrows posteriorly; posterior border weakly convex. Small tubercles on lateral border augmented by granules on external surface. Caecal network on librigenal field with a few indistinct low tubercles.

Etymology

From ancon (Latin), “bend of the arm, elbow,” in reference to the outward deflection of the genal spine.

Remarks

Comparisons between O. anconis and the type species, O. spectabilis, are presented above. Onchopeltis? variabilis Shergold and Webers, Reference Shergold and Webers1992 differs from O. anconis in possessing a strongly inflated, rather than nearly flat, palpebral area of the fixigenae and, consequently, a far less elevated glabella in anterior view (compare Shergold and Webers, Reference Shergold and Webers1992, pl. 4, fig. 7 with Fig. 10.3)

Onchopeltis? sp. 1

Figure 11

Material and occurrence

Two cranidia (GSC 144571, Fig. 11.1–11.3; GSC 144571, Fig. 11.4–11.6) from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

Cranidia Onchopeltis? sp. 1 from HC 202 clearly differ from O. spectabilis and O. anconis in having a much larger palpebral lobe located a little farther back on the cranidium, and they have more widely spaced, larger tubercles on the external surface (Fig.11.5). The preglabellar field is relatively longer and less steeply inclined (Fig. 11.1–11.3). Cranidia of O. anconis (Fig. 10.1–10.3, 10.6–10.8) from HC 166 are much larger than those from HC 202, and there is no overlap in size. We are confident that O. anconis and O.? sp. 1 represent two distinct taxa, although additional material is needed for a definitive evaluation. However, the differences, particularly in the size and position of the palpebral lobe, also lead us to assign the cranidia from HC 202 only questionably to the genus

Genus Glyptometopsis Rasetti, Reference Rasetti1961

Type species

Glyptometopsis tumida Rasetti, Reference Rasetti1961 from the Rocky Springs Station Member, Frederick Limestone, central Appalachians (by original designation).

Diagnosis

Strongly convex glabella, almost parallel-sided, anteriorly rounded. S1 firmly impressed, terminates close to LO without fully isolating L1; S2 and S3 weak, even on internal mold. Palpebral lobe forms narrow (tr.) band. Broad (tr.), short (sag.) semielliptical pygidium. Axis extends to, may merge with, convex posterior border that is raised above pleural field.

Remarks

The type species of Glyptometopsis, G. tumida Rasetti, Reference Rasetti1961, was described from the Frederick Limestone of Maryland. Collections from the Shallow Bay Formation yield a second species, Glyptometopsis parilimba n. sp. (Figs. 12, 13), which is also present in the Gorge Formation of Vermont, albeit misidentified as G. tumida by Clark and Shaw (Reference Clark and Shaw1968). Pygidia (Fig. 13.5–13.10) associated with cranidia of G. parilimba (Fig. 13.4) in HC 166 are broad (tr.) and semielliptical in outline, with an axis that merges with the posterior border. A very similar pygidium (undetermined pygidium number 6 of Rasetti, Reference Rasetti1961, pl. 25, fig. 24) is associated with cranidia of G. tumida in loose blocks of Frederick Limestone at locality ccm/3 (Rasetti, Reference Rasetti1961, p. 107) on the north side of Frederick, Maryland.

Figure 12.

Cranidia of Glyptometopsis parilimba n. sp., boulder 57, Shallow Bay Formation, Cow Head Peninsula, western Newfoundland. (1–4) GSC 143208, holotype: (1) dorsal view; (2) anterior view; (3) lateral view; (4) posterior view. (5–7) GSC 144576, paratype: (5) lateral view; (6) dorsal view; (7) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 12. Long description

Seven photographs of cranidia of Glyptometopsis paralimba. White scale bars represent 1 mm.

Photographs 1–4 show dorsal, anterior, lateral and posterior views, respectively, of the holotype with the GSC catalogue number 143208. The dorsal view (1) show the parallel-sided glabella with deep S1 furrows, and also a row of tubercles in the internal mold of the anterior border furrow. The other three views show that the glabella is strongly convex and stands well above the level of the adjacent fixigenae.

Photographs 5-7 show lateral, dorsal and anterior views of a paratype with the GSC catalogue number 144576. The specimens shows the that the external surface of the shell is smooth aside from a band of terrace ridges on the anterioro border.

*

Figure 13.

Glyptometopsis parilimba n. sp., Shallow Bay Formation, western Newfoundland. (1–3) From boulder 57, Cow Head Peninsula. (4–10) From boulder HC 166, Hickey Cove area. (1–4) Cranidia. (5–10) Pygidia: (1) GSC 144577, paratype, dorsal view. (2) GSC 144578, paratype, dorsal view. (3) GSC 144579, paratype, dorsal view. (4) GSC 144580, paratype, dorsal view. (5–7) GSC 144581, paratype: (5) posterior view; (6) dorsal view; (7) lateral view. (8–10) GSC 144582, paratype: (8) dorsal view; (9) posterior view; (10) lateral view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 13. Long description

Ten photographs of specimens of Glyptometopsis parilimba. White scale bars represent 1 mm.

Photographs 1–4 show dorsal views of paratype cranidia with GSC catalogue numbers 144577, 144578, 144579 and144580, respectively. Each cranidium displays an inflated glabella and a curved anterior border. The external surface of the shell is smooth but the internal mold (3) of the fixigena is finely pitted.

Photographs 5–7 show posterior, dorsal and lateral views, respectively, of a paratype pygidium with the GSC catalogue number 144581. They show a central axis that merges posteriorly with a convex anterior border.

Photographs 8–10 represent dorsal, posterior and lateral views, respectively, of a paratype pygidium with the GSC catalogue number 144582. They show that the axis and border stand well above the level of the pleural field.

The pygidia that we assign to Glyptometopsis invite comparison with the pygidium of Kindbladia (Fig. 14.2, 14.3). They are relatively short and wide in both genera, and similar in outline, with an axis that reaches the posterior border. Glyptometopsis is characterized by a strongly convex border that stands above the pleural field and has a distinct border furrow (Fig. 13.5–13.10). By contrast, Kindbladia lacks a border furrow, with a border that is nearly continuous with the pleural field and defined in part by a band of terrace ridges along the pygidial margin (Fig. 14.3). Compared with the pygidia of species of genera such as Dokimocephalus, Iddingsia, and Plataspella, which have flat to down-sloping borders (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, figs. 10M, N, 12K, L, 15E, F, 19M, N), border morphologies of both Kindbladia and Glyptometopsis may be apomorphic, with pygidial outline and length of the axis as potential synapomorphies supporting a close relationship between them.

Figure 14.

Kindbladia cf. K. affinis (Walcott, Reference Walcott1884) from Nevada. (1) Cranidium OU 239484, dorsal view, Corset Spring Shale, Shingle Pass, collection SHP 18.6 (Westrop et al., Reference Westrop, Waskiewicz and Adrain2007, p. 359–360). Arrows point to small pits in depressions in the anterior border furrow. (2–4) Dunderberg Formation, McGill, Nevada, collection MG 69–70 (Westrop and Adrain, Reference Westrop and Adrain2016, p. 396). (2, 3) Pygidium, OU 239485: (2) dorsal view; (3) posterior view. (4) Cranidium, OU 239486, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 14. Long description

Four photographs of specimens of the trilobite Kindbladia cf. K. affinis for comparison with Glyptometopsis paralimba (Figs. 12, 13) White scale bars represent 1mm.

Photograph 1 shows a dorsal view of a large cranidium with the catalogue number OU 239484 i The glabella has well defined lateral furrows. The palpebral lobe is in the form of a large flap.Three white arrows point to small, distinct pits located within the anterior border furrow at the top of the specimen.

Photograph 2 shows a shows dorsal and posterior views of a pygidium with the catalogue number OU 239485. The specimen is short and wide, with a convex axis and the border is flat.

Photograph 4 shows a dorsal view of a second cranidium with the catalogue number OU 239486. The external surface of the shell is finely granulose, and the palpebral lobes are semielliptical flaps.

In describing Kindbladia, Frederickson (Reference Frederickson1948, p. 802, pl. 123, fig. 23) mentioned the presence of three large oval depressions in the anterior border furrow on the external surface (Fig. 14.4), although not on the internal mold. A well-preserved specimen from Nevada shows that the depressions house small pits (arrows on Fig. 14.1) that are part of an articulation structure between the anterior projection of the librigena and the underside of the cranidium (Adrain and Westrop, Reference Adrain and Westrop2012), which is a character complex used by Adrain (Reference Adrain2011, footnote 33) to define order Olenida. There are faint indications of anterior border furrow depressions on the external surface of some specimens of G. parilimba (Fig. 13.1), but internal molds show three areas of weak (Fig. 13.2) to well-defined (Figs. 12.1, 12.2, 13.3) bands of tubercles on the border furrow in similar positions to the oval depressions in Kindbladia. The tubercles correspond to pits on the underside of the cranidial exoskeleton that record the same articulation structure. However, similar tubercles are not evident in the border furrows of internal molds of cranidia of G. tumida in Rasetti’s (Reference Rasetti1961, pl. 23, figs. 27–33) photographs and are not mentioned in his (Rasetti, Reference Rasetti1961, p. 113) description. This records an apparent case of interspecific variation in the expression of the pits. It remains to be seen whether the complementary pillars on the librigena (Adrain and Westrop, Reference Adrain and Westrop2012) are present in G. tumida, but this will require information from silicified sclerites.

The glabella of Glyptometopsis is nearly parallel-sided (Figs. 12.1–12.7, 13.1–13.4; Rasetti, Reference Rasetti1961, pl. 23, figs. 27, 28, 33), whereas a tapered, more conical glabella, which is the alternate, probably plesiomorphic, state, is found in Kindbladia (Fig. 14.1, 14.4) and other dokimocephalids such as Dokimocephalus (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 4A, H, J, N) and Iddingsia (Westrop et al. Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 16A, D, G–I). Among other cranidial characters of Glyptometopsis, the relatively long, well-incised S1 furrow that terminates close to SO may be apomorphic. By contrast, S1 furrows of cranidia of Kindbladia (Fig. 14.1, 14.4) end farther from SO, resembling the condition in such genera as Dokimocephalus (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 10A–I) and Iddingsia (Westrop et al. Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 16A–K), and we interpret this state as plesiomorphic. The palpebral lobes of both species of Glyptometopsis are narrow (tr.) bands (Figs. 12.6, 13.1; Rasetti, Reference Rasetti1961, pl. 23, figs. 27, 28), and this state may also be apomorphic. Kindbladia has larger, more arcuate palpebral lobes (Fig. 14.1, 14.4), which are matched in, for example, Dokimocephalus (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 12 C, D, G, J), Iddingsia (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 15A, L), and Plataspella (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 19I, J), and this is likely to be the plesiomorphic state.

Glyptometopsis parilimba new species

Figures 12, 13

Reference Clark and Shaw1968 Glyptometopsis tumida Rasetti; Clark and Shaw, p. 388, pl. 54, figs. 20–25.

Reference Westrop and Engel2023 Glyptometopsis cf. G. tumida Rasetti; Westrop and Engel, fig. 3j.

Holotype

A cranidium (GSC 143208, Fig. 12.1–12.4) from the Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland.

Paratypes

Four cranidia from boulder CH 57 (GSC 144576, Fig. 12.5–12.7; GSC 144577, Fig. 13.1; GSC 144578, Fig. 13.2; GSC 144579, Fig. 13.3). One cranidium (GSC 144580, Fig. 13.4) and two pygidia (GSC 144581, Fig. 13.5–13.7; GSC 144582, Fig. 13.8–13.10) from boulder HC 166, Hickey Cove area.

Additional material

In addition to the figured specimens, one cranidium from CH 57 and three cranidia from HC 166 were complete enough to provide measurements.

Diagnosis

A species of Glyptometopsis with frontal area divided subequally into preglabellar field and convex anterior border. Three bands of tubercles on internal mold of anterior border furrow, one medially and two laterally. Pygidial border nearly transverse behind axis. Aside from shallow pleural furrow at anterior, pleural field unfurrowed.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head and boulder HC 166, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Description

Cranidium roughly semielliptical in outline, length (sag) equal to 92% (85–95%) of width across palpebral lobes, with curved anterior margin; strongly arched longitudinally and transversely. Preglabellar field inflated, occupies a little more than half (54%; 51–56%) of frontal area length; arcuate, convex anterior border maintains nearly even width (sag., exsag.), protrudes slightly beyond preglabellar field in lateral view (Fig. 12.5); anterior border furrow narrow groove. Three bands of tubercles on internal mold of anterior border furrow, one medially and two laterally (Figs. 12.1, 13.3). Axial and preglabellar furrows gently impressed. Glabella strongly convex, stands well above palpebral area of fixigenae, accounts for 78% (76–81%) of cranidial length; nearly parallel-sided with well-rounded anterior margin. SO firmly impressed, nearly transverse medially, deflected forward and narrowing (exsag.) near glabellar margin. LO with posterior margin gently curved medially, curving strongly forward abaxially; comprises 15% of glabellar length (sag.); small median node near anterior margin (Fig. 13.1). Three pairs of lateral glabellar furrows. S1 oblique with gently curved adaxial terminus; deep on external surface and internal mold, connects with axial furrow. L1 comprises 21% (16–25%) of glabellar length (exsag.) at axial furrow. S2 oblique to geniculate, faint at best on external surface, barely incised on internal mold. L2 shorter than L1, length (exsag.) at axial furrow equal to 15% (13–16%) of glabellar length. S3 not expressed on external surface; barely perceptible on internal mold, nearly transverse. Palpebral area of fixigena weakly inflated, broad (tr.), width equal to 61% of glabellar width at L2. Palpebral lobe gently curved, nearly flat, length equal to 30% (27–32%) of glabellar length; centered near midpoint of L2. Palpebral furrow firmly impressed groove. Palpebral ridge curves forward to intersect axial furrow near S3. Anterior branches of facial sutures nearly parallel between palpebral lobes and anterior border furrow before curving along anterior cranidial margin. Posterior branches diverge gradually along curved paths. Posterior margin of posterior area transverse near glabella, deflected backward abaxially. Maximum length (exsag.) of posterolateral projection equal to 28% (27–32%) of cranidial length, maximum width (tr.) equal to 9% (8–10%) of cranidial width across posterior margin. Posterior border furrow deep; posterior border convex; both expand (exsag.) abaxially. Terrace ridges present along anterior half of anterior border; remainder of external surface smooth. On internal mold, fixigenal field punctate (Fig. 12.1).

Semielliptical pygidium short (sag.) and wide (tr.), length equal to 40% of width; slight arch of posterior margin behind axis (Fig. 13.5, 13.9). Axis convex, long, occupies 80% of pygidial length, merges with posterior border (Fig. 13.6); width at first axial ring equal to 35% of pygidial width; tapers backward, width at posterior tip equal to about 60% of width at first ring. Articulating half-ring incompletely preserved. One axial ring separated from long terminal piece by transverse ring furrow; anterior part of terminal piece with slight independent convexity. Pleural field depressed below border. Shallow pleural furrow at anterior and one gently convex pleural band; remainder of pleural field unfurrowed. Border convex, nearly transverse and widest behind axis, narrowing as approaches anterior corner of pygidium. Exoskeleton not preserved; internal mold appears smooth.

Etymology

From pars (Latin), “equal,” and limbus (Latin), “border,” in reference to the division of the frontal area into a preglabellar field and anterior border that are nearly equal in length.

Remarks

Cranidia of Glyptometopsis parilimba n. sp. are differentiated most readily from those of the type species, G. tumida, by the proportions of the frontal area. Glyptometopsis tumida is characterized by a relatively narrow (sag., exsag.), weakly convex anterior border occupying about one-third of frontal area length (Rasetti, Reference Rasetti1961, pl. 23, figs. 28–30); in lateral view, the border continues the slope of the preglabellar field with little interruption (Rasetti, Reference Rasetti1961, pl. 23, figs. 30, 31). In G. parilimba, the border is almost as long as the preglabellar field (Fig. 12.1–12.3) and is more convex, protruding to form a distinct ledge beneath the preglabellar field in lateral view (Fig. 12.5).

Cranidia from the Gorge Formation of Vermont that were assigned to G. tumida by Clark and Shaw (Reference Clark and Shaw1968, pl. 54, figs. 20–25) possess long, convex borders and are transferred to G. parilimba. Internal molds of G. parilimba from the Shallow Bay Formation possess tubercles in the anterior border furrow (Fig. 12.1) that, as noted above, are not present in the type material of G. tumida from Maryland. Part of the frontal area is exfoliated in one of the cranidia from Vermont illustrated by Clark and Shaw (Reference Clark and Shaw1968, pl. 54, fig. 22). There is no sign of tubercles in the border furrow, possibly because preservation of this part of the sclerite appears to be poor. Indeed, tubercles can be weakly expressed even in well-preserved cranidia of G. parilimba from the Shallow Bay Formation (Fig. 13.2), and we include the presence of tubercles in the diagnosis of the species.

The pygidial border is nearly transverse behind the axis in G. parilimba (Fig. 13.6, 13.8), but it is curved forward to meet the axis in G. tumida (Rasetti, Reference Rasetti1961, pl. 25, fig. 24). Glyptometopsis tumida also has two pairs of deep pleural furrows on the pleural field, whereas G. parilimba has only one shallow pair of furrows at the anterior.

Theokritoff (Reference Theokritoff1984) illustrated two cranidia from the Taconic succession in eastern New York that he assigned to different species of Glyptometopsis, but it is doubtful that these identifications are correct. Glyptometopsis sp. indet. 1 (Theokritoff, Reference Theokritoff1984, fig. 1S, T) has a weakly convex, more-tapered glabella, shallow S1 furrows, and narrow (tr.) fixigenae. Glyptometopsis sp. indet. 2 (Theokritoff, Reference Theokritoff1984, fig. 1U, V) has a strongly convex glabella, but it is anteriorly truncate. Moreover, the S1 furrows are shallow and terminate well short of SO. Finally, the palpebral lobe is wider, located closer to the glabella, and somewhat farther forward.

Genus Bellaspidella Rasetti, Reference Rasetti1945

Type species

Bellaspidella resseri Rasetti, Reference Rasetti1945 from the Lévis Formation of Quebec (by original designation).

Diagnosis

Frontal area short, with preglabellar field very short or absent. S1 furrow oblique and well incised. Palpebral lobe centered opposite L2.

Remarks

Two species from HC 166, Bellaspidella crocalae n. sp. (Fig. 15.1–15.10) and Bellaspidella cf. B. longifrons Clark in Clark and Shaw, Reference Clark and Shaw1968 (Fig. 16.1–16.10), are assigned to the genus on the basis of characters that they share with the type species, B. resseri Rasetti, Reference Rasetti1945. These characters include a very short frontal area with a gently upturned anterior border and a slot-like border furrow that is tangential, or nearly so, to the preglabellar furrow. S1 glabellar furrows are well defined, but other lateral furrows are faint, even on internal molds. The palpebral lobe is centered opposite the L2 lateral glabellar lobe.

Figure 15.

Cranidia of Bellaspidella crocalae n. sp., boulder HC 166, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1–3) GSC 144583, holotype: (1) dorsal view; (2) lateral view; (3) anterior view. (4) GSC 144584, paratype, dorsal view. (5–7) GSC 144585, paratype: (5) dorsal view; (6) lateral view; (7) anterior view. (8–10) GSC 144586, paratype: (8) lateral view; (9) dorsal view; (10) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 15. Long description

Ten photographs of cranidia of Bellaspidella crocalae. White scale bars represent 1 mm.

Photographs 1–3 show dorsal, lateral and anterior views, respectively, of the holotype cranidium with the GSC catalogue number 144583. The dorsal view (1) shows the glabella with well defined, oblique S1 furrows. Panel 2 is a lateral view showing the profile curvature. Panel 3 is an anterior view showing the frontal arch.

Photograph 4 shows a dorsal view of a paratype cranidium with the GSC catalogue number 144584. It features a short, upturned anterior border.

Photographs 5–7 show dorsal, lateral and anterior views of a paratype crandium with the GSC catalogue number 144585. This specimen is smaller than the other specimens, and has a shorter frontal area.

Photographs 8–10 show lateral, dorsal and anterior views, respectively, of a paratype cranidium with the GSC catalogue number 144586. The glabella is slightly shorter and wider than those of the other specimens.

Figure 16.

Cranidia of Bellaspidella cf. B. longifrons (Clark in Clark and Shaw, Reference Clark and Shaw1968). (1–7) From boulder HC 166, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (8–10) From boulder 57, Cow Head Peninsula. (1–3) GSC 144587: (1) lateral view; (2) dorsal view; (3) anterior view. (4–6) GSC 144588: (4) anterior view; (5) dorsal view; (6) lateral view. (7) GSC 144589, dorsal view. (8–10) GSC 144590: (8) dorsal view; (9) lateral view; (10) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 16. Long description

Ten photographs of cranidia of Bellaspidella cf. B. longifrons. White scale bars represent 1 mm.

Photographs 1–3 show lateral, dorsal and anterior views, respectively, of a specimen with the GSC catalogue number 144587. The front of the specimen is broken but it shows the narrow fixigena that distinguishes the species from B. crocalae (Fig. 15).

Photographs 4–6 show lateral, dorsal and anterior views, respectively of a specimen with the GSC catalogue number 144588.The dorsal view (5) shows the prominent glabella with deep S1 furrows. The lateral view (6) shows the short but steeply sloping frontal area, whereas the anterior view (4) exemplifies the convexity of the glabella and the anterior cranidial arch.

Photograph 7 shows a dorsal view of a specimen with the GSC catalogue number 144589, displaying a well-preserved anterior border.

Photographs 8–10 show dorsal, lateral and anterior views, respectively, of a relatively smallspecimen with the GSC catalogue number 144590. The dorsal view (8) shows the narrow fixigena, centrally positioned palpebral lobe, and a medial occipital tubercle. The lateral (9) and anterior (10) views convey the convexity of the specimen.

-

It is now apparent that Ludvigsen and Westrop in Ludvigsen et al. (Reference Ludvigsen, Westrop and Kindle1989, p. 23, pl. 13, figs. 1–8) combined two distinct taxa in their revision of B. resseri. The holotype (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, fig. 1) from Quebec is incomplete but has a short frontal area with a gently curved anterior border and very short preglabellar field, and a firmly impressed S1. Three cranidia from Newfoundland (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 2–5) appear to record B. resseri. However, two other cranidia (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 6–8) are characterized by a more strongly curved border, and the border furrow merges with the preglabellar furrow. In addition, the S1 furrow is deeper than in other cranidia assigned to B. resseri, and the palpebral lobe appears to be smaller. We consider these two cranidia to represent an undescribed species, which we will refer to as Bellaspidella aff. B. resseri. They are even closer to B. crocalae and Bellaspidella cf. B. longifrons in morphology of the frontal area.

Other species of Bellaspidella have short but clearly defined preglabellar fields, including B. sulcata (Rasetti, Reference Rasetti1945) (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 9–11) and B. logani Ludvigsen and Westrop in Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989 (pl. 13, figs. 15–18). Bellaspidella foveolata (Rasetti, Reference Rasetti1943) (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 12–14) is known from only two incomplete cephala that possess a short preglabellar field but also an S1 furrow that is faint at best. If the species is correctly assigned to Bellaspidella, the nearly effaced S1 is an autapomorphy.

Adrain and Fortey (Reference Adrain and Fortey1997) compared B. parallela Ludvigsen and Westrop in Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989 (pl. 13, figs. 19–25) with Agerina norrisi Ludvigsen, Reference Ludvigsen1980 and some related species. In a subsequent evaluation, Karim and Adrain (Reference Karim and Adrain2022) established a new genus, Forteyaspis, which included A. norrisi. They were uncertain about a relationship between Forteyaspis or Agerina and B. parallela because the latter lacked such characters as a bifurcate S1 lateral glabellar furrow. They did, however, exclude the species at least temporarily from what they termed the “Agerina group” until more information becomes available.

Bellaspidella parallela is the only member of the genus to which a pygidium has been assigned, and pygidial anatomy was an important part of the generic diagnosis proposed by Ludvigsen and Westrop in Ludvigsen et al. (Reference Ludvigsen, Westrop and Kindle1989, p. 23). Because of the uncertainties about the relationships of this species, we present a revised diagnosis based only on cranidial characters. It includes the presence of a well-incised S1 furrow, which is similar to the condition of S1 in Glyptometopsis. In other respects, particularly morphology of the frontal area, Bellaspidella and Glyptometopsis are quite different, and we interpret the similarity in S1 as a case of parallel acquisition rather than retention of a plesiomorphic state.

Bellaspidella crocalae new species

Figure 15

Holotype

A cranidium (GSC 144583, Fig. 15.1–15.3) from the Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland.

Paratypes

Three cranidia (GSC 144584, Fig. 15.4; GSC 144585, Fig. 15.5–15.7; GSC 144586, Fig. 15.8–15.10) from the Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland.

Diagnosis

Wide (tr.) palpebral area of fixigena equal to 45% of glabellar width at L2. Very short (sag.) frontal area with slot-like anterior border furrow tangential to preglabellar furrow. Gently curved anterior cranidial arch.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Description

Excluding posterolateral projection, cranidium crudely rectangular in outline, with curved anterior margin; strongly convex in lateral (Fig. 15.2) and anterior (Fig. 15.3) profiles. Frontal area short with steeply sloping preglabellar and preocular fields; upturned anterior border occupies about one-third (32%; 30–33%) of frontal area length in larger cranidia (Fig. 15.1) but is proportionately longer in smaller cranidia (Fig. 15.5), accounting for more than 50% of frontal area length (53%; 50–57%). Glabella strongly convex, standing well above palpebral area of fixigena, slightly tapered, posteriorly rounded; comprises 87% (85–88%) of cranidial length, 52% of cranidial width across palpebral lobes. SO well incised, nearly transverse and widest (sag., exsag.) medially but narrows and deflected forward near glabellar margin. LO with posterior margin curved gently backward, length equal to 12% (11–14%) of glabellar length. Geniculate S1 firmly impressed, deeper on internal mold than on external surface of exoskeleton. L1 accounts for 27% (24–31%) of glabellar length. S2 much shallower than S1 on both external surface and internal mold, gently curved backward and inward. L2 shorter than L1, length (exsag.) near glabellar margin equal to 18% (16–20%) of glabellar length. Palpebral area weakly inflated, wide, width (tr.) equal to 45% (44–45%) of glabellar width at L2. Palpebral lobe nearly flat, arcuate, length equal to 29% (26–32%) of glabellar length; palpebral furrow clearly defined curved groove. Palpebral ridge weakly convex, runs obliquely forward to intersect axial furrow in front of S2. Anterior branches of facial suture gently divergent between palpebral lobe and anterior border before proceeding along curved anterior margin. Posterior branches diverge along nearly straight paths. Posterior area of fixigena flexed downward with similar slope to preocular field. Maximum length (exsag.) of posterolateral projection equal to 25% of cranidial length; maximum width (tr.) equal to 17% (16–17%) of cranidial width at posterior margin. Posterior border furrow well incised, expands (exsag.) abaxially; posterior border convex, maintains nearly uniform length (exsag.) over entire width (tr.). External surface of exoskeleton granulose; internal mold smooth.

Etymology

From krokale (Greek), “beach, seashore,” in reference to the occurrence of this species in a boulder from conglomerates exposed on the shore near Hickey Cove.

Remarks

Bellaspidella crocalae n. sp. is most like Bellaspidella cf. B. longifrons (Fig. 16.1–16.10), which also occurs in HC 166. The most striking difference lies in the greater width (tr.) of the palpebral area of the fixigena of B. crocalae, which is equal to 45% of glabellar width at L2, but that value drops to 30% in Bellaspidella cf. B. longifrons. Other species of Bellaspidella, including B. resseri (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 1–5), Bellaspidella aff. B. resseri (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 6–8; see Remarks section for Bellaspidella, above), B. sulcata (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 9–11), B. foveolata (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 12–14), and B. logani (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 15–18), also have much narrower palpebral areas than B. crocalae.

Bellaspidella crocalae has a weak anterior cranidial arch throughout holaspid ontogeny (Fig. 15.3, 15.7, 15.10), whereas at least larger specimens of Bellaspidella cf. B. longifrons have a stronger arch (Fig. 16.4). Other species of Bellaspidella lack an arch entirely (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs. 3, 7, 11, 13, 16). Like B. crocalae, Bellaspidella aff. B. resseri lacks a preglabellar field but differs in having a much more strongly curved anterior border (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs 6–8). Several species possess a short preglabellar field, including B. resseri, B. sulcata, B. foveolata, and B. logani (Ludvigsen et al., Reference Ludvigsen, Westrop and Kindle1989, pl. 13, figs.1–3, 9–17).

Bellaspidella cf. B. longifrons (Clark in Clark and Shaw, Reference Clark and Shaw1968)

Figure 16.1

cf. Reference Clark and Shaw1968 Bellaspis longifrons Clark in Clark and Shaw, p. 388, pl. 54, figs. 17–19.

Material and occurrence

Downes Point Member, Shallow Bay Formation. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna. Figured material consists of three cranidia (GSC 144587, Fig. 16.1–16.3; GSC 144588, Fig. 16.4–16.6; GSC 144589, Fig. 16.7) from HC 166 and one cranidium (GSC 144590, Fig. 16.8–16.10) from CH 57. Two additional cranidia from HC 202 were complete enough to provide measurement data.

Remarks

The type species of Bellaspis Rasetti, Reference Rasetti1945, B. billingsi Rasetti, Reference Rasetti1945, is known from only two figured cranidia (Rasetti, Reference Rasetti1945, pl. 60, figs. 34–36). Ludvigsen and Westrop in Ludvigsen et al. (Reference Ludvigsen, Westrop and Kindle1989, p. 23) were uncertain about the status of this genus because several aspects of the cranidial anatomy, including the convex transverse anterior border, resemble small specimens of the lecanopygid Rasettia Lochman, Reference Lochman1953. In any event, Bellaspis longifrons Clark in Clark and Shaw, Reference Clark and Shaw1968, named for a single cranidium with a damaged glabella from the Gorge Formation (Clark and Shaw, Reference Clark and Shaw1968, pl. 54, figs. 17–19) seems misassigned. Bellaspis billingsi has a small palpebral lobe whose anterior end is extended forward in what appears to be a short (tr.) but stout palpebral ridge that reaches the axial furrow (Rasetti, Reference Rasetti1945, pl. 60, fig. 34), isolating the palpebral area from the preocular field. A palpebral ridge is not present in B. longifrons, and the fixigenae are continuous between the palpebral area and preocular field. In addition, the S1 furrow of B. longifrons is much deeper, and S2 shallower; the preglabellar field is barely expressed but is well developed in B. billingsi. These various differences ally Clark’s (Clark in Clark and Shaw, Reference Clark and Shaw1968) species with Bellaspidella rather than Bellaspis.

Cranidia from CH 57, HC 166, and HC 202 are very similar to the holotype of Bellaspidella longifrons, differing only in a longer (exsag.) palpebral lobe and a slightly wider (tr.) palpebral area. Because comparisons with Bellaspidella longifrons are limited to the holotype, we place the material from the Shallow Bay Formation in open nomenclature.

Bellaspidella? cf. B. foveolata (Rasetti, Reference Rasetti1943)

Figure 17.1–17.6

Figure 17.

Cranidia from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland. (1–6) Bellaspidella? cf. B. foveolata (Rasetti, Reference Rasetti1943). (1–3) GSC 144573: (1) dorsal view; (2) lateral view; (3) anterior view. (4–6) GSC 144574: (4) anterior view; (5) lateral view; (6) dorsal view. (7–9) Prosaukia? aff. P. hartti (Walcott, Reference Walcott1879), GSC 144575: (7) dorsal view; (8) lateral view; (9) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 17. Long description

Nine photographs displaying cranidia of two different species. White scale bars represent 1 mm.

Photographs 1–6 are cranidia of Bellaspidella cf. B. foveolata 1–3 show dorsal, lateral and anterior views, respectively, of a specimen with the GSC catalogue number 144573. The dorsal view (1) shows the forwardly expanding frontal area, narrow fixigena, and the conspicuous glabella. The lateral (2) and dorsal (3) views convey the overall convexity of the specimen.

Photographs 4–6 show anterior, lateral and dorsal views, respectively, of a small specimen with the GSC catalogue number 144574. It has well developed furrows on the glabella.

Photographs 7–9 show a dorsal, lateral and anterior views, respectively of a cranidium of Prosaukia? aff. P. hartti. with the GSC catalogue number 144575. The dorsal view (7) shows S1 furrows that are connected across the glabella and a relatively small palpebral lobe. The lateral view (8) shows the convexity of the specimens, whereas the anterior view displays the anterior border.

cf. Reference Rasetti1943 Onchonotus foveolatus Rasetti, p. 103, pl. 19, figs. 4–6.

?Reference Rasetti1961 Undetermined cranidium no. 2 Rasetti, p. 119, pl. 23, figs. 35, 36.

cf. Reference Ludvigsen, Westrop and Kindle1989 Bellaspidella foveolata (Rasetti); Ludvigsen et al., p. 23, pl. 13, figs. 12–14.

Material and occurrence

Downes Point Member, Shallow Bay Formation, Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna. Two cranidia (GSC 144573, Fig. 17.1–17.3; GSC 144574, Fig. 17.4–17.6) from boulder HC 202, Hickey Cove area, western Newfoundland.

Remarks

Cranidia from HC 202 (Fig. 17.1–17.6) may be related to the specimen illustrated by Rasetti (Reference Rasetti1961, pl. 23, figs. 35, 36) under the name “undetermined cranidium no. 2.” All of these cranidia share divergent anterior branches of the facial sutures and a long, nearly flat anterior border separated from the preglabellar field mostly by a change in slope. Incision of the lateral glabellar furrows is similar in the larger of our two specimens (Fig. 16.1–16.3) and in undetermined cranidium no. 2. The surfaces of both cranidia from HC 202 are finely granulose as is apparently the case for undetermined cranidium 2 (Rasetti, Reference Rasetti1961, p. 120). The only difference lies in the larger palpebral lobes of our specimens and stronger divergence of the anterior branches of the facial sutures.

Aside from the longer border and divergent anterior sutures, our specimens resemble Bellaspidella foveolata in possessing weak glabellar furrows and a short preglabellar field and in the size and position of the palpebral lobe; they are assigned questionably to that genus. Although it is likely that they record a new species, we use open nomenclature because of the limited sample size, which is exacerbated by damage to the frontal area of our larger specimen.

In addition to having far-less-divergent anterior branches of the facial sutures, Bellaspidella aff. B. faveolata (sic), from the Jones Ridge Limestone of Alaska (Taylor et al., Reference Taylor, Strauss and Repetski2025, fig. 14A–H), has a longer, more convex preglabellar field and a shorter, more angular anterior border than cranidia from HC 202.

Family Aphelaspididae Palmer, Reference Palmer1960

Genus Eugonocare Whitehouse, Reference Whitehouse1939

Type species

Eugonocare tesselatum Whitehouse, Reference Whitehouse1939 from the Georgina Limestone of Queensland, Australia (by original designation).

Remarks

Henderson (Reference Henderson1976) diagnosed Eugonocare on the basis of a cranidium whose width across the palpebral lobes exceeds the sagittal length and an aspinose pygidium. He did, however, note that some species of Olenaspella Wilson, Reference Wilson1956 resembled Eugoncare in cranidial morphology but possessed pygidial spines. Subsequent studies (Peng, Reference Peng1992; Pratt, Reference Pratt1992) emphasized that Olenaspella and Pseudeugonocare Peng, Reference Peng1992 are very similar in cranidial morphology, and they focused on pygidial morphology as a source of diagnostic characters.

Pratt (Reference Pratt1992) revised Eugonocare and Olenaspella and transferred species between them. He noted that the pygidial spines of the type species of Olenaspella, O. evansi (Kobayashi, Reference Kobayashi1936a), and O. regularis Palmer, Reference Palmer1962 were extensions of the pleurae. The anterior and posterior pleural bands and the pleural furrow extend onto the anteriormost spine in both species (Palmer, Reference Palmer1962, pl. 5, figs. 2, 5; Pratt, Reference Pratt1992, pl. 16, figs. 5–7, 28, 29). However, O. separata Palmer, Reference Palmer1962 has spines developed from the posterior border of a relatively long pygidium, and the pleural furrows and bands extend no farther than the border furrow (Palmer, Reference Palmer1962, pl. 5, figs. 15–19, 24). In recognition of this difference in morphology, Pratt transferred O. separata to Eugonocare. Character polarities for the alternate spine configurations will obviously depend on the choice of outgroup. Comparison with, for example, pygidia of Aphelaspis Resser, Reference Resser1935 (Palmer, Reference Palmer1965, pl. 8, figs. 15, 19, 26) suggests that absence of spines is the plesiomorphic condition. Wilson (Reference Wilson1954, p. 250) noted similarities between Aphelaspis and older (Guzhangian) genera assigned to family Andrarinidae Raymond, Reference Raymond1937, including Groenwallia Kobayashi, Reference Kobayashi1935 and Nericia Westergård, Reference Westergård1948. Henningsmoen (Reference Henningsmoen1957) suggested that Eugonocare might belong in Andrarinidae and considered the family to be a possible relative of Olenidae Burmeister, Reference Burmeister1843. Palmer (Reference Palmer1960, p. 80) placed Nericia in family Pterocephaliidae Kobayashi, Reference Kobayashi1935 but left it unassigned at the subfamily level. There are sufficient similarities between cranidia of Nericia and Aphelaspis to entertain the possibility that Andrarinidae and Aphelaspididae are sister taxa. These similarities include a weakly furrowed, tapered, bluntly rounded glabella and a long, gently upturned border (Westergård, Reference Westergård1948, pl. 4, figs. 6a, b, 7). Andrarina itself has a narrow, aspinose pygidial border (Westergård, Reference Westergård1948, pl. 3, fig. 23, pl. 4, fig. 3), whereas Nericia has a set of small spines that originate from the margin of the border, much like the longer spines in Eugonocare separatum. We conclude that the spine morphology of species of Olenaspella as revised by Pratt is the apomorphic condition and that this genus is likely monophyletic.

Peng (Reference Peng1992) also focused on spinosity as a diagnostic character and reached somewhat different conclusions from Pratt. Peng (Reference Peng1992) restricted Eugonocare to species with aspinose pygidia, with Olenaspella comprising species with one to three spines. He also proposed a new taxon, Pseudeugoncare, that was diagnosed by an expanded border that carries a single pair of stout, broad-based spines, characters that by comparison with Nericia and Olenaspella are probably apomorphic. Peng classified Olenaspella, Eugonocare, and Pseudeugonocare as subgenera of Eugonocare although the implied polytomous cladogram seems unlikely, and we prefer to treat them as separate genera.

Olenaspella, as revised by Pratt (Reference Pratt1992), and Pseudeugonocare are probably monophyletic on the basis of pygidial spine anatomy. Pygidia of species currently assigned to Eugonocare mostly lack marginal spines although some possess slender spines originating from the border. These states are likely to be plesiomorphic. Pratt (Reference Pratt1992) emphasized the relatively long pygidium with an axis that includes five to seven axial rings in his diagnosis of Eugonocare (Henderson, Reference Henderson1976, pl. 49, fig. 18; Shergold, Reference Shergold1982, pl. 17, fig. 2; Pratt, Reference Pratt1992, pl. 17, figs. 5, 7, 8). However, a long pygidium with more than five axial rings in the axis is also a characteristic of Pseudeugonocare (Peng, Reference Peng1992, fig. 31C, 31E, F, 31I), and the pygidium of the type species of Eugonocare, E. tessellatum, has a relatively short pygidium Shergold, Reference Shergold1982, pl. 10, figs. 5, 7, 8).

Support for monophyly of Eugonocare from pygidial characters seems equivocal at best, and cranidia have not yet provided unambiguous evidence. As noted by Henderson (Reference Henderson1976), cranidia of Eugonocare are relatively wide (tr.). However, as recognized by Peng (Reference Peng1992) and Pratt (Reference Pratt1992), wide cranidia are also characteristic of Olenaspella and Pseudeugonocare. Cranidia of E. tessellatum illustrated by Shergold (Reference Shergold1982, pl. 10, figs. 2, 3) have very long (exsag.), broad (tr.) palpebral lobes. Similar palpebral lobes are also present in, for example, E. whitehousei Henderson, Reference Henderson1976 (Shergold, Reference Shergold1982, pl. 17, figs. 1, 5) and E. arquatum n. sp. from the Shallow Bay Formation (Fig. 18.3, 18.4). Although this character state contrasts with smaller palpebral lobes in Aphelaspis (Palmer, Reference Palmer1965, pl. 8, figs. 14, 18, 25) and andrarinids like Nericia (Westergård, Reference Westergård1948, pl. 4, figs. 6, 7) and Andrarina (Westergård, Reference Westergård1948, pl. 4, fig. 1), it is unlikely to be a synapomorphy for more than a subset of species currently assigned to Eugonocare. For example, cranidia from the Dolodrook River limestones of Victoria, Australia, attributed to E. tessellatum by Paterson and Laurie (Reference Paterson and Laurie2004, fig. 9A–F) have much smaller palpebral lobes than those illustrated by Shergold (Reference Shergold1982), to the extent that we doubt that they record the same species. However, in other respects, they are similar to E. tessellatum and appear to record a relatively small-eyed species. At the current state of knowledge, there do not appear to be any unequivocal cranidial or pygidial synapomorphies on which to base Eugonocare, and the genus may well be paraphyletic. It is used here with reservation. We are also mindful that published diagnoses of Aphelaspis are essentially descriptive (Palmer, Reference Palmer1965; Pratt, Reference Pratt1992), and it is far from clear as to whether they include apomorphic character states that might indicate monophyly. If Aphelaspis also proves to be paraphyletic, this could well have implications for classification of species of Eugonocare. These issues underscore the need for a comprehensive phylogenetic analysis of Aphelaspididae.

Figure 18.

Cranidia of “Eugonocare” arquatum n. sp., boulder HC 202, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1–3) GSC 144591, holotype: (1) anterior view; (2) lateral view; (3) dorsal view. (4, 5) GSC 144592, paratype: (4) dorsal view; (5) anterior view. (6) GSC 144593, paratype, dorsal view. (7–9) GSC 144594, paratype: (7) dorsal view; (8) lateral view; (9) anterior view. (10–12) GSC 145072, paratype: (10) anterior view; (11) lateral view; (12) dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 18. Long description

Twelve photographs of cranidia of "Eugonocare" arquatum. White scale bars represent 1 mm.

Photographs 1–3 show anterior, lateral and dorsal views, respectively, of the holotype with the GSC catalogue number 144591. The dorsal view (3) shows the curved anterior border and the trapezoidal glabella. The anterior (1) and lateral (2) views show the convexity of the specimen.

Photographs 4, 5 show dorsal and anterior views of a paratype with the GSC catalogue number 144592. Both views show the size and orientation of the palpebral lobes.

Photograph 6 shows a dorsal view of a paratype with the GSC catalogue number 144593. i It shows the long frontal area and the lateral furrows of the glabella.

Photographs 7–9 show dorsal, lateral and anterior views, respectively, of a slightly damaged paratype with the GSC catalogue number 144594.

Photographs 10–12 show anterior, lateral and dorsal views, respectively, of paratype with the GSC catalogue number 145072. It features well developed palpebral ridges that are shown clearly in the anterior (10) and dorsal (12) views.

“Eugonocare” arquatum new species

Figures 18, 19

Figure 19.

“Eugonocare” arquatum n. sp., boulder HC 202, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1–3, 7–9) Cranidia. (4–6) Pygidia. (1–3) GSC 144595, paratype: (1) dorsal view; (2) lateral view; (3) anterior view. (4) GSC 144596, paratype, dorsal view. (5, 6) GSC 144597, paratype: (5) dorsal view; (6) posterior view. (7–9) GSC 144598, paratype): (7) dorsal view; (8) anterior view; (9) lateral view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 19. Long description

Nine photographs of cranidia and pygidia of "Eugonocare" arquatum. White scale bars represent 1 mm.

Photographs 1–3 show dorsal, lateral and anterior views, respectively, of a paratype cranidium with the GSC catalogue number 144595. It features a well developed palpebral lobe, shown clearly in the dorsal and anterior views.

Photograph 4 shows a dorsal view of a paratype cranidium with the GSC catalogue number 144596. The central axis and axial rings are clearly visible.

Photographs 5, 6 show dorsal and posterior views of a paratype pygidium with the GSC catalogue number144597. The dorsal view (5) displays the overall outline of the specimen, and the posterior view (6) demonstrates the convexity, with the axis elevated well above the pleural field.

Photographs 7–9 show dorsal, anterior and lateral views, respectively of a large paratype cranidium with the GSC catalogue number 144598. The dorsal view (8) emphasizes the very long frontal area, and the lateral view (9) show the forward slope of this feature.

Holotype

A cranidium (GSC 144591, Fig. 18.1–18.3) from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland.

Paratypes

All paratypes are from boulder HC 202. Six cranidia (GSC 144592, Fig. 18.4, 18.5; GSC 144593, Fig. 18.6; GSC 144594, Fig. 18.7–18.9; GSC 145072, Fig. 18.10–18.12; GSC 144595, Fig. 19.1–19.3; GSC 144598, Fig. 19.7–19.9) and two pygidia (GSC 144596, Fig. 19.4; GSC 144597, Fig. 19.5, 19.6).

Diagnosis

Frontal area divided into very long preglabellar field, equal to 26% (23–29%; higher values in smaller specimens; compare Fig. 19.1 with Fig. 19.7) of cranidial length and shorter, strongly curved anterior border.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Description

Cranidium vaguely hourglass-shaped in outline with both anterior portion and shorter posterior portion expanding outward; anterior margin curved strongly forward; width (tr.) across palpebral lobe equal (102%; 96–106%) to cranidial length (sag.). Frontal area long, occupying 36% (34–40%; higher values in larger specimens; Fig. 19.7) of cranidial length (sag.). Gently inflated preglabellar field accounts for 71% (66–73%) of frontal area length; anterior border nearly flat (Fig. 18.2), strongly curved, longest (sag.) medially, shortening abaxially (Fig. 18.6); anterior border furrow firmly impressed. Axial and preglabellar furrows clearly defined grooves. Glabella weakly arched in anterior and lateral views; tapers gently forward, trapezoidal in outline with slight forward curvature of anterior margin. SO nearly transverse medially, curving gently forward and shallowing abaxially; bifurcate, with short posterior branch (Fig. 18.12, 19.7). LO with weakly curved posterior margin, represents 17% (16–18%) of glabellar length. Three pairs of lateral glabellar furrows. S1 bigeniculate, firmly impressed (Fig. 18.6); S2 convex, gently curved, shallower than S1; S3 shallowest, nearly transverse (Fig. 18.6), difficult to discern on some specimens. Palpebral area of fixigena broad (tr.), nearly flat, width equal to 71% (69–73%) of glabellar width at L2. Palpebral lobe slopes gently upward (Fig. 19.3); long, arcuate in outline, extending from midpoint of L1 to just beyond S2, length (exsag.) equal to 54% (47–60%; higher values in smaller cranidia). Palpebral furrow firmly impressed groove. Palpebral ridge extends obliquely inward and forward to reach axial furrow near S3. Anterior branches of facial sutures strongly divergent anteriorly, resulting in a forwardly expanding frontal area (tr.), before curving inward along anterior cranidial margin; posterior branches diverge along nearly straight paths. Posterior margin of postocular area curved backward in lateral view; slender (exsag.) posterolateral projection dips gently abaxially. Posterior border furrow clearly defined, nearly straight; posterior border expands (exsag.) abaxially. External surface mostly smooth but with scattered granules over crest of glabella. Well-developed caecal network on preglabellar field, which is also faintly pitted on some specimens; terrace ridges may be present on front edge of anterior border.

44Pygidium roughly semielliptical in outline, length (sag.) equal to 45% of maximum pygidial width opposite second axial ring; short articulating facet at anterior corner. Axis convex, occupies about 80% of pygidial length (sag.), with width at first axial ring equal to 25% of maximum pygidial width. Axis with three axial rings and terminal piece separated by nearly transverse ring furrows. Articulating half-ring semielliptical in outline, accounts for about 15% of axis length; articulating furrow transverse, well defined. Terminal piece represents about a quarter of axis length. Pleural field broad (tr.), almost flat near axis, but curves downward abaxially. Pleural furrows well defined at anterior but become progressively fainter toward rear. Interpleural furrows identifiable only anteriorly. Border furrow shallow, gently down-sloping border separated from pleural field in part by change in slope. Border widest at anterior, narrows toward rear of pygidium. Patches of exoskeleton on pleural field with fine granules; internal mold with scattered faint pits.

Etymology

From arquatus (Latin), “bent like a bow,” in reference to the curvature of the anterior border of the cranidium.

Remarks

Cranidia of “Eugonocare” arquatum from HC 202 are similar to “E.” angularum (Shaw and Clark in Clark and Shaw, Reference Clark and Shaw1968) from the Gorge Formation of Vermont in possessing a long preglabellar field that occupies about 25% of cranidial length (Figs. 18.3, 18.4, 19.7). However, the holotype and a similarly sized paratype of “E.” angularum have a weakly curved anterior border (Clark and Shaw, Reference Clark and Shaw1968, pl. 54, figs. 2, 5), whereas all specimens from HC 202 have a much more strongly curved border (Figs. 18.3, 18.4, 18.6, 18.7, 19.1, 19.7). The pygidia from HC 202 (Fig. 19.4–19.6) are similar to those suggested as possibly belonging to “E.” angularum by Clark and Shaw (Reference Clark and Shaw1968, p. 396, pl. 53, figs. 22–28). They are comparable in the length and segmentation of the axis, but the specimens from Vermont have a weak median deflection and arch of the posterior margin.

The long preglabellar field and strongly curved anterior border distinguish “E.” arquatum from “E.” tessellatum (Shergold, Reference Shergold1982, pl. 10, figs. 3, 4) and “E.” whitehousei (Henderson, Reference Henderson1976, pl. 49, figs. 16, 19) from western Queensland. The latter also has a relatively longer pygidium (Henderson, Reference Henderson1976, pl. 49, fig. 18) than “E.” arquatum. Among Laurentian species, the long pygidium, shorter preglabellar field, and smaller palpebral lobe of “E.” separatum (Palmer, Reference Palmer1962, pl. 5, figs. 8, 12, 13, 15, 16, 24, 26; Pratt, Reference Pratt1992, pl. 17, figs. 1–8) distinguish it from “E.” arquatum. “Eugonocare”? phillipi Chatterton and Gibb, Reference Chatterton and Gibb2016, from the McKay Group of British Columbia, approaches “E.” arquatum in the length of the preglabellar field but has a shorter (exsag.) palpebral lobe and a narrower (tr.) palpebral area of the fixigena (Chatterton and Gibb, Reference Chatterton and Gibb2016, pl. 24, fig. 1). The pygidium of “E.”? phillipi is known only from a ventral view of a compacted exoskeleton (Chatterton and Gibb, Reference Chatterton and Gibb2016, pl. 24, figs. 4, 5) but is apparently much shorter (exsag.) than the pygidium of “E.” arquatum (Fig. 19.4–19.6).

Family Pterocephaliidae Kobayashi, Reference Kobayashi1935

Subfamily Pterocephaliinae Kobayashi, Reference Kobayashi1935

Remarks

Palmer (Reference Palmer1965) divided family Pterocephaliidae into three subfamilies, Pterocephaliinae Kobayashi, Reference Kobayashi1935, Housiinae Hupé, Reference Hupé1955, and Aphelaspidinae Palmer, Reference Palmer1960. Species of Pterocephalinae and Housiinae possess median sutures, whereas species of Aphelaspidinae have rostral plates. Accordingly, we follow recent practice (Adrain, Reference Adrain2011; Hopkins, Reference Hopkins2011) of treating Aphelaspidinae as a separate family. Aphelaspididae and Pterocephaliidae were both assigned to order Olenida by Adrain (Reference Adrain2011), but the relationship between them, if any, has not yet been established in modern terms. The stratigraphical narrative proposed by Palmer (Reference Palmer1965, fig. 10) suggests that Aphelaspis is most closely related to species of Housiinae.

In proposing Pterocephalops, Rasetti (Reference Rasetti1944, p. 254) compared it with Pterocephalina Resser, Reference Resser1938, which was named for Dikellocephalus bilobatus Hall and Whitfield, Reference Hall and Whitfield1877. Palmer (Reference Palmer1956) treated D. bilobatus as a senior synonym of Dicellocephalus richmondensis Walcott, Reference Walcott1884, which is the type species of Litocephalus Resser, Reference Resser1937. As a result, Palmer (Reference Palmer1956) concluded that Pterocephalina was a junior synonym of Litocephalus. However, there is reason to doubt synonymy of P. bilobata and L. richmondensis. Pterocephalina bilobata is based on a single pygidium preserved in ventral orientation (Hall and Whitfield, Reference Hall and Whitfield1877, pl. 2, fig. 36; Palmer, Reference Palmer1956, pl. 73, fig. 2), whereas L. richmondensis is based on one cranidium (Walcott, Reference Walcott1884, pl. 10, fig. 7; Palmer, Reference Palmer1956, pl. 73, fig. 1). Palmer’s (Reference Palmer1956, p. 610) conclusions are based in part on a partly weathered, complete exoskeleton with “an imperfectly preserved and somewhat crushed cephalon” that he considered to be “certainly congeneric with L. bilobatus.” This specimen has a pygidium that is similar in outline to the holotype of P. bilobata, but it is difficult to make comparisons between the cephalon and the holotype of L. richmondensis.

Given the limitations of the respective type material of Pterocephalina and Litocephalus, Palmer (Reference Palmer1956) relied on sclerites from a different collection (USGS locality 1297 [CO]) to describe L. bilobata. The holotype of P. bilobata has a median embayment in the posterior margin, and Palmer (Reference Palmer1956, p. 608) noted that an embayment was also present in a pygidium from USGS locality 1297 (CO). However, these characters differ in detail, with a broad, rounded embayment in the holotype of P. bilobata and a narrower, roughly triangular embayment in the other figured pygidium (compare Palmer, Reference Palmer1956, pl. 73, figs. 2 and 5). Similarly, the figured cranidium from USGS locality 1297 (CO) (Palmer, Reference Palmer1956, pl. 73, fig. 4) has a narrower palpebral area of the fixigena and, consequently, a narrower (tr.) frontal area than the holotype of L. richmondensis (Palmer, Reference Palmer1956, pl. 73, fig. 1). Palmer (Reference Palmer1956, p. 610) was aware of these differences but stated that they were a consequence of a difference in size of these sclerites, and that “large cranidia … at USGS locality 1297 (CO) are essentially identical to the holotype of D. richmondensis.” Unfortunately, this has never been demonstrated because in subsequent work, Palmer (Reference Palmer1960, pl. 7, figs. 24–27; 1965, pl. 11, figs. 13–15) simply reillustrated the same specimens from USGS locality 1297 (CO) that he figured in 1956. From the published record, it is impossible to be sure that Palmer’s synonymy of P. bilobata and L. richmondensis is correct; nor can we be certain of the accuracy of his identification of sclerites from USGS locality 1297 (CO). Indeed, one could make a case for limiting Pterocephalina and Litocephalus to the holotypes of the respective type species.

Genus Pterocephalops Rasetti, Reference Rasetti1944

Type species

Pterocephalops acrophthalma Rasetti, Reference Rasetti1944, Lévis Formation, Middle Ridge, Quebec City, Quebec (by original designation).

Diagnosis

Frontal area divided into steeply downsloping preglabellar field and concave anterior border. Palpebral area of fixigena steeply upsloping, nearly reaching level of crest of glabella. Glabella parallel-sided, with lateral glabellar furrows barely expressed. Scattered tubercles on at least palpebral and posterior areas of fixigena. Librigena with broad (tr.), relatively flat genal spine that continues curvature of lateral margin without any outward deflection.

Remarks

Rasetti (Reference Rasetti1944, Reference Rasetti1961) left Pterocephalops (Figs. 20–22) unassigned at the family level, but Palmer (Reference Palmer1960, Reference Palmer1962) included the genus in Pterocephaliidae, although he did not place it in either of the subfamilies that he recognized at the time, Aphelaspidinae and Pterocephaliinae. The presence of tubercles in the anterior border furrow (Figs. 21.4, 22.3) indicates that Pterocephalops belongs in order Olenida, but other cranidial characters could be compatible with an assignment to Pterocephaliidae or Dokimocephalidae. Among Pterocephaliinae, the proportions of the frontal area invite comparison with species of Sigmocheilus Palmer, Reference Palmer1960 (Palmer, Reference Palmer1965, pl. 15, figs. 7, 13, 16), although they differ from Pterocephalops in having much longer (exsag.) palpebral lobes. Some species of Cernuolimbus Palmer, Reference Palmer1960 also have a similar division of the frontal area and are closer to Pterocephalops in the size of the palpebral lobes (Palmer, Reference Palmer1965, pl. 14, figs. 2, 4, 9). Moreover, pterocephaliines have concave borders, and this state was a synapomorphy (character 1, state 1) uniting the subfamily in some of Hopkins’ (Reference Hopkins2011, p. 1144, figs. 7.1, 8.1, 9.1) phylogenetic analyses. Pterocephalops has a distinctly concave border (Figs. 20.3, 21.3, 21.4, 21.5).

Figure 20.

Cranidia of Pterocephalops acrophthalma Rasetti, Reference Rasetti1944 boulder HC 202, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1–3) GSC 144599: (1) dorsal view; (2) anterior view; (3) lateral view. (4–6) GSC 144600: (4) dorsal view; (5) anterior view; (6) lateral view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 20. Long description

Six photographs of Pterocephalops acrophthalma cranidia. White scale bars represent 1 mm.

Photographs 1–3 show dorsal, anterior and lateral views, respectively, of a specimen with the GSC catalogue number 144599. The dorsal view (1) features a parallel-sided glabella, long anterior border and tubercles on the external surface, some of which are paired. The anterior view (3) demonstrates that the preglabellar field slopes steeply forward and that the anterior border is concave.

.

Photographs 4–6 show anterior, lateral and dorsal views, respectively, of a specimen with the GSC catalogue number 144600. All three views demonstrate that tubercles extend onto the external surface of the anterior border in some specimens.

Figure 21.

Cranidia of Pterocephalops cf. P. tuberculineata Clark in Clark and Shaw, Reference Clark and Shaw1968, boulder HC 166, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1–3) GSC 144603: (1) dorsal view; (2) anterior view; (3) lateral view. (4, 5) GSC 144604: (4) dorsal view; (5) lateral view. (6, 7) GSC 144605: (6) dorsal view; (7) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 21. Long description

Seven photographs of cranidia of Pterocephalops cf. P. tuberculineata. White scale bars represent 1 mm.

Photographs 1–3 show dorsal, anterior and lateral views, respectively, of a specimen with the GSC catalogue number 144603. The dorsal view (1) shows the nearly parallel-sided glabella and the long frontal area. The anterior view (2) indicates that the fixed cheeks slope upward, and the lateral view (3) shows the forward slope of the frontal area.

Photographs 4–6 show dorsal, anterior and lateral views of a specimen with the GSC catalogue number 144604. Although damaged, it confirms the major features of the anatomy visible in the better preserved specimen (1–3).

Figure 22.

Pterocephalops cf. P. tuberculineata Clark in Clark and Shaw, Reference Clark and Shaw1968, boulder HC 166, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1, 2) Librigena. (3–6) Cranidia. (1, 2) GSC 144601: (1) dorsal view; (2) lateral view. (3) GSC 144602, dorsal view. (4–6) GSC 143201: (4) dorsal view; (5) lateral view; (6) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 22. Long description

Six photographs of cranidia and a librigena of Pterocephalops cf. P. tuberculineata. White scale bars represent 1 mm.

Photographs 1, 2, are dorsal and lateral view of a librigena with the GSC catalogue number 144601. Both views show a long curved genal spine.

Photograph 3 is a dorsal view of a cranidium with the GSC catalogue number 144602. The shell is mostly missing and the internal mold shows the characteristic tubercles in the anterior border furrow.

* Photographs 4–6 are dorsal, lateral and anterior views, respectively, of a small cranidium with the GSC catalogue number 143201. The frontal area is proportionately shorter than in larger specimens.

The frontal area of the type species of the dokimocephalid Iddingsia, I. similis (Walcott, Reference Walcott1884), is close to the configuration in Pterocephalops, differing primarily in having a less steeply inclined preglabellar field and a down-sloping, rather than concave, anterior border (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 15A–D, L–P). The presence of scattered fine tubercles on the external surface is shared with a number of dokimocephalids (Fig. 10.1–10.3, 10.6–10.8; Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, figs. 4A–C, 12F, 12G, 23G, 27A–J), whereas pterocephaliids are typically smooth or finely pitted (Palmer, Reference Palmer1965, p. 57). The phylogenetic analysis of Dokimocephalidae by Westrop et al. (Reference Westrop, Waskiewicz Poole and Adrain2010, figs. 2, 3) was limited to a subset of species assigned to Dokimocephalus and closely related genera such as Iddingsia. This group of species was monophyletic and was united by a posterior position of the palpebral lobe (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, figs. 7C, 15L, 19J, 23A, 29B), a narrow genal spine curved outward and backward (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, figs. 14D–F, 20A, B), and an inflated border at the intersection with the base of the spine (Westrop et al., Reference Westrop, Waskiewicz Poole and Adrain2010, fig. 14D–F). The palpebral lobe is more anteriorly positioned in Pterocephalops, but this resembles the condition in genera traditionally assigned to Dokimocephalidae that were not included in the analysis by Westrop et al. (Reference Westrop, Waskiewicz Poole and Adrain2010; Figs. 9.1, 14.1, 14.4). If assigned correctly, the librigena of Pterocephalops (Fig. 22.1, 22.2) has a broad, relatively flat spine that continues the curvature of the lateral margin and carries a weakly convex extension of the posterior border at least anteriorly. In these respects, it resembles the librigena of pterocephaliines such as Cernuolimbus (Palmer, Reference Palmer1965, pl. 14, fig. 18) rather than those of Dokimocephalus and related genera.

Although some characters are ambiguous, the balance of evidence currently supports an assignment of Pterocephalops to subfamily Pterocephaliinae. Discovery of the pygidium may provide further resolution of the relationships of the genus.

Pterocephalops acrophthalma Rasetti, Reference Rasetti1944

Figures 9.3–9.5, 20

Reference Rasetti1944 Pterocephalops acrophthalma Rasetti, p. 254, pl. 39, figs. 35–38.

Reference Rasetti1961 Pterocephalops acrophthalma; Rasetti, p. 117, pl. 24, figs. 13–16.

Types

We designate a cranidium (GSC 144568 [LU 1163a]; Rasetti, Reference Rasetti1944, pl. 39, figs. 35, 37; Fig. 9.3) from Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec, as the lectotype. The other cranidium illustrated by Rasetti (GSC 144569 [LU 1163b]; Rasetti, Reference Rasetti1944, pl. 39, figs 36, 38; Fig. 9.4, 9.5) is a paralectotype.

Other material

Two cranidia (GSC 144599, Fig. 20.1–20.3; GSC 144600, Fig. 20.4–20.6) from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland.

Diagnosis

Tubercles absent from anterior border furrow on internal mold. Frontal area occupies no more than 30% of cranidial length.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland; Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna. Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec (Rasetti, Reference Rasetti1944). Rocky Springs Station Member, Frederick Limestone, near Frederick, Maryland (Rasetti, Reference Rasetti1961).

Remarks

The type cranidia of Pterocephalops acrophthalma Rasetti, Reference Rasetti1944 (Fig. 9.3–9.5) have a few small tubercles on the fixigenae (arrows on Fig. 9.4), and the frontal area is no more than 30% of cranidial length. Cranidia from HC 202 have a frontal area with similar proportions but vary more in the development of tubercles. The smaller specimen (Fig. 20.1–20.3) has a few paired tubercles on the posterior and palpebral areas and on the glabellar lobes; an irregular row of tubercles is developed in front of the glabella, but none is present on the anterior border. The large cranidium (Fig. 20.4–20.6) has more tubercles on the glabella, preocular and preglabellar field, and they extend onto the anterior border. Rasetti (Reference Rasetti1961, p. 117) reported that some topotypes of P. acrophthalma had “fairly large, scattered tubercles on the anterior border and on the posterior portion of the preglabellar field.”

Clark and Shaw (Reference Clark and Shaw1968, p. 386) mentioned that, although they were not included in the diagnosis, “the rather numerous tubercles as contrasted with the very few visible in Rasetti’s illustrations” were a minor but consistent difference separating P. tuberculineata Clark in Clark and Shaw, Reference Clark and Shaw1968 from P. acrophthalma. However, the variation in the expression of tubercles in the cranidia from HC 202 suggests that their utility in separating species may be overestimated. An exception may be the tubercles developed in the anterior border furrow of cranidia from HC 166 (Fig. 21.4, 21.6, 21.7), arranged in three shallow depressions. These are not present in cranidia from HC 202. Cranidia from HC 166 resemble the holotype (Clark and Shaw, Reference Clark and Shaw1968, pl. 54, fig. 15) of P. tuberculineata in having a longer frontal area that is equal to about 35% of cranidial length. We assign the cranidia from HC 202 to P. acrophthalma, whereas the specimens from HC 166 are placed in open nomenclature below.

Pterocephalops cf. P. tuberculineata Clark in Clark and Shaw, Reference Clark and Shaw1968

Figures 21, 22

cf. Reference Clark and Shaw1968 Pterocephalops tuberculineata Clark in Clark and Shaw, p. 385, pl. 54, figs. 11–15.

Reference Westrop and Engel2023 Pterocephalops cf. P. tuberculineata Clark in Clark and Shaw; Westrop and Engel, fig. 3c.

Material and occurrence

Five cranidia (GSC 144603, Fig. 21.1–21.3; GSC 144604, Fig. 21.4, 21.5; GSC 144605, Fig. 21.6, 21.7; GSC 144602, Fig. 22.3; GSC 143201, Fig. 22.4–22.6) and one librigena (GSC 144601, Fig. 22.1, 22.2) from the Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

The longer frontal area of larger cranidia (equal to 35% of cranidial length; Figs. 21.1–21.6, 22.3) from HC 202 resembles P. tuberculineata, although it is relatively shorter in the smallest specimen (Fig. 22.4–22.6; equal to about 25% of cranidial length). They have better-defined, albeit still weak, S1 and, on some specimens, S2 lateral furrows than in P. acrophthalma, which Clark and Shaw (Reference Clark and Shaw1968, p. 386) considered to be a diagnostic character. The fact remains that P. tuberculineata is based on only two poorly illustrated cranidia (Clark and Shaw, Reference Clark and Shaw1968, pl. 54, figs. 11–15). The published photographs are not good enough to establish the presence of the tubercles in the border furrow that are evident in specimens from HC 202, and they are not mentioned in Clark and Shaw’s (Reference Clark and Shaw1968) description. Consequently, our material is placed in open nomenclature.

An associated librigena (Fig. 22.1, 22.2) has a long, relatively wide (tr.) genal spine. The specimen is complete enough to show that the spine continues the curvature of the lateral margin without any outward deflection. The lateral border is broad and nearly flat and is separated from the convex librigenal field by a change of slope; an incised border furrow is absent. The posterior border is defined by a gently impressed border furrow. It extends onto the genal spine but becomes reduced in convexity and cannot be identified posteriorly. As noted above, it is similar to the librigena of the pterocephaline Cernuolimbus.

Order Uncertain

Superfamily Dikelocephaloidea Miller, Reference Miller1889

Family Dikelocephalidae Miller, Reference Miller1889

Genus Prosaukia Ulrich and Resser, Reference Ulrich and Resser1933

Type species

Dikelocephalus misa Hall, Reference Hall1863 from the Lone Rock Formation of Wisconsin (by original designation).

Prosaukia? aff. P. hartti (Walcott, Reference Walcott1879)

Figure 17.7–17.9

aff. Reference Walcott1879 Conocephalites hartti Walcott, p. 130

aff. Reference Ludvigsen and Westrop1983 Prosaukia hartti (Walcott); Ludvigsen and Westrop, p. 30, pl. 10, figs. 1–8, pl. 11, figs. 1–13, pl. 12, figs. 1–7, text-fig. 6 (see for complete synonymy).

Material and occurrence

A cranidium (GSC 144575, Fig. 17.7–17.9) from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

A single cranidium from HC 202 shares S1 furrows that are connected across the glabella with Glyptometopsis? marginata Rasetti, Reference Rasetti1961 from the Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec (Rasetti, Reference Rasetti1961, pl. 25, figs. 12–15). The latter differs in having finely granulose sculpture (Rasetti, Reference Rasetti1961, p. 114), narrower palpebral area of the fixigena, and a preglabellar field that Rasetti (Reference Rasetti1961, p. 114) described as “almost vanishing medially.” The documentation of G.? marginata is insufficient to establish a relationship with our cranidium.

In describing their new genus, Imlerella, Loch and Taylor (Reference Loch and Taylor2004) extended the stratigraphical range of family Ptychaspididae Raymond, Reference Raymond1924 from the Sunwaptan down into the Steptoean (Elvinia Zone). The cranidium from HC 202 may record a similar range extension for the related family Dikelocephalidae. The S1 lateral furrows are connected across a convex, gently tapered, anteriorly rounded glabella that stands well above the palpebral area of the fixigena. The frontal area is divided into a short preglabellar field and longer, arcuate anterior border. Sculpture is in the form of coarse, irregular granules to fine tubercles, augmented with pits on the preglabellar and preocular fields. In all of these characters, the cranidium resembles small cranidia of Prosaukia hartti (Walcott, Reference Walcott1879) from the Hoyt Formation of New York (Ludvigsen and Westrop, Reference Ludvigsen and Westrop1983, pl. 11, figs. 4, 6). The specimens of P. hartti have much longer (exsag.) palpebral lobes, although they become reduced somewhat in relative size during holaspid ontogeny (Ludvigsen and Westrop, Reference Ludvigsen and Westrop1983, fig. 6), and S2 and S3 furrows are more firmly impressed. S2 in the cranidium from HC 202 is shallow and defined mostly by the absence of sculpture, whereas S3 lacks incision and is defined entirely by the absence of sculpture.

Although Prosaukia has relatively long palpebral lobes, palpebral lobes that are closer in size to those of the cranidium from HC 202 are present in some other dikelocephalid taxa. For example, some species of Eosaukia Lu, Reference Lu1954 have palpebral lobes that are roughly equal to the length of L2 (Shergold, Reference Shergold1991, pl. 5, figs. 10–13; Lee and Choi, Reference Lee and Choi2011, figs. 3.4, 7.1–7.10; Wernette et al., Reference Wernette, Hughes, Myrow and Sardsud2023, fig. 46A–AF). Caznaia Shergold, Reference Shergold1975 is also characterized by a relatively small palpebral lobe (Shergold, Reference Shergold1975, pl. 25, figs. 1, 6), as are Anderssonella beauchampi Shergold, Reference Shergold1975 (Shergold, Reference Shergold1975, pl. 20, fig. 4) and Diemanosaukia miserabilis Jago and Corbett, Reference Jago and Corbett1990 (Jago and Corbett, Reference Jago and Corbett1990, fig. 3C, J).

We conclude that a case can be made to interpret the cranidium as the oldest dikelocephalid in Laurentia, and discovery of the pygidium would be decisive. It is at minimum a new species, but for the present, we assign it questionably to Prosaukia and place it in open nomenclature.

Family Lonchocephalidae Hupé, Reference Hupé1953

Genus Quebecaspis Rasetti, Reference Rasetti1944

Type species

Quebecaspis breviceps Rasetti, Reference Rasetti1944 from boulder 51, Lévis Formation, Middle Ridge, Lévis, Quebec (by original designation).

Diagnosis

Frontal area very short with preglabellar field barely developed or absent. S1 glabellar furrow geniculate. Palpebral lobe long (exsag.), centered opposite anterior tip of S1 or L2.

Remarks

The affinities of Quebecaspis are far from certain, but Rasetti (Reference Rasetti1944, p. 254) compared it with Lonchocephalus Owen, Reference Owen1852. Both he (Rasetti, Reference Rasetti1961) and Clark and Shaw (Reference Clark and Shaw1968) placed the genus in Lonchocephalidae Hupé, Reference Hupé1953, but this family needs revision, and monophyly has yet to be demonstrated.

With guidance from the diagnoses by Rasetti (Reference Rasetti1944, Reference Rasetti and Moore1959) and commentary by Palmer (Reference Palmer1968, p. 94), we find a key character uniting species of Quebecaspis is a very short frontal area with a preglabellar field that is at best a mere vestige. Most species lack a preglabellar field entirely (Figs. 23, 24). Rasetti (Reference Rasetti1954, pl. 62, figs. 1–12) illustrated the cranidial ontogeny of the lonchocephalid Welleraspis Kobayashi, Reference Kobayashi1935 (Hu, Reference Hu1964, pl. 1, figs. 1–11, 19–38). Late meraspids and early holaspids have a very short frontal area in which the preglabellar field is absent or exceedingly short (Rasetti, Reference Rasetti1954, pl. 62, figs. 8, 9; Hu, Reference Hu1964, pl. 1, figs. 32, 33); the preglabellar field lengthens during the holaspid ontogeny (Rasetti, Reference Rasetti1954, pl. 62, figs. 10–12). The absence of a preglabellar field in Quebecaspis could simply record retention of what is an early ontogenetic morphology in other lonchocephalids well into the holaspis stage.

Figure 23.

Cranidia of Quebecaspis from the Shallow Bay Formation, western Newfoundland. (1–5, 10–12) Quebecaspis conifrons Rasetti, Reference Rasetti1961. (1–4) From boulder HC 202, Hickey Cove area. (5, 10–12) From boulder CH 57, Cow Head Peninsula. (1–3) GSC 143203: (1) dorsal view; (2) lateral view; (3) anterior view. (4) GSC 144609, dorsal view. (5) GSC 144610, dorsal view. (10–12) GSC 144611: (10) dorsal view; (11) lateral view; (12) anterior view. (6) Quebecaspis cf. Q. conifrons Rasetti, Reference Rasetti1961, GSC 144612, dorsal view, from boulder HC 202, Hickey Cove area. (7–9, 13) Quebecaspis aff. Q. conifrons Rasetti, Reference Rasetti1961. (7–9) From boulder CH 57, Cow Head Peninsula. (13) From boulder HC 202, Hickey Cove. (7–9) GSC 144613: (7) anterior view; (8) lateral view; (9) dorsal view. (13) GSC 144614, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 23. Long description

Thirteen photographs of cranidia of species of Quebecaspis. White scale bars represent 1 mm.

Photographs 1-3 show dorsal, lateral and anterior views of a large specimen of Quebecaspis conifrons with the GSC catalogue number 143203. The dorsal view (1) emphasizes the prominent anteriorly-rounded glabella and very narrow fixigenae. The lateral (2) and anterior (3) views demonstrate the strong elevation of the glabella above the fixigena.

*Photograph 4 shows a dorsal view of a specimen of Quebecaspis conifrons, with the GSC catalogue number 144609, similar in morphology to the larger specimen (1–3).

Photograph 5 shows a specimen with the GSC catalogue number 144610 in dorsal view, with a far less rounded and tapered glabella than larger cranidia.

Photograph 6 shows a dorsal view of a specimen of Quebecaspis cf. Q. conifrons with the GSC catalogue number 144612. Compared to similarly-sized cranidia of Q. conifrons (4), it has a far less rounded and tapered glabella.

Photographs 7-9 show anterior, lateral and dorsal views, respectively, of a specimen of Quebecaspis aff. Q. conifrons with the GSC catalogue number 144613. All three views display the relatively wide fixigena and short palpebral lobe that characterize this species.

Photographs 10–12 depict dorsal, lateral and anterior views of small specimen of Quebecaspis conifrons with the GSC catalogue number 144611. It differs from larger specimens in having a less rounded glabella.

Photograph 13 shows a dorsal view of a specimen of Quebecaspis aff.Q. conifrons with the GSC catalogue number 144614, featuring the characteristic wide fixigena.

Figure 24.

Cranidia of Quebecaspis cf. Q. marylandica Rasetti, Reference Rasetti1961, boulder HC 202, Shallow Bay Formation, Hickey Cove area, western Newfoundland. (1–3) GSC 144606: (1) dorsal view; (2) lateral view; (3) anterior view. (4–6) GSC 144607: (4) lateral view; (5) dorsal view; (6) anterior view. (7–9) GSC 143202: (7) anterior view; (8) lateral view; (9) dorsal view. (10) GSC 144608, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 24. Long description

Ten photographs of cranidia of Quebecaspis cf. Q. marylandica. White scale bars represent 1 mm.

Photograps 1–3 show dorsal, lateral and anterior views, respectively, of a large specimen with the GSC catalogue number 144606. The dorsal view (1) feature a trapezoidal glabellaand a large palpebral lobe. The lateral (2) and anterior (3) views show that the glabella stands well above the level of the fixigena.

Photographs 4–6 show lateral, dorsal and anterior views of a specimen with the GSC catalogue number 144607. It is similar in morphology to the largest specimen (1–3), but is better preserved.

Photographs 7–9 show anterior, lateral and dorsal views, respectively of a small specimen with the GSC catalogue number143202. It preserves the base of an occipital spine and also shows the geniculate shape of the S1 glabellar furrow.

Photograph 10 shows a dorsal view of a small specimen with the GSC catalogue number 144608 It resembles the other small specimen in the outline of the glabella, but lacks an occipital spine l.

Both Rasetti (Reference Rasetti1954) and Palmer (Reference Palmer1968) considered a tapered, subtrapezoidal glabella to be diagnostic, but species from CH 57 have glabellae that are parallel-sided (Fig. 25.1) or very nearly so (Fig. 25.2–25.6). Similarly, there are species that lack an occipital spine (Fig. 23.1–23.13). Where visible, S1 furrows are geniculate (Fig. 24.1, 24.5, 24.9), although as noted, this configuration is shared with other lonchocephalid genera and catillicephalid genera, such as Welleraspis (Lochman, Reference Lochman1968, pl. 149, fig. 2), Pemphigaspis (Pratt, Reference Pratt1992, pl. 27, fig. 19), and Catillicephala Raymond, Reference Raymond1937 (Westrop and Dengler, Reference Westrop and Dengler2022, figs. 1C₁, 2C₂, C₃). The palpebral lobe is relatively long (exsag.) and centered opposite the anterior tip of S1 or L2. These characters are incorporated into a revised diagnosis that is descriptive in nature given that the affinities of Quebecaspis are unclear.

Figure 25.

Cranidia of Quebecaspis from the Shallow Bay Formation, western Newfoundland. All from boulder CH 57. (1) Quebecaspis sp. 1. GSC 144615, dorsal view. (2–6) Quebecaspis sp. 2. (2, 3) GSC 144616: (2) dorsal view; (3) anterior view. (4–6) GSC 144617: (4) lateral view; (5) dorsal view; (6) anterior view. (7, 8) Quebecaspis sp. 3, GSC 144618: (7) dorsal view; (8) anterior view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 25. Long description

Eight photographs of cranidia of species of Quebecaspis. White scale bars represent 1 mm.

Photograph 1 shows a dorsal view of a unique specimens that represents a new species, with the GSC catalogue number 144615. It is characterized by a rectangular, unfurrowed glabella and a well developed occipital spine.

Photographs 2–6 show Quebecaspis sp. 2.

Photographs 2 and 3 are dorsal and anterior views of a specimen with the GSC catalogue number 144616. Both views show the characteristic coarse granules on the fixigenae and an unfurrowed, nearly rectangular glabella.

Photographs 4–6 show lateral, dorsal and anterior views of a specimen with the GSC catalogue number 144617. It is smaller than the other specimen (2, 3) and has a shorter anterior border.

Photographs 7 and 8 show dorsal and anterior views of a specimen of Quebecaspis species 3 Both views show that this species differs from Q.sp. 1 in having a well-furrowed trapezoidal glabella and in lacking coarse granules on the fixigenae.

Quebecaspis breviceps Rasetti, Reference Rasetti1944

Figure 9.6

Reference Rasetti1944 Quebecaspis breviceps Rasetti, p. 254, pl. 39, figs. 44, 45.

Types

We designate a cranidium (GSC 144570; LU 1163a; Rasetti, Reference Rasetti1944, fig. 44; Fig. 9.6) from Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec, as the lectotype.

Diagnosis

Glabella distinctly tapered, trapezoidal in outline. Very short preglabellar field with clear separation of preglabellar and anterior border furrows. Internal mold of fixigena punctate.

Occurrence

Lévis Formation, boulder 51, Middle Ridge, Quebec City, Quebec, Quebecaspis conifrons Fauna.

Remarks

Quebecaspis breviceps is known from only two figured cranidia, the most complete of which is reillustrated (Fig. 9.6) and selected as the lectotype. The glabella is distinctly tapered, particularly in the other, larger specimen illustrated by Rasetti (Reference Rasetti1944, pl. 39, fig. 45) and is trapezoidal in outline. Although Rasetti (Reference Rasetti1944, p. 254) claimed that the preglabellar field was absent, the lectotype preserves the exoskeleton in this region, and there is a clear separation between the anterior border and the anterior end of the glabella. As the species is from a single boulder in the Lévis Formation, there is little prospect of additional material becoming available, and we recommend that the name be restricted to the types.

Quebecaspis conifrons Rasetti, Reference Rasetti1961

Figure 23.1–23.5, 23.10–23.12

Reference Rasetti1961 Quebecaspis conifrons Rasetti, p. 117, pl. 24, figs. 23–25.

Reference Palmer1968 Quebecaspis conifrons? Rasetti; Palmer, p. 95, pl. 9, figs. 8–10.

Reference Westrop and Engel2023 Quebecaspis conifrons Rasetti; Westrop and Engel, p. 137, fig. 3e.

Types

Rasetti’s types are three cranidia housed at the National Museum of Natural History, Washington, DC (USNM). The holotype (USNM 143092; Rasetti, Reference Rasetti1961, pl. 24, fig. 24) and two paratypes (USNM 143091, USNM 143093; Rasetti, Reference Rasetti1961, pl. 24, figs. 23, 25) are from the Rocky Springs Station Member, Frederick Limestone, near Frederick, Maryland (localities ccm/3 and ccm/4; Rasetti, Reference Rasetti1961, p. 107).

Other material

Downes Point Member, Shallow Bay Formation. Two cranidia (GSC 144610, Fig. 23.5; GSC 144611, Fig. 23.10–23.12) from boulder CH 57, Cow Head Peninsula. Two cranidia (GSC 143203, Fig. 23.1–23.3; GSC 144609, Fig. 23.4) from boulder HC 202, Hickey Cove area, western Newfoundland.

Diagnosis

Anterior border furrow merges with preglabellar furrow in all but largest specimen, which has extremely short preglabellar field; posterior side of anterior border deflected slightly forward by glabella where preglabellar field absent. LO without occipital spine. Lateral glabellar furrows barely incised. S1 furrow oblique near axial furrow, with gentle backward curvature near adaxial tip. Very narrow (tr.) palpebral area of fixigena equal to 23% (21–25%) of glabellar width. Palpebral lobe extends from anterior end of L1 to S3. External surface of cranidium with granulose sculpture.

Occurrence

Downes Point Member, Shallow Bay Formation, Cow Head Peninsula and Hickey Cove area, western Newfoundland; Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna. Rocky Springs Station Member, Frederick Limestone, near Frederick, Maryland (Rasetti, Reference Rasetti1961). Jones Ridge Limestone, Hi-Yu area, east-central Alaska (Palmer, Reference Palmer1968).

Description

Cranidium strongly arched in lateral and anterior views (Fig. 23.2, 23.3), with length (sag.) equal to 83% (80–85%) of width (tr.) across palpebral lobes. Frontal area lacks preglabellar field in all but largest specimen (Fig. 25.1), with anterior border furrow merging with preglabellar furrow. Anterior border convex, with posterior side deflected slightly forward by glabella where preglabellar field absent (Fig. 23.5, 23.10). Glabella dominates cranidium, occupying 89% of length (sag.) and 68% (66–70%) of width across palpebral lobes and accounting for about half of cranidial height in lateral view (Fig. 23.2); anteriorly rounded, tapers strongly forward in largest specimens (Fig. 23.1, 23.4), width opposite anterior tip of palpebral lobe equal to 70% (67–74%) of width at abaxial end of S1, but less so in smaller specimens (Fig. 23.10–23.12), in which the same dimensions yield a proportion of about 80%. SO nearly transverse medially but curved forward abaxially; well incised on external surface but longer (sag., exsag.) and deeper on internal mold; LO occupies 15% of glabellar length, lacks occipital spine. All specimens have faint S1, oblique near axial furrow, with gentle backward curvature near adaxial tip (Fig 23.1, 23.2); oblique S2 on most small specimens, S3 may also be expressed (Fig. 23.4). Maximum length of L1 accounts for 21% (20–22%) of glabellar length; where visible, L2 similar in maximum length. Palpebral area of fixigena very narrow, equal to 23% (21–25%) of glabellar width at S1. Arcuate palpebral lobe nearly flat (Fig. 23.3) and long (exsag.), extending from anterior end of L1 to S3 and equal to 40% (37–42%) of glabellar length (sag.). Anterior branches of facial sutures converge forward before swinging abruptly inward along anterior margin; posterior branches abruptly divergent before turning backward, becoming nearly parallel. Posterior area dips gently backward; posterolateral projection flexed steeply downward, maximum length (exsag.) equal to 20% (19–21%) of cranidial length (sag.). Posterior border furrow evenly incised groove; convex posterior border expands (exsag.) abaxially. External surface of cranidium with granulose sculpture (Fig. 23.4).

Remarks

Rasetti’s (Reference Rasetti1961) original description of Quebecaspis conifrons was illustrated with three incomplete cranidia from the Rocky Springs Station Member, Frederick Limestone, near Frederick, Maryland (Rasetti, Reference Rasetti1961, pl. 24, figs. 23–25). Two cranidia from CH 57 and HC 202 (Fig. 23.1–23.4) are very similar to Rasetti’s types, with a strongly tapered glabella that is well rounded anteriorly. Two smaller cranidia from CH 57 (Fig. 23.5, 23.10–23.12) have less-tapered, albeit still well-rounded, glabellae but share several character states with the larger specimens. These include a very narrow (tr.) palpebral area, an elongate palpebral lobe that extends from the anterior end of L1 to S3, and S1 furrows that are more oblique than geniculate; the posterior side of anterior border is deflected slightly forward by glabella (compare Fig. 23.1 with Fig. 23.5, 23.10). We interpret these smaller specimens as earlier ontogenetic morphotypes of Q. conifrons.

One cranidium from HC 202 (Fig. 23.6) is problematic. The glabella is weakly tapered and less rounded, and yet this sclerite is similar in size to a specimen from the same collection whose strongly tapered glabella is well rounded anteriorly and conforms to the diagnosis of Q. conifrons (Fig. 23.4). As such, this variation cannot be viewed as a simple ontogenetic difference, and the specimen is placed in open nomenclature (Quebecaspis cf. Q. conifrons). It is similar in glabellar outline to Q. hemispherica Clark in Clark and Shaw, Reference Clark and Shaw1968 from the Gorge Formation of Vermont (Clark and Shaw, pl. 55, figs. 1–4) but differs in having a longer (exsag.) palpebral lobe and faint, rather than well-incised, lateral glabellar furrows.

Palmer (Reference Palmer1968, pl. 9, figs. 8–10) illustrated cranidia from the Jones Ridge Limestone, Alaska, some of which possess a distinct preglabellar field but are otherwise similar to Rasetti’s types. However, at least some specimens from Newfoundland also possess a very short preglabellar field (Fig. 23.2), and we assign the cranidia from Alaska to Q. conifrons without question.

Quebecaspis cf. Q. marylandica Rasetti, Reference Rasetti1961

Figure 24

cf. Reference Rasetti1961 Quebecaspis marylandica Rasetti, p. 117, pl. 24, figs. 17–22

Reference Westrop and Engel2023 Quebecaspis cf. Q. marylandica Rasetti; Westrop and Engel, p. 137, fig. 3d.

Material and occurrence

Four cranidia (GSC 144606, Fig. 24.1–24.3; GSC144607, Fig. 24.4–24.6; GSC 143202, Fig. 24.7–24.9; GSC 144608; Fig. 24.10) from the Downes Point Member, Shallow Bay Formation, boulder HC 202, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

Quebecaspis marylandica Rasetti, Reference Rasetti1961 from the Rocky Springs Station Member, Frederick Limestone near Frederick, Maryland, is poorly documented with small photographs (Rasetti, Reference Rasetti1961, pl. 24, figs. 17–22) and is difficult to evaluate fully. Cranidia from HC 202 (Fig. 24.1–24.10) are broadly similar but differ in some details. Both sets of cranidia lack a preglabellar field and have gently tapered glabellae, and at least some specimens have a small occipital spine (Fig. 24.9). S1 furrows are geniculate in both species. The anterior border of Q. marylandica tends to be more strongly curved, although some specimens approach cranidia from HC 202 (compare Rasetti, Reference Rasetti1961, pl. 24, fig. 20 and Fig. 24.10). There is a gentle arch in anterior view (Fig. 24.3). The palpebral area of the fixigena of Q. marylandica is narrower than in the specimens from HC 202, although measurements from Rasetti’s (Reference Rasetti1961) photographs show that there is some overlap in the ranges; width of the palpebral area is 34% (31–35%) of glabellar width at SO for the types and 40% (32–45%) for specimens from HC 202. Sculpture is not evident on the photographs of the types from Maryland, but Rasetti (Reference Rasetti1961, p. 117) described the external surface as “apparently smooth.” Cranidia from HC 202 have an external surface with granules present on LO (Fig. 24.5); faint granules may also be present on fixigena of smaller specimens (Fig. 24.9). It is possible that cranidia from HC 202 represent a distinct species, but given the small sample sizes available from both regions, we use open nomenclature.

Although introduced as a subspecies of Q. marylandica, we prefer to treat Q. tuberculata Clark in Clark and Shaw, Reference Clark and Shaw1968 from the Gorge Formation of Vermont as a distinct species. It has a more robust occipital spine than Quebecaspis cf. Q. marylandica (Clark and Shaw, Reference Clark and Shaw1968, pl. 56, figs. 7, 14), although the surface sculpture is apparently similar. Also from the Gorge Formation, Q. hemispherica has an anteriorly rounded glabella, deeply incised S1 furrows, and an anterior border that forms a narrow rim (Clark and Shaw, Reference Clark and Shaw1968, pl. 55, figs. 1–4, 14–16).

Quebecaspis aff. Q. conifrons Rasetti, Reference Rasetti1961

Figure 23.7–23.9, 23.13

aff. Reference Rasetti1961 Quebecaspis conifrons Rasetti, p. 117, pl. 24, figs. 23–25.

aff. Reference Palmer1968 Quebecaspis conifrons? Rasetti; Palmer, p. 95, pl. 9, figs. 8–10.

aff. Reference Westrop and Engel2023 Quebecaspis conifrons Rasetti; Westrop and Engel, fig. 3e.

Material and occurrence

Downes Point Member, Shallow Bay Formation. One cranidium (GSC 144613, Fig. 23.7–23.9) from boulder CH 57, Cow Head Peninsula. One cranidium (GSC 144614, Fig. 23.13) from boulder HC 202, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

Two cranidia (Fig. 23.7–23.9, 23.13) differ from associated specimens of Q. conifrons in CH 57 and HC 202 (Fig. 23.1–23.5, 23.10–23.12) in having a wider (tr.) palpebral area of the fixigena and a shorter palpebral lobe whose posterior end lies in front of S1. Glabellar outline also separates these specimens from Q. conifrons. The glabella of the larger specimen (Fig. 23.7–23.9) is gently tapered and rounded anteriorly, but it is nearly rectangular in the smaller cranidium (Fig. 23.13). Quebecaspis cf. Q. conifrons from HC 202 (Fig. 23.6) is closer to both specimens in glabellar outline but has a narrower palpebral area and longer (exsag.) palpebral lobe that is more like Q. conifrons.

Glabellar outline resembles Q. hemispherica, which differs from Quebecaspis aff. Q. conifrons in having a much shorter anterior border and deep S1 and S2 furrows (Clark and Shaw, Reference Clark and Shaw1968, pl. 55, figs. 1–4, 14–16).

Quebecaspis sp. 1

Figure 25.1

Material and occurrence

A cranidium (GSC 144615, Fig. 25.1) from the Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

A unique cranidium from CH 57 almost certainly represents a new species. It possesses a distinctive, rectangular glabella that lacks lateral furrows and has a short, triangular occipital spine. The palpebral area of the fixigena is very wide and is equal to about half of glabellar length at SO. The large palpebral lobe is equal to slightly less than half of preoccipital glabellar length.

Quebecaspis sp. 2

Figure 25.2–25.6

Material and occurrence

Two cranidia (GSC 144616, Fig. 25.2, 25.3; GSC 144617, Fig. 25.4–25.6) from the Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

Two cranidia from CH 57 (Fig. 25.2–25.6) have scattered fine tubercles on the fixigena and, to a lesser extent, on the posterior third of the glabella. The glabella is nearly rectangular, and S1 furrows are at best barely perceptible. They differ from Quebecaspis sp. 1 in having a narrower palpebral area of the fixigena and in lacking an occipital spine.

Quebecaspis sp. 3

Figure 25.7, 25.8

Material and occurrence

A cranidium (GSC 144618, Fig. 25.7, 25.8) from the Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

A single cranidium from CH 57 is similar to Quebecaspis cf. Q. marylandica (Figs. 21.1–24.10) from HC 202 in glabellar outline, but it has a relatively longer anterior border that is not arched in anterior view.

Family Uncertain

Genus Bathyholcus Rasetti, Reference Rasetti1961

Type species

Bathyholcus gaspensis Rasetti, Reference Rasetti1961 from the lower Grosse Roches Formation, Grosses Roches, Matane County, western Gaspé peninsula, Quebec (by original designation).

Diagnosis

Glabella of low convexity, slightly tapered and weakly rounded anteriorly; outlined by deep but narrow axial and preglabellar furrows; lateral glabellar furrows faint. Down-sloping frontal area; anterior border with little independent convexity continues the slope of the preglabellar field in lateral view. Librigena with pointed genal angle but not extended into spine. Pygidium with margins curved steeply downward; median indentation of posterior margin; small articulating flange on anterior corner. Axis terminating short of pygidial margin but extended by post-axial ridge; two axial rings plus terminal piece. At least four pairs of firmly impressed, curved pleural furrows; interpleural furrows not expressed. Borders identifiable only as marginal regions lacking pleural furrows; border furrows absent.

Remarks

The diagnosis is modified from Rasetti’s (Reference Rasetti1961, p. 109) description of Bathyholcus and includes characters of the newly discovered librigena (Fig. 26.9, 26.10) and pygidium (Fig. 27). These additional sclerites do not clarify the affinities of the genus, which remain uncertain; without an outgroup for comparison, characters are unpolarized and the diagnosis is descriptive, rather than a list of potential synapomorphies.

Figure 26.

Bathyholcus punctatus n. sp., Shallow Bay Formation, western Newfoundland. (1–8, 11, 12) Cranidia. (9, 10) Librigena. (1–3) From boulder CH 57, Cow Head Peninsula. (4–12) From boulder HC 166, Hickey Cove area. (1–3) GSC 144619, holotype: (1) dorsal view; (2) lateral view; (3) anterior view. (4–6) GSC 143206, paratype: (4) lateral view; (5) anterior view; (6) dorsal view. (7) GSC 144620, paratype, dorsal view. (8) GSC 144621, paratype, dorsal view. (9, 10), GSC 144622, paratype: (9) dorsal view; (10) lateral view. (11) GSC 144623, paratype, dorsal view. (12) GSC 144624, paratype, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 26. Long description

Twelve photographs of cranidia and a librigena of Bathyholcus punctatus. White scale bars represent 1 mm.

Photographs 1–3 show dorsal, lateral and anterior views, respectively, of the holotype cranidium with the GSC catalogue number 144619. The dorsal view (1) shows a large palpebral lobe and short frontal area with a shallow anterior border furrow. The lateral (2) and anterior (3) views show the steep forward slope of the frontal area.

Photographs 4–6 show lateral, anterior and dorsal views, respectively, of a paratype cranidium with the GSC catalogue number 143206. All three views show the deep, slot-like axial and preglabellar furrows that are characteristic of Bathyholcus.

Photograph 7 shows a dorsal view of a paratype with the GSC catalogue number 144620. It shows the punctate external surface that defines the species.

Photograph 8 shows a dorsal view of a paratype cranidium with the GSC catalogue number 144621, highlighting the deep axial furrows.

Photographs 9 and 10 show dorsal and lateral views of a paratype librigena with the GSC catalogue number 144622. Both views show the distinctive pointed corner (genal angle).

Photograph 11 shows a doral view of a paratype cranidium with the GSC catalogue number 144623, and which clear surface punctation.

Photograph 12 is a damaged paratype cranidium with the GSC catalogue number 144624, showing the shapes of the glabellar furrows.

Figure 27.

Pygidia of Bathyholcus punctatus n. sp., Shallow Bay Formation, western Newfoundland. (1–5, 9) From boulder CH 57, Cow Head Peninsula. (6–8) From boulder HC 166, Hickey Cove area. (1, 2) GSC 144625, paratype: (1) dorsal view; (2) posterior view. (3, 4) GSC 144626, paratype: (3) dorsal view; (4) posterior view. (5) GSC 144627, paratype, dorsal view. (6) GSC 144628, paratype, dorsal view. (7, 8), GSC 143207, paratype: (7) dorsal view; (8) posterior view. (9) GSC 144629, paratype, dorsal view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 27. Long description

Nine photographs of t pygidia of Bathyholcus punctatus.

Photographs 1 and 2 show dorsal and posterior views of a paratype with the GSC catalogue number 144625. Both views highlight a tapering central axis with four distinct rings and a smooth posterior border.

*.

Photographs 3and 4 display a dorsal and anterior views of a paratype with the GSC catalogue number 144626, showing a finely pitted surface texture.

*Photograph 5 is a dorsal view of a paratype with the GSC catalogue number 144627. It is an internal mold that displays the interpleural furrows on the pleural field.

Photograph 6 is a dorsal view of a paratype with the GSC catalogue number 144628., It is a large specimen, and is relatively longer and narrower than other, smaller specimens.

photographs 7 and 8 show dorsal and posterior views of a paratype withG with the GSC catalogue number 143207. Both views show the pleural furrows and the segmentation of the axis.

Photograph 9 is a dorsal view of a paratype with the GSC catalogue number 144629, a small, well-preserved pygidium with deep pleural furrows.

Shergold and Webers (Reference Shergold and Webers1992, p. 135) compared Bathyholcus to Didwudina Ivshin, Reference Ivshin1962, going so far as to suggest (p. 135) that “there would be some justification for regarding these genera as synonymous.” Didwudina, which Ivshin assigned to family Marjumiidae Kobayashi, Reference Kobayashi1935, is documented by small photographs (Ivshin, Reference Ivshin1962, pl. 11, figs. 4–13) that provide limited information. As noted by Shergold and Webers (Reference Shergold and Webers1992, p. 136), Didwudina lacks the deep, slot-like axial and preglabellar furrows that characterize all species of Bathyholcus, although they speculated that the furrows might have been accentuated in Rasetti’s photographs. However, we can affirm that the furrows are genuinely deep and narrow in Bathyholcus and may well prove to be a synapomorphy uniting the Laurentian species. Didwudina resembles Bathyholcus in possessing a relatively short, down-sloping frontal area. However, other characters, including the very narrow (tr.) palpebral area of the fixigena and anteriorly rounded glabella, distinguish Didwudina. It is unlikely that Didwudina is related to Bathyholcus, and we see no reason to treat them as synonyms.

The aspinose librigena (Shergold and Webers, Reference Shergold and Webers1992, pl. 3, fig. 9) of Bathyholcus? conifrons Shergold and Webers, Reference Shergold and Webers1992, from the Minaret Formation, West Antarctica, is comparable to B. punctata n. sp. (Fig. 26.9, 26.10). However, B.? conifrons differs by possessing an anteriorly tapered glabella, and the axial and preglabellar furrows, although clearly defined, are not the deep, narrow grooves that characterize Laurentian species. It is doubtful that it belongs in Bathyholcus.

The glabellar outline, librigena with a pointed corner, steeply sloping frontal area, punctate cranidial sculpture, convex pygidial axis with postaxial ridge, and well-defined pleural furrows are features of B. punctatus n. sp. that are shared with some species of Ptychopleurites Kobayashi, Reference Kobayashi1936b (Ludvigsen, Reference Ludvigsen1982, fig. 66H–U). There are obvious differences in Bathyholcus, including the less strongly arched pygidium with an unusual articulating flange on the anterior corner (Fig. 27.3), the longer, relatively effaced frontal area, and larger palpebral lobe. At present, we are not tempted to assign Bathyholcus to family Leiostegiidae Bradley, Reference Bradley1925.

Bathyholcus punctatus new species

Figures 26, 27

Holotype

A cranidium (GSC 144619; Fig. 26.1–26.3) from Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland.

Paratypes

Four pygidia (GSC 144625, Fig. 27.1, 27.2; GSC 144626, Fig. 27.3, 27.4; GSC 144627, Fig. 27.5; GSC 144628, Fig. 27.6) from boulder CH 57. Five cranidia (GSC 143206, Fig. 26.4–26.6; GSC 144620, Fig. 26.7; GSC 144621, Fig. 26.8; GSC 144623, Fig. 26.11; GSC 144624, Fig. 26.12), a librigena (GSC 144622, Fig. 26.9, 26.10), and two pygidia (GSC 144628, Fig. 27.6; GSC 143207, Fig. 27.7, 27.8) from boulder HC 166, Hickey Cove area.

Diagnosis

A species of Bathyholcus with shallow cranidial anterior border furrow that extends across full width (tr.) of cranidium, a medial node on LO, and a punctate external surface.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head and boulder HC 166, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Description

Cranidium strongly arched, slopes steeply forward beyond palpebral lobes (Fig. 26.2), with length (sag.) equal to 89% (84–95%) of width across palpebral lobes. Frontal area accounts for 17% (15–20%) of cranidial length. Anterior border furrow extends across full width (tr.) of frontal area, shallow in front of glabella, but deepens slightly abaxially on some specimens (Fig. 26.6). Anterior border occupies 47% (45–53%) of frontal area length (sag.); has little independent convexity and continues slope of preglabellar and preocular fields (Fig. 26.2, 26.4). Axial and preglabellar furrows deep, narrow grooves. Glabella tapers gently forward, anterior margin slightly rounded, width (tr.) at SO equal to 72% (69–75%) of glabellar length (sag.). SO well incised and transverse medially, narrowing (exsag.) and curving forward abaxially. LO with gently curved posterior margin, accounts for 15% (13–17%); median node present (Fig. 26.1, 26.6, 26.12). Lateral glabellar furrows weakly incised, expressed most clearly on internal molds. S1 geniculate, S2 oblique, S3 faint, short (tr.), nearly transverse (Fig. 26.11, 26.12). L1 occupies 26% (25–28%) of glabellar length; L2 shorter (exsag.), equal to 19% (14–22%) of glabellar length; L3 accounts for 12% (9–14%). Palpebral area flat, width equal to 45% (40–47%) of glabellar width at SO. Palpebral lobe broad (tr.), arcuate, extending from anterior third of L1 to just beyond S2, with length (exsag.) equal to 38% (34–44%) of glabellar length; distance from posterior tip of palpebral lobe to posterior cranidial margin equal to 21% (20–23%) of cranidial length (sag.). Palpebral furrow shallow, outwardly curved groove. Anterior branches of facial sutures nearly parallel between palpebral lobes and anterior border furrow, then converge abruptly inward along anterior border, posterior branches diverge along faintly sigmoid paths. Posterior border furrow narrow groove; posterior border narrow (exsag.) near axial furrow, lengthens abaxially. External surface of exoskeleton pitted (Fig. 26.1), with pits coarser and more widely spaced in smallest specimen (Fig. 26.7).

Librigena without genal spine but with pointed genal angle (Fig. 26.9). Librigenal field broad (tr.), flexed steeply downward. Lateral border strongly convex, separated from librigenal field by shallow, moat-like border furrow. Border with faint terrace ridges; librigenal field with weak cecal network.

Pygidium roughly semielliptical in outline, with small articulating flange at anterior corner (arrowed on Fig. 27.3) and median embayment of posterior margin, length (sag.) equal to 55% (53–61%; highest value in largest specimen) of maximum pygidial width (tr.), opposite second axial ring furrow. Axis convex, raised well above pleural field, occupies 76% (74–78%) of pygidial length (sag.); axis width at first ring equal to 35% (33–41%; highest value in largest specimen) of maximum pygidial width. Two transverse axial rings and terminal piece, which may include faint, incomplete ring furrow at anterior; semielliptical articulating half-ring represents 15% (13–17%) of axis length, terminal piece accounts for 44% (40–48%) of length and tapers backward; articulating and axial ring furrows clearly expressed. Postaxial ridge terminates just short of pygidial margin. Pleural field flat near axis but curved steeply downward near margins. Five pairs of pleural furrows become increasingly oblique toward rear; anterior pair deeper than other pairs. Border expressed as marginal unfurrowed region; doublure extends inward beyond inner edge of border (Fig. 27.1). Crest of axis and pleural bands with fine punctae augmented by scattered fine granules; border mostly granulose.

Etymology

From punctatum (Latin), “a small hole,” in reference to the pitting of the external surface of the exoskeleton.

Remarks

Species of Bathyholcus are differentiated by the expression of the anterior border and border furrow. Bathyholcus gaspensis has a border furrow that is all but absent medially but deepens abruptly near the sutural margin of the cranidium (Rasetti, Reference Rasetti1961, pl. 23, figs. 18–23). By contrast, B. sulcatus Rasetti, Reference Rasetti1961, which is known only from the holotype (Rasetti, Reference Rasetti1961, pl. 23, figs. 24–26), has a well-incised border furrow. Bathyholcus punctatus resembles B. sulcatus in possessing a border furrow that is expressed across the frontal area, but it is noticeably shallower (Fig. 26.1–26.8, 26.11, 26.12), although it deepens slightly abaxially in some specimens. Sculpture is not evident on his photographs, but Rasetti (Reference Rasetti1961, p. 110) described the external surfaces of both B. gaspensis and B. sulcatus as finely granulose. The external surface of B. punctatus is finely (Fig. 26.1–26.3) to coarsely (Fig. 26.7) punctate. A minor but apparently persistent difference is the presence of a median occipital node in B. punctatus (Fig. 26.1, 26.6, 26.12).

Genus Tholifrons Palmer, Reference Palmer1968

Type species

Tholifrons advena Palmer, Reference Palmer1968 from the Jones Ridge Limestone, Hillard Peak area, Alaska (by original designation).

Diagnosis

Narrow (tr.) glabella without lateral furrows. Palpebral lobes centered a little behind glabellar mid-length. Palpebral furrows well-incised grooves, terminating abruptly at palpebral ridge. Anterior border forms very narrow (sag.) rim medially but disappears abaxially; preglabellar field very long, evenly sloping forward. Axial furrows slit-like over most of length, shallowing abruptly anteriorly at level of palpebral ridge. Librigena with broad-based genal spine.

Remarks

High-resolution digital images of what are likely three distinct species of Tholifrons from the Shallow Bay Formation show features that are difficult to discern on previously published photographs (Palmer, Reference Palmer1968, pl. 9, figs. 17–25). All of these species possess an exceedingly short anterior border medially that is easily overlooked (Fig. 28.1, 28.2, 28.4, 28.6, 28.12, 28.14, 28.15). Along most of the length of the glabella, the axial furrows are narrow but clearly defined slits, but they shallow abruptly at the intersection with the palpebral ridges (Fig. 28.1, 28.10, 28.11, 28.12, 28.14, 28.15); an abrupt termination of the finely etched palpebral furrow also occurs at the palpebral ridge (Fig. 28.9, 28.13, 28.15). We have included these characters in a revised diagnosis for the genus.

Figure 28.

Cranidia of Tholifrons, Shallow Bay Formation, western Newfoundland. (1–11) From boulder CH 57, Cow Head Peninsula. (12–14) From boulder HC 166, Hickey Cove area. (15–17) From boulder CH 66, Cow Head Peninsula. (1–11) Tholifrons maritima n. sp. (1–4) GSC 143209, holotype: (1) dorsal view; (2) anterior-oblique view; (3) lateral view; (4) anterior view. (5–7) GSC 144630, paratype: (5) anterior view; (6) dorsal view; (7) lateral view. (8) GSC 144631, paratype, dorsal view. (9) GSC 144632, paratype, dorsal view; (10), GSC 144633, paratype, dorsal view; (11) GSC 144634, paratype, dorsal view. (12–14) Tholifrons sp. 1. (12) GSC 144635, dorsal view. (13) GSC 144636, dorsal view. (14) GSC 144637, dorsal view. (15–17) Tholifrons sp. 2, GSC 144638: (15) dorsal view; (16) anterior view; (17) lateral view. Scale bars (each pertaining to all images with the same catalog number) = 1 mm.

Figure 28. Long description

Seventeen photographs of cranidia of three species of Tholifrons. White scale bars represent 1 mm.

Photographs 1 to 4 are dorsal, anterior-oblique, lateral and anterior views, respectively of the holotype with the GSC catalogue number 143209. The dorsal view (1)showing an elongate glabella and a very short anterior border. The other views show that the glabella slopes forward anteriorly.

Photographs 5-7 are anterior, dorsal and lateral views of a paratype with the GSC catalogue number 144630. The dorsal (6) view shows the palpebral lobe and furrow.

Photograph 8 shows a dorsal views of small paratype with the GSC catalogue number 144631. It has a shorter frontal area than larger specimens.

Photographs 12 to 14 show dorsal views of cranidia of Tholifrons species 1, with GSC catalogue numbers 144635, 144636, and 144637. These specimens exhibit a similar structure to T. maritima but with a frontal area that is more rounded and less tapered.

Photographs 15 to 17 show dorsal, lateral, anterior and lateral views, respectively, of Tholifrons species 2, specimen with the GSC catalogue number 144638. All three views show the wide fixigena that characterizes this species.

Paraphoreotropis Clark in Clark and Shaw, Reference Clark and Shaw1968, from the Gorge Formation of Vermont, is closely related to Tholifrons but differs in the morphology of the frontal area. Tholifrons has an evenly sloping preglabellar field (Fig. 28.2, 28.3, 28.16, 28.17), whereas Paraphoreotropis has a preglabellar field that is curved steeply downward anteriorly and apparently has a wider (tr.) anterior border (Clark and Shaw, Reference Clark and Shaw1968, pl. 53, figs. 7–10). In other respects, the two genera appear to be similar, although the published photographs of Paraphoreotropis are poor and provide few details on cranidial anatomy.

Tholifrons maritima new species

Figure 28.1–28.11

Holotype

A cranidium (GSC 143209, Fig. 28.1–28.4) from the Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland.

Paratypes

Five cranidia (GSC 144630, Fig. 28.5–28.7; GSC 144631, Fig. 28.8; GSC 144632, Fig. 28.9; GSC 144633, Fig. 28.10; GSC 144634, Fig. 28.11), also from boulder CH 57.

Diagnosis

Long frontal area; glabella of larger specimens (Fig. 28.1, 28.6) occupies slightly more than 70% of cranidial length. Anterior branches of facial suture converge forward, producing distinctly tapered cranidial outline in front of glabella.

Occurrence

Downes Point Member, Shallow Bay Formation, boulder CH 57, Cow Head, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Description

Convex cranidium elongate, strongly curved anterior margin, width (tr.) across palpebral lobes equal to 96% (92–99%) of length (sag.). Frontal area very long (sag.) and tapers forward beyond level of glabella, occupying 27% (23–29%; lowest value in smallest cranidium; Fig. 28.11) of cranidial length; evenly sloping, with very short, weakly convex anterior border expressed medially but truncated by suture abaxially; anterior border furrow absent. Axial furrows narrow, well incised, slit-like between SO and weak palpebral ridge (Fig. 28.6, 28.9); shallows abruptly forward to join weakly expressed preglabellar furrow. Glabella convex, standing well above fixigena but sloping steeply forward anteriorly (Fig. 28.3, 28.4); narrow, parallel-sided, and weakly rounded anteriorly; width (tr.) at SO equal to 54% (50–59%) of length (sag.). SO firmly impressed medially but shallows abaxially, nearly transverse. LO with curved posterior margin, accounts for 17% (15–18%) of glabellar length. Lateral glabellar furrows absent in almost all specimens; largest cranidium (Fig. 28.10) with merest hint of S1 and S2 furrows. Palpebral area of fixigena slopes very gently downward toward palpebral lobe, width equal to 70% (67–75%) of glabellar width at SO. Palpebral lobe upwardly curved flap, length equal to 31% (29–34%) of glabellar length; centered a little behind glabellar mid-length, distance from posterior tip to posterior cranidial margin (exsag.) equals 19% (17–22%) of cranidial length (sag.). Palpebral furrow narrow incised groove, terminating abruptly at oblique palpebral ridge. Anterior branches of facial suture nearly parallel opposite anterior end of glabella, then converge inward along curved paths; posterior branches diverge sharply along weakly sigmoid paths. Posterior area of fixigena flexed downward; posterolateral projection broad (tr.). Posterior border furrow forms deep groove, terminating short of sutural margin; posterior border convex, expands abaxially, roughly doubling in length (exsag.). Aside from a few faint terrace ridges on anterior border, external surface of exoskeleton smooth.

Etymology

From maritimus (Latin), “of the sea,” in reference to the occurrence of the species in shoreline exposures of the Shallow Bay Formation.

Remarks

Cranidia from CH 57 show an ontogenetic increase in the relative length of the frontal area (compare Fig. 28.6 and 28.11) from about 23% of cranidial length to about 30%. The smallest specimen from CH 57 (Fig. 28.11) is similar to the silicified holotype and paratype cranidia of Tholifrons minuta Palmer, Reference Palmer1968, but because Palmer’s specimens are illustrated in dorsal view only with small photographs, detailed comparisons with our material cannot be made. Given the limited information on the species and the small sample size, we recommend that T. minuta be restricted to the types, and we name a new species, T. maritima, for the cranidia from CH 57.

Tholifrons advena Palmer, Reference Palmer1968 (Palmer, Reference Palmer1968, pl. 9, figs. 17–19), from the Jones Ridge Limestone of Alaska, has a wider palpebral area of the fixigena and a relatively shorter frontal area than T. maritima. In at least the larger specimens (Palmer, Reference Palmer1968, pl. 9, fig. 17), the glabella tapers forward, but it is parallel-sided in T. maritima.

We regard most other records of Tholifrons as indeterminate species. The cranidia attributed to both T. minuta and T. advena Palmer, Reference Palmer1968 by Pratt (Reference Pratt1992, pl. 27, figs. 26–33) are too poorly preserved for a confident identification. A cranidium from the Frederick Limestone of Maryland apparently has an anterior border (Rasetti, Reference Rasetti1961, p. 122), although it is not evident in Rasetti’s (Reference Rasetti1961, pl. 25, fig. 21) photograph. Again, there is not enough information for an identification at the species level. Theokritoff’s (Reference Theokritoff1984, fig. 1Q, R) images of a cranidium from New York are poorly oriented, but it differs from other published specimens in having palpebral lobes that are located farther back, apparently extending posteriorly almost to the level of the border furrow.

Tholifrons sp. 1

Figure 28.12–28.14

Material and occurrence

Three cranidia (GSC 144635, Fig. 28.12; GSC 144636, Fig. 28.13; GSC 144637, Fig. 28.14) from the Downes Point Member, Shallow Bay Formation, boulder HC 166, Hickey Cove area, western Newfoundland. Acmarhachis kindlei Fauna (Westrop and Eoff, Reference Westrop and Eoff2012) and Quebecaspis conifrons Fauna.

Remarks

A few cranidia from HC 166 have less-convergent anterior branches of the facial suture, resulting in a more evenly curved anterior cranidial margin than in T. maritima. The glabella is proportionately longer, occupying slightly more than 75% of cranidial length. They may represent a distinct species, but more material is needed for a confident decision.

Tholifrons sp. 2

Figure 28.15–28.17

Material and occurrence

A cranidium (GSC 144638, Fig. 28.15–28.17) from the Downes Point Member, Shallow Bay Formation, boulder CH 66, Cow Head, western Newfoundland. Triorygma burkhalteri Fauna (Westrop and Eoff, Reference Westrop and Eoff2023).

Remarks

A single cranidium was overlooked in Westrop and Eoff’s (Reference Westrop and Eoff2023) study of a younger (Jiangshanian) fauna from the Shallow Bay Formation at Cow Head. It records a new species characterized by a wide palpebral area of the fixigena, a relatively short preglabellar field, and a glabella that expands gently forward. The posterolateral projection carries small granules, but the rest of the exoskeleton is smooth. The palpebral lobe is shorter (exsag.) than that of T. maritima.