Remarks

Bradoriids are described below following the terminology of Siveter and Williams (Reference Siveter and Williams1997), Hou et al. (Reference Hou, Siveter, Williams and Xiang-Hong2001), and Vannier et al. (Reference Vannier, Williams, Álvaro, Vizcaïno, Monceret and Monceret2005). They are oriented according to the criteria given by Hinz-Schallreuter et al. (Reference Hinz-Schallreuter, Gozalo and Liñán2007): when present, the dorsal cusp and/or the oblique ridge between one node and the dorsum are considered anterior.

Specimens recovered herein are deformed with crinkled valves (Figs. 6.1, 6.13, 7.5, 7.9, 7.19, 7.10), which are consistent with a flexible, weakly mineralized to unmineralized shield construction, which would have been secondarily phosphatized (Siveter and Williams, Reference Siveter and Williams1997; Vannier et al., Reference Vannier, Williams, Álvaro, Vizcaïno, Monceret and Monceret2005; Zhang, Reference Zhang2007; Devaere et al., Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b).

Figure 6.

Bradoriida sp. indet. A, sample TE2F, articulated, partly broken valves of specimen USTL 3235-3: (1) left lateral view, (2) oblique dorsal view, (3) ventral view, (4) oblique anterior view, (5) detail of boxed area (spine) in (4). adc = anterodorsal cusp; ads = anterodorsal spine; pdl = posterodorsal lobe; vr = ventral ridge.

Figure 7.

Bradoriida sp. indet. B, sample TE2F: (1) deformed, subamplete, articulated valves of specimen USTL 3235-2, lateral view; (2–4) articulated, partly opened valves of specimen USTL 3236-2: (2) right lateral view; (3) oblique dorsal view; (4) oblique ventral view; (5–8) partly preserved, articulated valves of specimen USTL 3235-7: (5) right lateral view; (6) oblique dorsal view; (7) anterior lobe; (8) detail of boxed area (pustulose and polygonal ornaments) in (7); (9–12) articulated valves of specimen USTL 3235-11: (9) oblique posterior view; (10) oblique dorsal view; (11) right lateral view; (12) ventral view; (13, 14) articulated valves of specimen USTL 3242-8: (13) right lateral view; (14) dorsal view showing highly projecting nodes; (15, 16) articulated valves of specimen USTL 3242-6: (15) dorsal view; (16) detail of boxed area (spinose ornamentation) in (15). Arrows point to the anterodorsal ridge. adn = anterodorsal node; adr = anterodorsal ridge; cr = connecting ridge; cs = cardinal spine; lr = lateroadmarginal ridge; pdn = posterodorsal node.

Occurrence

Sample TE2F.

Description

The valves are ~1.12 mm in length and ~741 μm in height, with a length/height ratio of ~1.5. The anterodorsal spine is ~362 μm in length. The carapace consists of two valves articulated at the dorsum. The subamplete valves are connected through a well-defined hinge line anteriorly interrupted to form a faint cusp (Fig. 6.1, 6.2). No cardinal spines were observed. The lobation consists of a slightly developed posterodorsal lobe, subparallel to the dorsal margin, extending from below the anterior cardinal corner to approximately one-third the length of the valve. The weak anterodorsal lobe is prolonged by an elongated spine (Fig. 6.4, 6.5), inclined anteriorly and bent toward the ventral margin at midheight (the orientation could be taphonomically constrained; Fig. 6.2, 6.3). Its base is extended ventrally into a narrow, well-defined ridge extending to the midlength of the valve (Fig. 6.1, 6.2). Admarginal ridges and furrows are absent. The surface does not show any other ornamental feature.

Remarks

The lack of diagnostic features precludes a definite assignment for this specimen at the family level. Nondiagnostic spines are present in a number of bradoriid species (Topper et al., Reference Topper, Skovsted, Harper and Ahlberg2013). However, their overall shape, size, and location strongly differ from the prominent, elongated anterodorsal spine observed on the specimen studied here. Its curvature toward the ventral margin seems to be taphonomically constrained, given the crinkle line observed in ventral view (Fig. 6.3). A similar anterodorsal spine connected to a ventrally extending ridge is also found in the monasteriid Monasterium oepiki Fleming, Reference Fleming1973, yet it is of Miaolingian age and lacks a posterior lobe and cusp (Hinz, Reference Hinz1992; Topper et al., Reference Topper, Skovsted, Harper and Ahlberg2013). An anterodorsal cusp characterizes only two bradoriid families, the Cambriidae and Kunmingellidae (Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001; Williams et al., Reference Williams, Siveter, Popov and Vannier2006). However, each of these show extremely short cardinal spines or prominent ventral spines (e.g., Kunmingella typica Huo and Shu, Reference Huo and Shu1985; Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001). Nonetheless, some enigmatic genera showing elongate spines on the cardinal area were tentatively assigned to those families (e.g., Isoxys Walcott, Reference Walcott1890 and Gladioscutum Hinz-Schallreuter and Jones, Reference Hinz-Schallreuter and Jones1994; Siveter et al., Reference Siveter, Williams, Peel and Siveter1996; Vannier et al., Reference Vannier, Williams, Álvaro, Vizcaïno, Monceret and Monceret2005). Their extremely fine and elongated shape is nonetheless clearly different from that observed on the specimen here.

Family Cambriidae? Lee, Reference Lee1975
Bradoriida sp. indet. B
Figures 7–9

Figure 8.

Bradoriida sp. indet. B, sample TE2F: (1–3) articulated, slightly open valves of specimen USTL 3236-6: (1) right lateral view; (2) oblique dorsal view; (3) oblique ventral view; (4–7) articulated, closed valves of specimen USTL 3236-12: (4) left lateral view; (5) oblique dorsal view, (6) dorsal view; (7) detail of boxed area in (4); (8–10) articulated valves (anterodorsal corner broken) of specimen USTL 3236-13: (8) left lateral view; (9) oblique dorsal view; (10) dorsal view; (11, 12, 16) broken valve (USTL 3235-6): (11, 12) lateral views; (16) detail of a broken spine; (13–15) articulated valves with broken ventral margin of specimen USTL 3235-4: (13) dorsal view; (14) right? lateral view; (15) detail of boxed area (spinose and polygonal ornaments) in (14); (17, 18) incomplete specimen USTL 3236-7: (17) anterolateral view showing well-developed admarginal convex area; (18) detail of boxed area (spinose ornament) in (17); (19–22) deformed, crinkled specimen USTL 3235-12 with slightly broken articulated valves: (19) lateral view; (20) detail of boxed area pustulose and polygonal ornament(in (19); (21) oblique dorsal view, (22) oblique ventral view.

Figure 9.

Bradoriida sp. indet. B, sample TE2F: (1, 2) internal mold of articulated valve of specimen USTL 3235-8: (1) left lateral view; (2) dorsal view; (3–6) articulated, subamplete valves of specimen USTL 3236-14: (3) right? lateral view; (4) oblique dorsal view; (5) detail of boxed area (superficial polygonal meshwork) in (4); (6) oblique view; (7–9) articulated valves of specimen USTL 3236-11: (7) left lateral view; (8) oblique dorsal view; (9) ventral view; (10–12) strongly flattened specimen USTL 3234-5: (10) lateral view; (11) oblique view; (12) detail of boxed area (flattened posterior lobe) in (11).

Occurrence

Sample TE2F.

Description

The valves range 679 μm−2.4 mm in length, and 338 μm−1.6 mm in height; length/height ratio ranges 1.22–2. The carapace is constituted of two subovate valves articulated at the dorsum. The orientation is inferred by the presence of a faint to well-developed, ridge-like swelling between a node and the dorsum that is considered to be the anterodorsal ridge (Fig. 7, arrow). The valves are amplete (Figs. 7.1, 7.5, 7.10, 8.14, 9.6, 9.7, 9.10) to weakly postplete and elongate (Figs. 7.2, 8.1, 8.21, 9.1). The hinge line is well defined, straight (Figs. 7.3, 7.6, 7.10, 7.13, 8.2, 8.4, 9.1) to faintly curved dorsally (Figs. 7.1, 8.1), and slightly shorter than or equal to the length of the valve. The ventral margin is rounded anteriorly, with dorsal extremities approximately perpendicular to the dorsal margin, forming nearly right cardinal corners (Figs. 7.1, 7.2, 7.11, 7.13, 8.1, 8.7). The cardinal corners, when preserved, have short cardinal spines (Figs. 7.1–7.4, 7.10, 7.11, 7.13, 8.21). The lateroadmarginal ridge is often missing (damaged?), although better preserved specimens show a discrete to well-developed, lateroadmarginal broad swelling of the ventral margin (Figs. 7.4, 8.1, 8.8, 8.17, 9.7, 9.9), in some cases bordered ventrally by a narrow flat strip (Figs. 8.3, 8.17, 9.7, 9.9). The anterodorsal and posterodorsal nodes are strongly convex, rounded, boss-like (Figs. 7.1, 7.2, 7.6, 8.1, 8.11, 8.14, 8.19, 8.21, 9.1, 9.6, 9.7) to ridge-like (Figs. 7.9, 7.11, 7.13, 8.4, 8.8), and extend from cardinal regions to the approximate midheight of the valve. They are conjoined ventrally by a slightly narrower connecting ridge, which tends to reduce or become faint at midlength (Figs. 7.2–7.6, 7.10, 7.13, 8.1, 8.17). The maximum elevation of nodes is reached toward the cardinal corners (Figs. 7.4, 7.11, 7.13, 8.3, 8.4, 8.8, 8.14). The anterodorsal node tends to be slightly better developed (Fig. 7.2–7.6). The anterodorsal ridge is a faint to well-developed, ridge-like swelling emerging dorsal to or from the anterodorsal node and extending obliquely to the approximate mid-dorsal area (Fig. 7.2, 7.6, 7.12, 7.14). On the exterior side of the anterior and posterior nodes, a large, broadly spaced, pustulose to spiny ornament (often distally abraded) tends to be distinct (Figs. 7.2, 7.3, 7.5–7.8, 7.13, 8.4, 8.6–8.9), but covers the entire surface of the valve in better-preserved and larger specimens (Figs. 7.13–7.15, 8.14, 8.17, 8.19, 8.21). The maximum length of the ornamentation spines is ~25 μm, and their maximum diameter ~35 μm. A polygonal surface ornament can be observed on thin layers overlying the spinose ornament (Figs. 7.8, 8.14–8.16, 8.19, 8.20, 9.5). Smaller specimens (Fig. 9) have a slightly different aspect. One specimen preserved as an internal mold exhibits a clear, straight hinge line (Fig. 9.1, 9.2). Otherwise, phosphatized small specimens have faint to absent connecting ridges and their surfaces are smooth, except for a fine ornament of polygonal ridges visible on one anterior node (Fig. 9.5).

Figure 10.

Pelagiella aff. P. subangulata? Tate, Reference Tate1892, sample TE2F: (1, 2) specimen USTL 3239-3: (1) basal view; (2) apertural view; (3, 4) specimen USTL 3239-4: (3) basal view; (4) apertural view; (5, 6) specimen USTL 3239-8: (5) basal view; (6) apertural view; (7, 8) specimen USTL 3239-7: (7) basal view; (8) apertural view; (9, 10) specimen USTL 3239-17: (9) dorsal view; (10) apertural view; (11, 12) specimen USTL 3239-14: (11) basal view; (12) lateral view.

Remarks

Although granulose, pustulose, and reticulate ornamentations occur in many bradoriid taxa (Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001; Vannier et al., Reference Vannier, Williams, Álvaro, Vizcaïno, Monceret and Monceret2005; Williams et al., Reference Williams, Siveter, Popov and Vannier2006; Zhang, Reference Zhang2007), broadly spaced, hollow spines have been described only in a few species (Skovsted, Reference Skovsted2005; Skovsted et al., Reference Skovsted, Brock and Paterson2006; Topper et al., Reference Topper, Skovsted, Brock and Paterson2007; Peel et al., Reference Peel, Skovsted and Wallet2021). Among those, the recovered specimens most closely resemble Spinospitella coronata Skovsted, Brock, and Paterson, Reference Skovsted, Brock and Paterson2006 in being covered by randomly distributed surface spines overlying a reticulate pattern. As in Spinospitella Skovsted, Brock, and Paterson, Reference Skovsted, Brock and Paterson2006, the spinose ornamentation on the studied specimens seems to develop in preferential parts of the carapace depending on ontogeny (Skovsted et al., Reference Skovsted, Brock and Paterson2006), being absent in the smallest specimens, restricted to the node areas in medium-sized ones, and covering the entire shield in the largest specimens. The length and shape of the spines also appear to vary throughout ontogeny, being smaller and more rounded in juvenile specimens (Fig. 8.15, 8.18, 8.20; Topper et al., Reference Topper, Skovsted, Brock and Paterson2007). Adult specimens of Spinospitella coronata also have clear connecting ridges, although this feature is only known from a single 3.4 mm long valve from North Greenland (Peel et al., Reference Peel, Skovsted and Wallet2021). Our specimens differ from Spinospitella in having boss-like rather than spine-shaped nodes occupying a more cardinal position, and in having spines with a single base lacking a distinct crown of smaller spines on their surface (Skovsted et al., Reference Skovsted, Brock and Paterson2006).

The overall morphology and position of nodes and ridges in the recovered specimens compare more closely with the cambriid genera Auriculatella Tan, Reference Tan, Yin, Ding, He, Li and Shen1980 and Cambria Neckaya and Ivanova, Reference Neckaya and Ivanova1956, which each exhibit a long commarginal ridge connecting the anterodorsal and posterodorsal nodes, a faint ridge and/or node linking the anterodorsal node to the mediodorsal margin, and a lateroadmarginal ridge between the cardinal corners (Williams et al., Reference Williams, Siveter, Hinz-Schallreuter, Melnikova, Athersuch, Horne, Lord, Siveter and Whittaker1994, Reference Williams, Siveter, Popov and Vannier2006; Siveter et al., Reference Siveter, Williams, Peel and Siveter1996; Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001; Vannier et al., Reference Vannier, Williams, Álvaro, Vizcaïno, Monceret and Monceret2005). Despite these broad similarities, our specimens differ from these cambriid genera in having spinose ornamentation and lacking the diagnostic anterodorsal cusp of the Cambriidae (sensu Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001), or an anterior cardinal corner passing into a more or less abrupt anterodorsal downslope that terminates at the anterodorsal corner (sensu Hinz-Schallreuter et al., Reference Hinz-Schallreuter, Gozalo and Liñán2007). The faint unevenness of the hinge line observed in some lateral views is either due to breakage (Figs. 7.2, 8.8), compression (Fig.7.12), or to the projection of the anterodorsal ridge beyond the dorsal margin (Fig. 7.11, 7.13). The presence of faint, straight hinge lines has already been reported in Cambriidae (Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001; Hinz-Schallreuter et al., Reference Hinz-Schallreuter, Gozalo and Liñán2007), but only in specimens preserved as open valves, which necessarily involves postmortem compression resulting in the removal of the cusps (e.g., Petrianna Siveter et al., Reference Siveter, Williams, Peel and Siveter1996, fig. 6j; Cambria danvizcainia Vannier and Siveter in Vannier et al., Reference Vannier, Williams, Álvaro, Vizcaïno, Monceret and Monceret2005, fig. 4b). Considering the very small size of the studied specimens compared to described adults (6–17.5 mm, according to Hou et al., Reference Hou, Siveter, Williams and Xiang-Hong2001), it is also likely that the Pyrenean specimens represent early growth stages that have not yet developed the diagnostic features of the family. However, the ontogeny of the Cambriidae and their morphological variations are poorly known (Williams et al., Reference Williams, Siveter, Hinz-Schallreuter, Melnikova, Athersuch, Horne, Lord, Siveter and Whittaker1994), and only highly disputable hypotheses can be made by analogy with the closest families. For instance, the appearance of the dorsal cusp in Kunmingellidae is generally mentioned in preadult stages (instar 4 of Zhang, Reference Zhang2007), at the same time as the lobation. If one considers a similar pattern among the Cambriidae, a dorsal cusp should be also present in our specimens, which exhibit distinct lobation.

Despite the absence of observable cusps, the broad resemblance between Bradoriida sp. indet. B specimens and cambriid genera (i.e., Cambria and Auriculatella) justifies their tentative attribution to Cambriidae. The absence or weak development of a connecting ridge, ornamentation, and cardinal spines in some small specimens recovered here (Figs. 8.4, 9.1, 9.7) is interpreted as being ontogenetic in origin, and tends to suggest that the differentiation of nodes precedes the development of the connecting ridge, cardinal spines, and surface sculptures in cambriid ontogeny.

Type species

Cyrtolites atlantoides Matthew, Reference Matthew1894; New Brunswick, Canada; Cambrian Stage 3?.

Diagnosis

See Kouchinsky et al. (Reference Kouchinsky, Bengtson, Clausen, Gubanov, Malinky and Peel2011).

Occurrence

Sample TE2F.

Description

The univalve conch is dextrally coiled with approximately one rapidly expanding whorl (Fig. 10.1, 10.3, 10.5, 10.7, 10.9, 10.11). The conch is asymmetrical; the spire is flat to concave on the adapical side and convex on the abapical side (Fig. 10.2, 10.4, 10.6, 10.8, 10.10). The width of the cross section rapidly expands toward the apertural region where it reaches its maximum. There, the cross section is suboval (Fig. 10.2, 10.4) to subtriangular with a slight angle on the abapical apertural margin (Fig. 10.8). The apex is slightly bulbous (Fig. 10.3, 10.5, 10.7, 10.9, 10.11). The external surface of the internal mold is smooth (Fig. 10.8, 10.12). Maximum diameter ranges 518−1.12 mm, apertural width 385−733 μm, and shell height 245−467 μm.

Remarks

The specimens described above are assigned to the genus Pelagiella due to their dextrally coiled conchs composed of one to two rapidly expanding whorls with a flattened, slightly convex or concave spiral surface (Kouchinsky et al., Reference Kouchinsky, Bengtson, Clausen, Gubanov, Malinky and Peel2011). The genus is subdivided into > 20 species, sometimes highly similar in shape and bearing intraspecific variations, which emphasizes the necessity of a systematic revision (Parkhaev, Reference Parkhaev2004; Devaere et al., Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b). Based on the lack of distinct ornamental features, any specific affiliation can only be tentative (Skovsted, Reference Skovsted2004). The above description could correspond either to Pelagiella madianensis Zhou and Xiao, Reference Zhou and Xiao1984 or to Pelagiella subangulata, yet these species bear strongly similar characters and their differences are subtle to almost nonexistent in juveniles (Parkhaev in Gravestock et al., Reference Gravestock, Alexander, Demidenko, Esakova, Holmer, Jago, Lin, Melnikova, Parkhaev, Yu, Rozanov, Yu, Ushatinskaya, Zang, Zhegallo, Zhuravlev and Yu2001). Their conspecificity has already been suggested (Parkhaev, Reference Parkhaev2004). The reduced rate of whorl coiling along with the absence of carena better recalls the shell of Pelagiella madianensis (synonymous with Pelagiella adunca Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966; Bengtson et al., Reference Bengtson, Conway Morris, Cooper, Jell and Runnegar1990; Parkhaev in Gravestock et al., Reference Gravestock, Alexander, Demidenko, Esakova, Holmer, Jago, Lin, Melnikova, Parkhaev, Yu, Rozanov, Yu, Ushatinskaya, Zang, Zhegallo, Zhuravlev and Yu2001; Parhaev, Reference Parkhaev2004). However, these two characters present considerable intraspecific and ontogenetic variation (Parkhaev, Reference Parkhaev2004). Furthermore, Pelagiella madianensis differs from Pelagiella subangulata in having a concave supraperipheral surface, which has not been noticed in the recovered specimens. Based on its apertural cross section, less extended than in Pelagiella madianensis, and its coplanar upper apertural margin and spiral, our specimens better resemble Pelagiella subangulata.

Type species

Obolus (Eoobolus) triparilis Matthew, Reference Matthew1902; Cape Breton, Canada; Wuliuan.

Diagnosis

See Balthasar (2009).

Eoobolus sp. indet.
Figures 11–13

Figure 11.

Eoobolus sp. indet.: (1, 2) specimen USTL 3250-2, sample TE1E: (1) lateral view; (2) apical view; (3) specimen USTL 3239-16, sample TE2F, lateral view; (4–8) dorsal valve of specimen USTL 3231-4, sample TE1E: (4) inner view; (5) anterior view; (6) detail of boxed area (pseudointerarea) in (4); (7) detail of boxed area (elevated pseudointerarea) in (5); (8) detail of boxed area (polygonal structures) in (6); (9–11) ventral valve of specimen USTL 3232-2, sample TE1E: (9) anterior oblique view; (10) detail of boxed area (pseudointerarea) in (9); (11) inner view; (12–15) ventral valve of specimen USTL 3232-5, sample TE2F: (12) anterior view; (13) inner view; (14) detail of boxed area (apical region) in (13); (15) detail of boxed area (polygonal structures) in (14). Avp = anterior portion of visceral platform; Mp = median projection of visceral platform; Pi = pseudointerarea; Pn = scars of pedicle nerves; Pvp = posterior portion of visceral platform; 1l = first lateral muscle scars; 2c = second central muscle scars.

Figure 12.

Eoobolus sp. indet.: (1, 2, 4) dorsal valve of specimen USTL 3253-11, sample TE1E: (1) lateral oblique view; (2) inner view; (4) anterior view; (3, 5, 6) dorsal valve of specimen USTL 3232-5 7, sample TE1E: (3) inner view; (5) oblique anterior view; (6) detail of boxed area in (3); (7–9) dorsal valve of specimen USTL 3232-6, sample TE1E: (7) inner view; (8) detail of boxed area in (7); (9) external apical view showing rounded larval shell; (10, 11) ventral valve of specimen USTL 3240-2, sample TE2F: (10) inner view; (11) detail of boxed area in (10); (12–14) dorsal valve of specimen USTL 3244-5, sample TE1E: (12) inner view; (13) detail of boxed area in (12); (14) anterior oblique view; (15, 16) ventral valve of specimen USTL 3254-1, sample TE1D: (15) inner view; (16) detail of boxed area in (15); (17, 18) ventral valve of specimen USTL 3232-10, sample TE1E: (17) inner view; (18) detail of boxed area in (17). Md = median depression; Mr = median ridge; Vl = vascular lateralia; 1c = first central muscle scar; 1l = first lateral muscle scar; 2c = second central muscle scar; 3c = third central muscle scar.

Figure 13.

Eoobolus sp. indet.: (1, 2) dorsal valve of specimen USTL 3245-15, sample TE1E: (1) inner view; (2) detail of boxed area (radiating faint ridges) in (1); (3–5) dorsal valve of specimen USTL 3250-3, sample TE1E: (3) inner view; (4) lateral view; (5) detail of boxed area (radiating fine ridges) in (4); (6–10) ventral valve of specimen USTL 3247-1, sample TE1E: (6) inner view; (7) anterior view showing emarginature; (8) detail of boxed area (polygonal structures between pseudointerarea and shell floor) in (7); (9) lateral view; (10) detail of boxed area (columnar microstructure) in (9); (11, 12) dorsal valve of specimen USTL 3247-11, sample TE1E: (11) oblique posterior view; (12) larval shell; (13–15) specimen USTL 3250-1, sample TE1E: (13) lateral view; (14) posterior view showing median sulcus; (15) external view; (16–20) juvenile articulated specimen USTL 3239-19, sample TE2F: (16) dorsal view; (17) posterior view; (18) detail of U-shaped emarginature; (19) detail of boxed area (pustulose ornament on postlarval shell) in (16); (20) detail of boxed area (pitted ornament on larval shell) in (18).

Occurrence

Samples TE2F, TE1D, TE1E.

Description

The shells are inequivalved, slightly ventribiconvex (Figs. 11.1, 11.2, 13.17) or more rarely slightly dorsibiconvex (Fig. 11.3), with the maximum width anterior to midlength. The dorsal valves are subovate to subtriangular in outline (Figs. 12.2, 12.3, 12.7, 12.12, 13.1, 13.3), and the ventral valves have an acuminate apex conferring a teardrop shape (Figs. 11.11, 11.13, 12.10, 12.15, 13.16). The pseudointerareas of both valves are subtriangular, moderately elevated above the shell floor and bear longitudinal folds or growth lines (Figs. 11.5–11.7, 11.10–11.14, 12.1, 12.4, 12.6–12.8, 12.11, 12.16, 12.18, 13.7, 13.8). Ventral pseudointerareas are bisected by strong flexure lines on each side of a narrow, deep median groove slightly widening anteriorly (Figs. 11.9–11.11, 12.10, 12.11, 13.6, 13.7). The partial preservation of the pseudointerarea shortens the extension of the pedicle groove that can be almost indistinguishable, but it can be expressed as a U-shaped emarginature on ventral valves (Figs. 11.9–11.14, 12.17, 12.18, 13.7). On dorsal valves, the groove is shallow and broad, sometimes indistinct, and the flexure lines are weak to almost absent (Figs. 11.4–11.7, 12.1–12.8). Immediately in front of the pseudointerarea lies a visceral platform that can be extended anteriorly to approximately one-third of the valve. In ventral valves, the visceral platform and its proximal projection are rarely preserved but can be inferred from scars of pedicle nerves (Fig. 11.14, 11.15) or umbonal muscles (first central muscles according to Balthasar, Reference Balthasar2009; Fig. 12.11, 12.18). In dorsal valves, the visceral area is divided into a proximal and a distal portion, yet the latter is rarely preserved or tends to disappear proximally (Fig. 11.4). It can be bisected by a median depression or ridge (Fig. 12.1–12.3).

Subovate muscle scars can be present on the posterior portion of the dorsal visceral platform, immediately beyond the flexure lines of the pseudointerarea (first lateral muscles; Fig. 11.7), or beyond the median groove (first central muscles; Fig. 12.8, 12.18). Larger, subcircular muscle scars can also occur on both sides of the median projection of the visceral platform (second central muscle scars; Figs. 11.6, 11.8, 12.5, 12.6). One specimen shows subovate, slightly diverging muscle scars on the anterior portion of the visceral platform (third central muscles; Fig. 12.12, 12.13). Some characters in vascula lateralia are weak, arcuate to straight, and begin from the proximal end of the pseudointerarea to approximately midlength of the valve, following its margins (Fig. 12.1, 12.10, 12.16, 12.18). A radiating network of fine depressions is present on the internal surface of some valves and tends to be more prominent on their peripheral parts (Fig. 13.1–13.5). Both valves can also show growth lines paralleling the valve margin on their anteriormost parts (Fig. 12.3, 12.17). Polygonal structures can be present on the posterior halves of well-preserved valves (Fig. 11.15). They tend to be best developed in dorsal valves at the junction between the second central muscle scars and the proximal margins of the posterior part of the visceral platform (Fig. 11.6, 11.8), but they can also occur between the pseudointerarea and the valve floor (Fig. 13.8). The shell microstructure consists of fine laminae separated by a dense network of transverse columns (Fig. 13.10).

The outer surface of juvenile valves shows a subcircular, strongly convex larval shell on which a lobation is tentatively inferred from weak sublinear depressions (Fig. 13.16–13.18). This structure is ornamented with a dense network of tiny pits, ~ 0.7–1.5 μm in diameter (Fig. 13.20). The postlarval shell of juvenile specimens is covered by fine, closely spaced pustules, ~7–10 μm in diameter (Fig. 13.19). Adult shells are devoid of any ornamental features and only bear fine growth lines parallel to the valve margin (Fig. 13.15). A larval shell is suggested by a rounded convex area located on the posterior end of the valve, but lacks the pitted ornament observed on juvenile specimens (Figs. 12.9, 13.11, 13.12). This area seems to consist of at least two lobes located on its proximal margin. Adult shells can also bear a shallow, broad sulcus better developed proximally (Fig. 13.13, 13.14). Measurements are provided in Table 1.

Table 1.

Measurements of ventral and dorsal valves of Eoobolus sp. indet. Il = length of pseudointerarea; Iw = width of pseudointerarea; L = length of valve; Ls = length of larval shell; MAX = maximum value; MIN = minimum value; N = number of values; SD = standard deviation; Vl = length of visceral platform; W = width of valve.

Remarks

The pustulose and pitted ornament covering adult and larval shells, respectively (Fig. 13.19, 13.20), is a diagnostic feature of the family Eoobolidae (Holmer et al., Reference Holmer, Popov, Wrona and Gazdzicki1996). Balthasar (Reference Balthasar2009) suggested abolition of the family Eoobolidae and reassigned Eoobolus to the family Zhanatellidae, pointing out the importance of preservational biases on the diagnostic features of the Eoobolidae. However, Zhang et al. (Reference Zhang, Zhang, Holmer and Li2015) noticed that most specimens of Eoobolus lack the apical emarginature on ventral valves that characterize the Zhanatellidae. As a consequence, our specimens share the diagnostic characters of the family Eoobolidae despite the lack of ornamental features on adult shells and the presence of an emarginature on most ventral valves. The specimens described above are assigned to the genus Eoobolus because of: (1) the elevated position of the pseudointerarea and its flexure lines; (2) the deep, narrow pedicle groove on the ventral valve; (3) the presence of a median projection of the visceral platform commonly bisected by a median ridge (in some cases abraded into a median depression in our specimens); and (4) the shape and position of muscle scars (Balthasar, Reference Balthasar2009). Notable differences with the genus Eoobolus include: (1) the presence of a fine network of radiating ridges on the inner side of some valves (Fig. 13.1–13.5); and (2) the diverging morphology of the third central muscle scars in one dorsal valve (Fig. 12.12, 12.13). The latter differs from the specimens of Balthasar (Reference Balthasar2009) on which exceptionally well-preserved dorsal valves show subparallel, closely spaced muscle scars separated by a prominent median ridge. Moreover, in contrast to Eoobolus, the Pyrenean specimens have a very slightly elevated pseudointerarea.

Any assignment at the specific level relies on the apical angle of the ventral valve, which seems to represent the only constant feature during ontogeny (Balthasar, Reference Balthasar2009). The ventral valves described above show apical angles ranging 50–140°, preservational biases accounting for extreme values. This high variability likely reflects the presence of multiple species in the assemblage. Of the 50 ventral valves, almost half show apical angles ranging 80–90°. This small range has already been reported for E. aff. E. viridis Cobbold, Reference Cobbold1921 from South China (Li and Holmer, Reference Li and Holmer2004; Balthasar, Reference Balthasar2009; Zhang et al., Reference Zhang, Zhang, Li and Holmer2016). Angles between 70° and 80° are also common (eight valves) and can also support assignment to either E. elatus Pelman in Pelman and Pereladov, Reference Pelman, Pereladov and Zhuravleva1986 and E. priscus Poulsen, Reference Poulsen1932, for which apical angles range 70–90° (Balthasar, Reference Balthasar2009). Finally, apical angles < 70° are also reported for seven valves, which could indicate the presence of E. triparilis among the previously listed species.

The specimens described above are different from all known species of Eoobolus in being ventribiconvex, having subequal length and width, and a short pseudointerarea, especially on dorsal valves (Table 1). The smallest length/width ratio fits E. incipiens Zhang, Popov, Holmer, and Zhang in Zhang et al., Reference Zhang, Ghobadi Pour, Popov, Holmer, Chen, Chen, Brock and Zhang2021 (averaging 1.09) and the synonym E. aff. E. viridis from Australia (averaging 1.15; Ushatinskaya and Holmer in Gravestock et al., Reference Gravestock, Alexander, Demidenko, Esakova, Holmer, Jago, Lin, Melnikova, Parkhaev, Yu, Rozanov, Yu, Ushatinskaya, Zang, Zhegallo, Zhuravlev and Yu2001), yet the typical apical angle is much more gentle (100–110°). Dorsal pseudointerareas of E. cf. E. triparilis from Canada occupy 14% of the valve length and 50% of the valve width (Balthasar, Reference Balthasar2009), which is identical to our mean measurements (Table 1). However, the pseudointerareas on ventral valves are far more extended and each bears a strongly acute apical angle. The valves described above are more similar to E. aff. E. viridis from China in having an apical angle of mostly 80–90°, a short pseudointerarea (compared to specimens from Australia), a diverging median groove, weak to indistinct flexure lines on dorsal valves, and a median sulcus (Li and Holmer, Reference Li and Holmer2004). The pustulose ornamentation of the Chinese material, large and coarsely distributed, is also a distinctive feature shared with the specimens from the Terrades inlier. The valves described above differ from Chinese specimens in having a less-elevated median ridge, yet this feature probably derives from abrasion. The shallow, poorly defined radiating ridges observed here are also seen in specimens from South Australia, referred to E. priscus (see Paterson et al., Reference Paterson, Skovsted, Brock and Jago2007, fig. 3C), but their sporadic occurrence questions their taxonomic significance. Polyspecificity is not excluded given the high variability of the studied specimens, for instance shown by the broad range of apical angle values.

Polygonal patterns (Figs. 11.8, 11.15, 13.7) have already been reported for a number of brachiopod taxa including Eoobolus (Balthasar, Reference Balthasar2009). Similar structures on the valve interiors of acrotretid brachiopods have been interpreted as molds of various types of epithelial cells distributed across distinct areas of the shell (Zhang et al., Reference Zhang, Zhang, Li and Holmer2016).

Type species

Microcornus parvulus Mambetov, Reference Mambetov1972; Kazakhstan; Cambrian Age 3.

Diagnosis

See Kouchinsky et al. (Reference Kouchinsky, Bengtson, Clausen and Vendrasco2015).

Occurrence

Sample TE2F.

Figure 14.

Microcornus cf. M. petilus Bengtson in Bengtson et al., Reference Bengtson, Conway Morris, Cooper, Jell and Runnegar1990, sample TE2F: (1, 2) specimen USTL 3238-10: (1) dorsal view; (2) apertural view; (3–5) specimen USTL 3238-1: (3) apertural view; (4) dorsal view; (5) detail of boxed area (weak polygonal patterns on surface of internal mold) in (4); (6) specimen USTL 3238-16, lateral view; (7) specimen USTL 3238-4, lateral view.

Description

The conch is broadly orthoconic, 1–1.25 mm in length, with straight lateral margins and small apical angle (Fig. 14.1, 14.4, 14.6, 14.7). The ventral side is flattened to weakly convex, and the lateral sides are rounded, forming two longitudinal ridges (Fig. 14.2, 14.3). The dorsal side is strongly convex bearing a weak median longitudinal ridge, producing a triangular cross section with rounded edges (Fig. 14.2). The protoconch is bulbous, tapering into a nearly straight, rounded tip (Fig. 14.1, 14.4–14.7). It is separated from the mature conch by a shallow constriction (Fig. 14.1, 14.4, 14.5). Three specimens exhibit a weak polygonal network on the surface of the bulbous protoconch, gradually disappearing after the constriction (Fig. 14.4–14.7). Neither opercula nor ligula were observed. The apertural width and height range 350–435 μm and 170–215 μm, respectively. The apical angle is ~15°.

Remarks

The specimens described above are assigned to the genus Microcornus based on their overall shape with a bulbous protoconch, a median ridge on the dorsal side, and the resulting rounded triangular cross section (Bengtson et al., Reference Bengtson, Conway Morris, Cooper, Jell and Runnegar1990; Malinky and Skovsted, Reference Malinky and Skovsted2004). The narrow conical morphology of the conchs produced by a small apical angle, along with the weakly convex ventral side, conforms to Microcornus petilus (see Bengtson et al., Reference Bengtson, Conway Morris, Cooper, Jell and Runnegar1990; Demidenko in Gravestock et al., Reference Gravestock, Alexander, Demidenko, Esakova, Holmer, Jago, Lin, Melnikova, Parkhaev, Yu, Rozanov, Yu, Ushatinskaya, Zang, Zhegallo, Zhuravlev and Yu2001; Malinky et al., Reference Malinky, Wilson, Holmer, Lardeux, Webby, Paris, Droser and Percival2004; Topper et al., Reference Topper, Brock, Skovsted and Paterson2009). However, the specimens recovered here differ from Microcornus petilus in having a poorly defined dorsal ridge and in lacking an ornament of fine wrinkles parallel to the apertural margin. Moreover, three specimens exhibit an unusual polygonal network on the bulbous protoconch. Such a pattern has never been mentioned on internal molds of hyolithids, and probably reflects the ornamentation of the inner surface of the conch.

Type species

Paragloborilus mirus He in Qian, Reference Qian1977; Maidiping, Emei County, Sichuan Province, South China; Fortunian.

Diagnosis

See Parkhaev and Demidenko (Reference Parkhaev and Demidenko2010).

Occurrence

Sample TE2F.

Figure 15.

Cupitheca sp. indet., sample TE2F: (1, 2) specimen USTL 3238-19: (1) lateral view; (2) apical view; (3, 5, 6, 9, 11) specimen USTL 3238-9: (3) lateral view; (5) detail of larger boxed area (faint transverse striations) in (3); (6) detail of smaller boxed area (pits on external coating) in (3); (9) apical view; (11) detail of boxed area (phosphatic rods and corresponding pits) in (9); (4, 10) specimen USTL 3238-15: (4) apical view; (10) detail of boxed area (phosphatic rods) in (4); (7, 8) specimen USTL 3238-14: (7) lateral view; (8) apical view.

Description

The conchs slowly and uniformly expand from a closed termination to an invariably broken abapical part (Fig. 15.1, 15.3). The maximum preserved length ranges 426 μm−1.15 mm, the maximum abapical diameter of the conch 224–813 μm, and the diameter of the rods 2.5–6 μm. The cross section is subcircular to oval. The closed termination (apex) is slightly (Fig. 15.1) to strongly (Fig. 15.7) convex and a shallow but well-defined constriction separates it from the conch (Fig. 15.1–15.3, 15.7–15.9). At the apex, internal and external coatings of the conch wall connect with transverse phosphatic rods expressed as tiny pits on the surface of the external coating (Fig. 15.4, 15.9–15.11). The external coating exhibits faint transverse striations (Fig. 15.3, 15.5).

Remarks

The recovered conchs are assigned to the genus Cupitheca based on their gently tapering conical shape with a convex apex separated by a marked constriction. Their identification at the specific level remains open because the ornamentation of faint transverse striations is not typical of any species of Cupitheca. The evidence of faint annular sculpture on the external surface, together with the presence of rod-like microstructure, is comparable to one specimen of Cupitheca holocyclata Bengtson in Bengtson et al., Reference Bengtson, Conway Morris, Cooper, Jell and Runnegar1990 described by Malinky and Skovsted (Reference Skovsted2004, fig. 12A).

Type species

Kelanella altaica Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966; Altai Mountains, Siberian Platform, Russia; Cambrian Age 5.

Diagnosis

See Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b)

Kelanella altaica Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966
Figures 16–19

Figure 16.

Type A sclerites of Kelanella altaica Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966: (1–3) specimen USTL 3242-13, sample TE2F: (1, 2) lateral views; (3) upper view; (4–6, 10–12) specimen USTL 3248-2, sample TE1E: (4) lateral view; (12) detail of boxed area (gridded ornament) in (4); (5, 6) lateral views showing duplicature; (11) detail of boxed area in (6); (10) apertural view; (7–9) specimen USTL 3242-3, sample TE2F: (7) apertural view; (8, 9) lateral views.

Figure 17.

Type B sclerites of Kelanella altaica Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966, specimen USTL 3248-8, sample TE1E: (1–3) lateral views; (4) detail of boxed area in (3); (5) apical view; (6) detail of boxed area in (5); (7) detail of boxed area (weak growth lines) in (6). Arrows point to deep sulcus.

Figure 18.

Type C sclerites of Kelanella altaica Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966: (1, 2, 7, 12) specimen USTL 3254-2, sample TE1D: (1) lateral view; (2) oblique apical view; (7) apertural view; (12) detail of boxed area in (2); (3–6) specimen USTL 3248-1, sample TE1E: (3) lateral facet; (4) duplicature; (5) gridded facet; (6) apical view; (8–10, 15) specimen USTL 3248-5, sample TE1E, lateral views: (8) gridded facet; (9) transverse septa; (10) duplicature; (15) detail of boxed area in (9); (11, 13, 14) specimen USTL 3243-7, sample TE2F: (11) apical view; (13) lateral view showing gridded facet; (14) lateral view showing lateral facet.

Figure 19.

Sclerites of Kelanella altaica Missarzhevsky in Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966: (1–4) Type E: (1–3) specimen USTL 3249-2, sample TE1E, lateral views: (1) gridded and single lateral facets; (2) duplicature and lateral facet; (3) gridded facet; (4) specimen USTL 3243-8, sample TE2F, lateral view showing gridded facet and single lateral facet; (5, 6) specimen USTL 3248-6 (unrecognizable type), sample TE1E: (5) internal cavity with transverse septa; (6) detail of boxed area (polygonal network on septa) in (5).

Holotype

GIN 3470/95 (Rozanov and Missarzhevsky, Reference Rozanov and Missarzhevskiy [Missarzhevsky]1966, p. 95, pl. 11, fig. 6, pl. 13, fig. 9); Altai Mountains, Siberian Platform, Russia; Kameshkovsky horizon.

Occurrence

Samples TE2F, TE1D, and TE1E.

Description

Following the nomenclature of Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b), four morphological types (A−C, E) were identified herein. Type A sclerites (Fig. 16) are bilaterally symmetric to subsymmetric, the apex slightly bending over the duplicature (Fig. 16.1, 16.2). The cross section is crescent-shaped (Fig. 16.7, 16.10). The broad convex facet shows a gridded ornament that consists of a radiating network of irregularly spaced longitudinal folds and more discrete transverse ribs (Fig. 16.3, 16.4, 16.8, 16.12). This ornamentation is well developed in the apertural region and gradually disappears toward the apex (Fig. 16.3). The opposite, concave duplicature shows fine subparallel transverse growth lines slightly curving to the apical region following the shape of the apertural margin (Fig. 16.5, 16.6, 16.11). They seem to be continuous with the transverse ridges of the gridded facet (Fig. 16.11). Reduced lateral facets are present between the gridded facet and the duplicature (Fig. 16.5).

Type B sclerite (Fig. 17) is asymmetrical, polyhedron-shaped, and wider than Type A (Fig. 17.3, 17.5). The centrally situated apical area (apex not preserved) gently curves over the duplicature (Fig. 17.1, 17.2). The weakly convex gridded facet displays a subparallel, closely spaced network of transverse ridges overlapping irregularly spaced longitudinal folds radiating from the apical region (Fig. 17.3, 17.4). The asymmetry of the specimen is based on a deep sulcus situated on the convex gridded facet, extending from the apical region to the aperture, where it is expressed as a notch (Fig. 17.2, 17.3). The slightly convex duplicature bears fine subparallel growth lines that are prolonged into more elevated ridges in two lateral facets (Fig. 17.5–17.7). The suboval cross section is visible in the apical region due to breakage (Fig. 17.5, 17.6).

Type C sclerites (Fig. 18) are slightly asymmetrical (Fig. 18.4, 18.5) with a subrectangular cross section (Fig. 18.2, 18.6, 18.7, 18.11). The apertural region is more or less strongly curved over the duplicature (Fig. 18.1, 18.2, 18.6, 18.11, 18.14). The gridded facet is concave to weakly convex (Fig. 18.2, 18.6). The opposite duplicature varies from concave toward the aperture to planar in the apical region (Fig. 18.6, 18.7, 18.11). It can bear a fine network of subparallel growth lines, gradually curving toward the apical region (Fig. 18.4, 18.10). The gridded facet and the duplicature are separated by two concave-to-planar lateral facets (Fig. 18.1, 18.3, 18.11, 18.14). The ornamentation of the gridded facet consists of well defined, broad longitudinal folds that tend to disappear toward the apical region (Fig. 18.1, 18.2, 18.12). These irregularly spaced radiating lines are overlapped by weaker transverse ridges in a gridded arrangement. In some specimens, the lateral facets bear a transitional ornamentation consisting of discrete to absent longitudinal folds and well-defined transverse ridges gradually attenuating toward the duplicature margin (Fig. 18.3, 18.11, 18.14). Our largest specimen shows, nonetheless, a strongly gridded ornamentation on its lateral facets (Fig. 18.1, 18.2). Transverse internal septa have been observed in broken specimens (Fig. 18.6, 18.9, 18.10, 18.15).

Type E sclerites are asymmetrical and slightly twisted (Fig. 19.1, 19.2). The apical area is strongly curved toward the duplicature (Fig. 19.2, 19.3). The gridded facet is partially separated from the opposite concave duplicature by a single, subplanar to concave lateral facet (Fig. 19.1, 19.2, 19.4). The transition between the lateral facet and the duplicature can be marked by a weak longitudinal crest (Fig. 19.2). The ornamentation on the gridded facet consists of broad longitudinal folds radiating from the apex, superimposed by thinner transverse ridges (Fig. 19.3). The lateral facet bears only well-developed transverse ribs (Fig. 19.1, 19.2, 19.4).

In one broken specimen that cannot be assigned to any type, the internal cavity shows slightly concave transverse septa, one of which possesses a polygonal network of fine ridges (Fig. 19.5, 19.6).

Measurements follow the stated dimensions of Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b). The maximum height ranges 1.2–1.9 mm for Type A, 1.6 mm for Type B, 1.2–2.1 mm for Type C, and 870 μm−2.1 mm for Type E. The length ranges 93–225 μm for Type A, unavailable for Type B, 555–875 μm for Type C, and 93–300 μm for Type E. The maximum width ranges 600 μm−1 mm for Type A, 2.4 mm for Type B, 2.7 mm for Type C, and 475 μm−1 mm for Type E.

Remarks

The sclerites described here are assigned to the genus Kelanella on the basis of their overall polyhedral shape, the presence of transverse septa and facets, one of which bears gridded ornamentation. They are specifically assigned to the Types A, B, C, and E of the species Kelanella altaica as defined by Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b). As far as the original scleritome of Kelanella altaica is unknown, the reason for the absence of Type D sclerites in the recovered assemblage remains uncertain. Sampling bias could be invoked (Type D sclerites might not be dominant in the scleritome), but potential ontogenetic and ecophenotypic effects on Kelanella altaica assemblages should also be considered. The specimens assigned to Types A, B, C, and E in the material from the Pyrenees are very similar to specimens assigned to the same morphotypes in the material from the Montagne Noire described by Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b), and comparison to other representatives of Kelanella altaica figured in the literature detailed in this publication can be followed. The single specimen assigned to Type B shows a noticeable difference with the specimens described by Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b) in the presence of fine, discrete, closely spaced growth lines on the duplicature (Fig. 17.5–17.7), along with prominent and elevated folds on the gridded facet (Fig. 17.3, 17.4). Although the affiliation of this peculiar type to Kelanella altaica was questioned by Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b), the recovery of the Type B sclerites together with other sclerites undoubtedly assigned to Kelanella altaica supports the assumption that they belong to the same scleritome. One specimen assigned to Type C, due to its quadrangular cross section, shows a strongly gridded pattern on its lateral facets (Fig. 18.1, 18.2) that had not been described for this type by Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b). The gridded pattern of the facet of some Pyrenean specimens assigned to Type A is slightly faint in way similar to those of specimens described by Rozanov and Missarzhevsky (1966). The numerous, well-illustrated specimens of Type E sclerites from China by Yuan and Zhang (Reference Yuan and Zhang1983) compare well with the material from the Pyrenees and from the Montagne Noire. Except for the left/right specimen differentiation, they show little variation. Only the transverse ribs of the lateral facets are thicker in the specimens from the Pyrenees than in those described by Yuan and Zhang (Reference Yuan and Zhang1983) and Devaere et al. (Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b).

Polygonal structures were observed on one specimen of type E in the material from the Pyrenees and have already been described for the same sclerite type in the material from the Montagne Noire (Devaere et al., Reference Devaere, Clausen, Monceret, Vizcaïno, Vachard and Genge2014b). In the case of the Pyrenean material, it is however difficult to determine whether the polygons are on the inner surface of the sclerite wall or are part of the wall structure made visible due to delamination.

Remarks

The classification of chancelloriid sclerites has continuously been reviewed following the recovery of complete scleritomes and large sclerite populations (Yun et al., Reference Yun, Zhang, Li, Pan, Li and Brock2019; Moore et al., Reference Moore, Porter, Webster and Maloof2021). However, the present assemblage only consists of a limited collection of disarticulated sclerites, some of which are not known from articulated taxa (e.g., 4 + 0 sclerites in Allonnia Doré and Reid, Reference Doré and Reid1965; Yun et al., Reference Yun, Zhang, Li, Pan, Li and Brock2019). Moreover, some species are represented only by a fraction of their known dominant sclerite types in the present assemblage (e.g., Chancelloria eros Walcott, Reference Walcott1920 is here represented only by 7 + 1 sclerites, but 6 + 1 sclerites should also be dominant in this taxon; Bengtson and Collins, Reference Bengtson and Collins2015; Moore et al., Reference Moore, Porter, Webster and Maloof2021), whereas individual sclerite types can be produced by distinct scleritomes (e.g., 4–6 + 0 types from Chancelloria Walcott, Reference Walcott1920 or Allonnia; Moore et al., Reference Moore, Li and Porter2014). We have therefore adopted a conservative approach by following traditional taxonomy (Moore et al., Reference Moore, Li and Porter2014) without assuming correspondence between sclerite-based and scleritome-based taxa.

Type species

Chancelloria eros Walcott, Reference Walcott1920; Walcott Quarry, Ontario, Canada; Cambrian Age 5.

Diagnosis

See Kouchinsky et al. (Reference Kouchinsky, Bengtson, Clausen, Gubanov, Malinky and Peel2011).

Occurrence

Sample TE2F.

Figure 20.

Chancelloriid sclerites, sample TE2F: (1–6) Chancelloria sp. indet.: (1) specimen USTL 3234-2, abaxial view; (2, 3) specimen USTL 3234-3: (2) abaxial view; (3) detail of boxed area (verruculose texture) in (2); (4) specimen USTL 3233-14, abaxial view; (5, 6) specimen USTL 3234-1: (5) abaxial view; (6) detail of boxed area in (5); (7–14) Allonnia tetrathallis (Jiang in Luo et al., Reference Luo, Jiang, Wu, Song and Ouyang1982): (7, 8) specimen USTL 3233-13, 4 + 0 type: (7) abaxial view; (8) oblique view; (9, 10) specimen USTL 3233-8, 5 + 0 type: (9) abaxial view; (10) oblique view; (11, 12) specimen USTL 3233-9, 6 + 0 type: (11) abaxial view; (12) oblique view; (13, 14) specimen USTL 3233-6: (13) abaxial view; (14) oblique view; (15–17) Archiasterella charma Moore, Li, and Porter, Reference Moore, Li and Porter2014, specimen USTL 3233-10: (15) basal view, (16) lateral view; (17) detail of boxed area (verruculose texture) in (16).

Description

The 7 + 1 sclerites consist of radiating lateral rays surrounding a larger, subvertical central ray in a star-like appearance (Fig. 20.1, 20.2, 20.4, 20.5). Lateral rays are mostly regularly oriented, straight, and parallel to the basal surface at least in their most proximal part (tips are not preserved). Rays are separated from one another by deep narrow grooves reflecting the original extent of now-dissolved, presumably calcitic walls. Grooves appear to be larger toward the sclerite center (Fig. 20.4, 20.7, 20.11), indicating larger wall thickness in this area. One specimen appears to preserve a mineral phase upon contact with the missing central ray (Fig. 20.5). However, closer inspection of this sclerite reveals the presence of a gap between radiating rays and central mineral inclusions, suggesting that the latter are likely remnants of the missing central ray. A verrucose texture produced by small, densely distributed bumps is visible on the external surface of some rays, tending to be better developed proximally (Fig. 20.3). Scale-like structures visible on the external surface of some rays can locally result in a fibrous appearance (Fig. 20.6). The maximum ray length is 1.03 mm (all fragmentary). The angle between rays varies 40–75° for irregular sclerites and is ~60° for regular ones. The diameter of the central ray ranges 352–755 μm.

Remarks

The specimens described above are assigned to Chancelloria because of their flattened basal surface consisting of seven regularly oriented lateral rays distributed over one plane, surrounding a larger, subvertical central ray (Fig. 20.1, 20.2, 20.4). Specimens from the Terrades inlier are comparable to Chancelloriella irregularis Qian, Reference Qian1989, for which 7 + 1 sclerites are common (Moore et al., Reference Moore, Li and Porter2014). However, the irregularity in orientation and shape of the lateral rays contrasts with the sclerites described above. Small cylindrical to conical bumps (Fig. 20.3) have already been reported among the Chancelloriidae and interpreted to represent infills of pores initially piercing the calcareous wall of the sclerite dissolved by acid treatment (Moore et al., Reference Moore, Li and Porter2014). Scale-like textures of internal molds (Fig. 20.6) are known from several chancelloriid genera and are interpreted to represent inclined projections of an underlying layer of aragonitic fibers (Porter, Reference Porter2008; Moore et al., Reference Moore, Li and Porter2014).

Type species

Allonnia tripodophora Doré and Reid, Reference Doré and Reid1965; Carteret, Armorican Massif, France; Cambrian Age 2?.

Diagnosis

See Moore et al. (Reference Moore, Li and Porter2014).

Holotype

[No catalog number] (Luo et al., Reference Luo, Jiang, Wu, Song and Ouyang1982, pl. 23, fig. 1); Chenggong pumping station, Kunming, Yunnan, China; upper part of Badaowan Member, Qiongzhusi Formation.

Occurrence

Sample TE2F.

Description

The 4 + 0, 5 + 0, and 6 + 0 sclerites exhibit lateral rays that bend steeply away from the basal surface; no central ray was observed. The maximum width of the rays is reached at its proximal end, tapering distally into a pointed tip (Fig. 20.8, 20.9, 20.11, 20.12). Deep and narrow grooves separate each lateral ray. In 4 + 0 sclerites, two rays bear three articulatory facets and therefore touch three other rays, whereas two rays bear two articulatory facets and are in contact with only two other rays (Fig. 20.7, 20.8). Rays bearing three articulatory facets are slightly longer than the others. The rays contact nearly at right angles to each other in abaxial view. The 5 + 0 sclerites have one larger ray in contact with the four others, two in contact with three other rays, and two in contact with two other rays (Fig. 20.9, 20.10). The 6 + 0 type sclerites are represented by two specimens with variable arrangement of the lateral rays (Fig. 20.11–20.14). The length of rays ranges 380–725 μm, the angles between rays are ~70° for 6 + 0-type sclerites and 90° for 4 + 0-type sclerites. The angle between lateral rays and the basal surface ranges 25–55° for 6 + 0 and 4 + 0 sclerite types, and is ~30° for the 5 + 0 sclerite type.

Remarks

The sclerites described above are assigned to the genus Allonnia because of the absence of a central ray and the strongly angled position of the lateral rays from the basal plane, extending out from the flattened basal surface. Within the genus, the Pyrenean sclerites are assigned to Allonnia tetrathallis due to similarities between the 4 + 0 and 5 + 0 forms already assigned to the species in the literature (see Moore et al., Reference Moore, Li and Porter2014). The 6 + 0 forms are also assigned to Allonnia tetrathallis owing to their co-occurrence and general resemblance with 4 + 0 and 5 + 0 forms. Similar 6 + 0 forms were also found in the Cambrian Puerto Blanco Formation of NW Mexico and tentatively assigned to Allonnia tetrathallis (see Devaere et al., Reference Devaere, Clausen, Sosa-León, Palafox-Reyes, Buitrón-Sánchez and Vachard2019). Nevertheless, in the absence of known scleritomes combining 4 + 0, 5 + 0, and 6 + 0 sclerites, the possibility that these sclerite types belong to different species cannot be ruled out, not least because of the similarity between 4–6 + 0 sclerites from Chancelloria and Allonnia scleritomes (see Moore et al., Reference Moore, Li and Porter2014).

Type species

Archiasterella pentactina Sdzuy, Reference Sdzuy1969; Guadalcanal basin, Cazalla de la Sierra, Sierra Morena, Spain; Cambrian Age 3?.

Diagnosis

See Moore et al. (Reference Moore, Li and Porter2014).

Holotype

NIGP 159158 (Moore et al., Reference Moore, Li and Porter2014, fig. 11H); Xiaotan, Yongshan, Yunnan, China; Shiyantou Formation.

Occurrence

Sample TE2F.

Description

The 3 + 0 sclerites, without a central ray, consist of two horizontal rays oriented parallel to the basal surface and one principal ray recurved over the other two (Fig. 20.15–20.16). In its proximal region, the principal ray is larger than the two lateral rays (Fig. 20.16), but its basal facet is smaller (Fig. 20.15). The cross section of each ray is subcircular distally and oval proximally. It is pierced on its basal facet by a central, subcircular to oval foramen that is smaller in the principal ray (Fig. 20.15). A deep, narrow, Y-shaped groove is situated close to the foramina, separating each ray. Verrucose texture is visible on the external surface of the rays, but it is better expressed distally (Fig. 20.16–20.17). The principal ray curves at ~45° above the basal surface. The angle between lateral rays is ~145°. All rays are fragmented, with a maximum length of 515 μm. The major axis of the foramina is ~156 μm for lateral rays and 93 μm for the principal ray. The minor axis is ~99 μm for lateral rays and ~55 μm for the principal ray.

Remarks

The specimens described above are assigned to the genus Archiasterella based on the absence of central rays and the coplanar position of the two lateral rays, with the principal ray recurved over the latter (Moore et al., Reference Moore, Li and Porter2014). In this genus, three-rayed sclerites have only been reported in the species Archiastrella charma.

Remarks

Due to the uncertain systematic position and paleobiology of hyolithelminth tubes, along with their conspicuously simple shape showing considerable variation, new genera and species within the order have proliferated. Discrimination among taxa relies on subtle differences related to general shape, outline of the cross section, angle of divergence, and the morphology, density, and prominence of the ornamentation. Numerous studies have shown high variability in these characters among single taxa and their probable relationship with preservational biases (e.g., Skovsted et al., Reference Skovsted, Brock and Paterson2006). Moreover, distinctions at the generic level have been questioned by the discovery of transitional forms (Paterson et al., Reference Paterson, Skovsted, Brock and Jago2007; Topper et al., Reference Topper, Brock, Skovsted and Paterson2009). Nonetheless, for reasons of clarity, traditional taxonomy is used here with open nomenclature for the following systematic analyses.

Type species

Hyolithes micans Billings, Reference Billings1871; Troy, New York, USA; Cambrian Age 4.

Hyolithellus sp. indet.
Figure 21.1–21.9

Figure 21.

Hyolithelminth tubes: (1–9) Hyolithellus sp. indet.: (1–3) specimen USTL 3245-8, sample TE1E: (1) lateral view; (2) adapical view; (3) apertural view; (4, 6, 7) specimen USTL 3246-1, sample TE1E: (4) lateral oblique view; (6) detail of boxed area (transverse growth lines) in (4); (7) cross sectional view; (5, 8) specimen USTL 3246-14, sample TE1E: (5) lateral view showing interrupted transverse rib (arrow); (8) adapical view; (9) specimen USTL 3246-6, sample TE1E, lateral view, showing interrupted transverse ribs (arrows); (10–28) Torellella? sp. indet.: (10–13) specimen USTL 3251-8, sample TE1E: (10) lateral view; (11) apertural view; (12) apical view; (13) detail of boxed area in (11); (14, 15) specimen USTL 3240-10, sample TE2F: (14) apertural view; (15) lateral view; (16–18) specimen USTL 3245-3, sample TE1E: (16) lateral view; (17) apical view; (18) apertural view; (19, 21, 27) specimen USTL 3240-9, sample TE2F: (19) apertural view; (21) lateral view; (27) detail of boxed area (faint transverse ribs) in (19); (20, 22) specimen USTL 3240-1, sample TE2F: (20) lateral view; (22) apertural view; (23–25) specimen USTL 3252-1, sample TE1E: (23) apertural view; (24, 25) lateral views showing longitudinal ridge (arrows); (26, 28) specimen USTL 3241-1, sample TE2F: (26) lateral view; (28) detail of boxed area (transverse ribs) in (26).

Occurrence

Samples TE2F, TE1D, and TE1E.

Description

The subcylindrical tubes of phosphatic composition have a subcircular cross section at both opened ends (Fig. 21.2–21.4, 21.7, 21.8). All specimens are fragmentary. They are generally slightly tapering toward one end, and straight (Fig. 21.4, 21.5, 21.9) to curved (Fig. 21.1). The external surface of the tube is either smooth (Fig. 21.4) or with regularly spaced, faint (Fig. 21.6) or irregular, dense, transverse annulations that can be interrupted at midlength (Fig. 21.5, 21.9). The length ranges 571 μm−1.7 mm, maximum diameter of the cross section 136–670 μm, and the angle of divergence 1–8°. The space between ribs ranges 20–80 μm.

Remarks

The specimens described above are assigned to the genus Hyolithellus based on their phosphatic composition, their slightly tapering cylindrical shapes, and their circular cross sections. Nearly straight tubes covered with weak and regularly spaced annulations are comparable to Hyolithellus micans, whereas tubes with more irregular, coarser ornamentation (Fig. 21.3, 21.4) are similar to Hyolithellus filiformis Bengtson in Bengtson et al., Reference Bengtson, Conway Morris, Cooper, Jell and Runnegar1990, although the available material is too fragmentary to preserve their complete curved shape (Demidenko in Gravestock et al., Reference Gravestock, Alexander, Demidenko, Esakova, Holmer, Jago, Lin, Melnikova, Parkhaev, Yu, Rozanov, Yu, Ushatinskaya, Zang, Zhegallo, Zhuravlev and Yu2001; Topper et al., Reference Topper, Brock, Skovsted and Paterson2009).

Type species

Hyolithes laevigatus Linnarsson, Reference Linnarsson1871; Sweden; Cambrian Age 3.

Remark

Phosphatic tubes with an elliptical cross section, a planar apertural margin, and transverse annulations are generally referred to Torellella (Skovsted et al., Reference Skovsted, Brock and Paterson2006). However, this genus shares an important set of features with Sphenothallus Hall, Reference Hall1847 and their distinction relies on highly subtle details, which can be strongly controlled by preservational biases (Yang, Reference Yang2014). They include ornamental features (Zhu et al., Reference Zhu, Van Iten, Cox, Zhao and Erdtmann2000), yet this criterion is delicate to take into account given the scarcity of well-preserved microstructures in the material. Another distinctive feature concerns longitudinal thickenings on the narrow sides of the tube (in transverse view). Due to the difficulties in identifying these characters, the present material is only tentatively assigned to Torellella.

Occurrence

Samples TE2F, TE1D, and TE1E.

Description

The straight (Fig. 21.20), curved (Fig. 21.14, 21.15, 21.25), or slightly undulating (Fig. 21.10, 21.19, 21.26) phosphatic tubes have an elliptical cross section (Fig. 21.11, 21.13, 21.14, 21.18, 21.19, 21.22, 21.23). The latter becomes circular adapically as the tube tapers (Fig. 21.12, 21.17). The angle of divergence (6–23°) generally increases toward the aperture (Fig. 21.15, 21.26). The apical end can bear an expanded margin separated from the rest of the tube by a low constriction (Fig. 21.15). In the apertural region, the broad sides are flat (Fig. 21.14, 21.19) to slightly convex (Fig. 21.13, 21.22). The external surface of the tubes is generally smooth but, when preserved, the external ornament consists of faint transverse ribs (Fig. 21.27, 21.28), separated by ~20 μm. Narrow sides are rounded and can exhibit fine, discrete longitudinal ridges (Fig. 21.24, 21.25). All specimens are fragmented, 938 μm−3 mm in length, and 140–813 μm in maximum diameter.

Remarks

The conical structure at the apical end could act as an attachment mechanism to the substrate, although no attachment disks were recovered.

Type species

Helenia cancellata Cobbold, Reference Cobbold1921; Comley, Shropshire, Britain; Cambrian Age 3, lower Cambrian.

Diagnosis

See Kouchinsky et al. (Reference Kouchinsky, Bengtson, Clausen and Vendrasco2015).

Holotype

CAMSM A.420a, (Cobbold, Reference Cobbold1921, pl. 24, fig. 7A); Comley, Shropshire, Britain; Callavia Zone, lower Cambrian.

Figure 22.

Rhombocorniculum cancellatum Cobbold, Reference Cobbold1921, sample TE2F: (1, 2, 7, 9) specimen USTL 3237-3: (1) lateral view; (2) apertural view; (7) detail of boxed area (cancellate ornamentation) in (1); (9) detail of boxed area (cancellate ornamentation) in (1); (3) specimen USTL 3237-1, apertural view; (4, 8) specimen USTL 3237-9: (4) apertural view; (8) detail of boxed area in (4); (5, 6) specimen USTL 3237-2: (5) apertural view; (6) detail of boxed area in (5).

Occurrence

Sample TE2F.

Description

The sclerites are elongate, variably curving to ~70°, and strongly twisting to ~90° clock- (Fig. 22.3, 22.4) or counterclockwise (Fig. 22.5). They consist of a slender type (Fig. 22.3–22.5) and a broad type, the latter represented by a single specimen (Fig. 22.1, 22.2). The slender sclerites exhibit two broad sides, one convex and the other slightly concave, and two thin margins, one thicker than the other, which can be blade-like thus producing an asymmetric drop-like cross section (Fig. 22.3–22.6, 22.8). The latter displays a small circular to oval opening, called a lumen, and is surrounded by a thick wall (Fig. 22.3, 22.4, 22.8). The lumen can also be a planar-convex, crescent-like opening paralleling the margins of the cross section, with a reduced wall (Fig. 22.5, 22.6). The external surface is covered by a cancellate ornamentation, consisting of a dense network of fine, regularly spaced tubercles (Fig. 22.1, 22.3, 22.7, 22.9). These tubercles, when well preserved, seem to be perpendicular to the surface. The broad type differs from the slender one in bearing two broad lateral surfaces, one flat and the other slightly convex, thus producing a thin, elongated, almost rectangular cross section (Fig. 22.2). In this morphotype, the lumen is small, oval in cross section, and central to the cross section of the sclerite. The sclerites are 1.09–1.74 mm in length (maximum distance between the apex and the base), 167–424 μm in width (maximum distance between the lateral sides of the basal cross section), and 47.5–120 μm in height (maximum distance between upper and lower sides of the basal cross section).

Remarks

The recovered sclerites are assigned to the genus Rhombocorniculum on the basis of their typical cancellate ornamentation, elongated shape, and the presence of a central lumen (Kouchinsky et al., Reference Kouchinsky, Bengtson, Clausen and Vendrasco2015). The diagnostic microstructure of obliquely arranged tubules covering the wall is not preserved. The recovered sclerites show a twisted shape with tubercles perpendicular to their surface and a thick wall associated with a drop-shaped cross section, which enables the assignment to R. cancellatum. However, one specimen clearly shows a reduced wall and a strongly developed opening (Fig. 22.5, 22.6), which questions its affiliation to this species. The Pyrenean specimens differ from R. insolutum Missarzhevsky in Missarzhevsky and Mambetov, Reference Missarzhevsky and Mambetov1981, which shows bifurcated, spine-like, or very broad morphotypes.

Indeterminate subconical elements
 Figure 23

Figure 23.

Indeterminate subconical elements, sample TE2F: (1–3, 6, 9) specimen USTL 3241-25: (1) lateral view; (2) posterior view; (3) basal view; (6) detail of boxed area (lamellae) in (2); (9) detail of boxed area (polygonal network and row of pustules) in (1); (4, 5) specimen USTL 3241-27: (4) lateral view; (5) detail of boxed area (papillate structures) in (4); (7, 8, 13, 14) specimen USTL 3241-21: (7) detail of boxed area (longitudinal furrows and pits) in (13); (8) basal view; (13) oblique anterior view; (14) lateral view; (10, 22, 25, 27) specimen USTL 3241-5: (10) oblique view; (22) lateral view; (25) detail of boxed area (longitudinal rows of faint ridges) in (22); (27) transverse view; (11, 16) specimen USTL 3241-20: (11) lateral view; (16) basal view; (12, 15) specimen USTL 3241-19: (12) lateral view; (15) detail of boxed area (longitudinal furrows and pits) in (12); (17, 18, 20, 21) specimen USTL 3237-14: (17) posterior view; (18) lateral view; (20) detail of boxed area (rows of pustules) in (17); (21) detail of boxed area (spinose ornament) in (18); (19, 26) specimen USTL 3241-9: (19) lateral view; (26) detail of boxed area (pustulose ornament at apex) in (19); (23, 24, 29) specimen USTL 3241-4: (23) basal view; (24) lateral view; (29) detail of boxed area (polygonal structures) in (24); (28) specimen USTL 3241-8, basal view.

Occurrence

Sample TE2F.

Description

The subconical elements are straight (Fig. 23.19, 23.22, 23.24) to curved (Fig. 23.1, 23.4, 23.11–23.14, 23.18), 329 μm−2.16 mm in length, 128–417 μm in width, and 112–267 μm in height. The degree of curvature, when observable, gently increases toward the apex where it reaches its maximum. The apex is curved toward the arbitrarily defined posterior region. When preserved, the apical tip is sharply pointed (Fig. 23.4, 23.11, 23.12, 23.14, 23.18) to slightly rounded (Fig. 23.19, 23.22, 23.26). The abapical area is generally irregularly broken but one specimen has an inflated abapical end (Fig. 23.1–23.3). The elements are laterally flattened (Fig. 23.2, 23.13, 23.17). One specimen is strongly flattened to crinkled (Fig. 23.11, 23.16). One longitudinal furrow, situated slightly posterior to the midline of each lateral side, is variably expressed, from faint (Fig. 23.1, 23.4, 23.12) to strong (Fig. 23.11, 23.14, 23.18, 23.19, 23.22, 23.24). When present, furrows gradually faint toward the apex. The posterior and anterior sides are strongly convex, so the cross section of the sclerite is 8-shaped (Fig. 23.2, 23.3, 23.8, 23.10, 23.13, 23.16, 23.17, 23.23, 23.27, 23.28) with two laterally flattened lobes. The ornamentation of the internal molds consists of broadly and regularly spaced pustules, 10–15 μm in diameter, arranged in rows on the anterior and posterior margins of the element (Fig. 23.5, 23.19, 23.20); narrow longitudinal striae or furrows and elongated pits aligned in the same direction (Fig. 23.7, 23.15); and rows of faint ridges (Fig. 23.25). Spines are also visible on the posterior margin of one specimen (Fig. 23.18, 23.21). Polygonal structures can also be observed on internal molds, surrounding the pustules on the lateral surface (Fig. 23.29). One specimen exhibits a subconical element attached to a crinkled unidentified structure (Fig. 23.17, 23.18, 23.20, 23.21).

Remarks

The crinkled specimens support the hypothesis that the shell/carapace was initially flexible. Such preservation is comparable to the bradoriids recovered from the same level. Moreover, the crinkled unidentified structure to which a conical element is connected broadly resembles that of the bradoriids. Finally, the recovered conical elements and bradoriids share similar ornamentation. Nevertheless, in the absence of articulated material, the phylogenetic affinity of these fragments remains problematic and is possibly varied. Ornamented spines comparable to the unidentified subconical elements described above have been interpreted to represent detached fragments of different panarthropod origins, including potential trilobites (Skovsted and Peel, Reference Skovsted and Peel2001; Dzik, Reference Dzik2003; Topper et al., Reference Topper, Skovsted, Brock and Paterson2007; Li et al., Reference Li, Steiner, Zhu and Zhao2012; Dzik, Reference Dzik2003; Caron et al., Reference Caron, Smith and Harvey2013; Zhang et al., Reference Zhang, Dong and Xiao2014; Kouchinsky et al., Reference Kouchinsky, Bengtson, Clausen and Vendrasco2015).