Amplexograptus maxwelli beds

Specimens referred here to Amplexograptus maxwelli (Decker, Reference Decker1935) were initially identified as the endemic species Amplexograptus gansuensis Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982. This material was reported from the Tianzhu Formation in both the Sijiagou and West Qiqiaogou sections (Mu and Zhang, Reference Mu and Zhang1964). However, Amplexograptus gansuensis was revised by Chen et al. (Reference Chen, Ni, Mitchell, Qiao and Zhan2000a) as conspecific with Amplexograptus maxwelli based on their study of similar material from the Diplacanthograptus lanceolatus Biozone of the Yingan Formation at Dawangou, Xinjiang. Elsewhere, Amplexograptus maxwelli is widely known from the late Sandbian to early Katian (Finney, Reference Finney1986; Goldman et al., Reference Goldman, Campbell and Rahl2002, Reference Goldman, Leslie, Nõlvak, Young and Bergström2007). Pseudoclimacograptus tianzhuensis Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982, illustrated by Mu (Reference Mu1963b, fig. 8c), is an endemic species, although in the West Qiqiaogou section it occurs with Amplexograptus maxwelli. Among the specimens collected by Youkui Zhang in the Tianzhu Formation from isolated outcrops at Jiutiaoling, which is located at the western margin of the present study area (Fig. 1), several are herein identified as Climacograptus bicornis. This species was widely distributed throughout the paleotropical regions during the late Sandibian age (e.g., VandenBerg and Cooper, Reference VandenBerg and Cooper1992; Goldman et al., Reference Goldman, Leslie, Nõlvak, Young and Bergström2007; Zalasiewicz et al., Reference Zalasiewicz, Taylor, Rushton, Loydell, Rickards and Williams2009; Chen et al., Reference Chen, Zhang, Goldman, Bergström, Fan, Wang, Finney, Chen and Ma2017). To sum up, only a few graptolite species occur in the Tianzhu Formation. It is difficult to erect a biozone depending on such a small fauna that was not densely collected. We refer to the strata that yield this low-diversity fauna as the Amplexograptus maxwelli beds. Taken together, the available information suggests that the Amplexograptus maxwelli beds could correspond to an interval from the upper part of Sa2 to the lower part of Ka1 intervals (Fig. 2).

Figure 2.

(1–3) Stratigraphic columns for the Sijiagou, West Qiqiaogou, and East Qiqiaogou sections, respectively, showing graptolite faunas and their biostraigraphic unit assignments (see text for discussion); SB1–SB3, SC1–SC3, SD2, SD4, Sh1–Sh6, and Sh9–Sh14 are sample numbers. (4) Inset diagramatic representation of graptolite biostratigraphic succession in the East Qilianshan sections and their likely correlation with the international Ordovician stages and stage slices of Bergström et al. (Reference Bergström, Chen, Gutiérrez-Marco and Dronov2009) and Gradstein et al. (Reference Gradstein, Ogg, Schmitz and Ogg2012) as well as to the Australasian succession of VandenBerg and Cooper (Reference VandenBerg and Cooper1992) with which the present faunas share many species.

Diplacanthograptus geniculatus-Orthograptus quadrimucronatus beds

No graptolites have been collected from the upper Tianzhu Formation in the Sijiagou section or from the Sijiagou Formation in the West Qiqiaogou section (Figs. 1, 2). However, a few graptolites, including Diplacanthograptus geniculatus and Orthograptus quadrimucronatus (Hall, Reference Hall1865) have been collected from the lower Sijiagou Formation (SB1 and 3) in the Sijiagou section. Diplacanthograptus spiniferus was discovered together with Diplacanthograptus geniculatus in the Sijiagou Formation at Jiutiaoling. Diplacanthograptus geniculatus is endemic to the study region, however, O. quadrimucronatus is a long-ranging but distinctive and common member of the Katian graptolite assemblages (Goldman, Reference Goldman1995). This species first occurs near the base of the Diplacanthograptus caudatus Biozone, at the base of the Katian and ranges upward into the late Katian Dicellograptus complanatus Biozone (Koren’ et al., Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983; VandenBerg and Cooper, Reference VandenBerg and Cooper1992; Mitchell et al., Reference Mitchell, Goldman, Cone, Maletz and Janousek2003; Goldman et al., Reference Goldman, Leslie, Nõlvak, Young and Bergström2007). In Kalpin, Xinjiang, it occurs from the D. lanceolatus to the Diplacanthograptus spiniferus biozones (Chen et al., Reference Chen, Ni, Mitchell, Qiao and Zhan2000a). Diplacanthograptus spiniferus is also widely distributed in the early Katian strata. The type material originates from the Utica Shale (Ruedemann, Reference Ruedemann1912, Reference Ruedemann1947) in eastern North America, where it characterizes the eponymous biozone (Riva, Reference Riva1974a), although that unit represents only a portion of the global duration of this species (Bergström and Mitchell, Reference Bergström and Mitchell1990). In Scotland, this species first appears in the lower part of the middle Caradocian Dicranograptus clingani Biozone (Ka1) and ranges upward into the overlying late Caradocian Pleurograptus linearis Biozone (Ka2) (Zalasiewicz et al., Reference Zalasiewicz, Taylor, Rushton, Loydell, Rickards and Williams2009). In Australia, it occurs within the Climacograptus baragwanathia (Ka1, Ea2) to the Dicellograptus gravis (Ka2, Ea4) biozones (VandenBerg and Cooper, Reference VandenBerg and Cooper1992). Thus, discovery of this fauna suggests the presence of an interval, here referred to the Diplacanthograptus geniculatus-Orthograptus quadrimucronatus beds, in the upper Tianzhu and lower Sijiagou formations, between the Amplexograptus maxwelli and Anticostia macgregorae beds, which could roughly correspond to the Ka1–3 intervals.

Anticostia macgregorae beds

The present biounit includes a low-diversity graptolite fauna that is dominated by the eponymous species, Anticostia macgregorae Stewart and Mitchell, Reference Stewart and Mitchell1997, and Anticostia tenuissima (Ross and Berry, Reference Ross and Berry1963). This assemblage occurs in the upper Sijiagou Formation (SB2, SD4 and SD2) in the Sijiagou section (Figs. 1, 2). Anticostia macgregorae was first described from the Amplexograptus prominens Biozone (Richmondian, corresponding partially to the conodont Amorphognathus ordovicicus Biozone) from the Vauréal Formation of the Anticosti Island (Stewart and Mitchell, Reference Stewart and Mitchell1997). It is also present in the upper D. complanatus Biozone of Scotland (Williams, Reference Williams1987), and the Appendispinograptus supernus Biozone of Siberia (Koren’ et al., Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983). Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) reported material of Anticostia macgregorae from the Paraorthograptus pacificus Biozone in Nevada. In China, it occurs in the D. complanatus Biozone at Yakeruike, near the Wushi County in the western margin of the Tarim Platform (Chen et al., Reference Chen, Zhang, Li, Fan, Tang, Chen and Zhang2012). Another anticostid, Anticostia tenuissima occurs from the Orthograptus quadrimucronatus Biozone of the Hanson Creek Formation in Nevada (Ross and Berry, Reference Ross and Berry1963) and ranges upward into the Dicellograptus ornatus Biozone (Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011). At the location of USGS D474c (1.5 mi [2.4 km] from the north end of Martin Ridge, Nevada, USA), it associated with Climacograptus hastatus (Ross and Berry, Reference Ross and Berry1963). The latter is recognized as a common species in the early Ashgill or Ka4 elsewhere and is widely distributed in the Wufeng Formation of the Yangtze Platform region of China (Mu et al., Reference Mu, Li, Ge, Chen, Lin and Ni1993; Chen et al., Reference Chen, Rong, Mitchell, Harper, Fan, Zhan, Zhang, Li and Wang2000b). Mitchell et al. (Reference Mitchell, Goldman, Cone, Maletz and Janousek2003) reported Anticostia macgregorae and Anticostia fastigata (Davies, Reference Davies1929) from the Ea4, D. gravis Biozone (= P. linearis Biozone) in the Phi Kappa Formation of Idaho. Thus, the suite of anticostids reported herein indicates an age equivalent to that of the P. linearis to the D. complanatus biozones.

The diversity of the graptolite fauna from the D. complanatus Biozone in the world is usually low (Elles and Wood, Reference Elles and Wood1904, Reference Elles and Wood1906, Reference Elles and Wood1907; Davies, Reference Davies1929; Berry, Reference Berry1960; Ross and Berry, Reference Ross and Berry1963; Toghill, Reference Toghill1970; Koren’ et al., Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983; Williams, Reference Williams1987; VandenBerg and Cooper, Reference VandenBerg and Cooper1992; Mu et al., Reference Mu, Li, Ge, Chen, Lin and Ni1993; Zalasiewicz et al., Reference Zalasiewicz, Taylor, Rushton, Loydell, Rickards and Williams2009). The Anticostia macgregorae beds in the present study bear a graptolite fauna of particularly low diversity, suggesting that it might come from this interval, although the low diversity of the Anticostia macgregorae beds might also reflect sampling bias in this remote and difficult region.

Appendispinograptus longispinus Biozone

Exposures of the Xiehao Formation in the West and East Qiqiaogou sections, as well as Zhigou, which is an isolated locality between Sijiagou and Qiqiaogou near Xiehao (Figs. 1, 2) provide the bulk of the collections assigned to this biozone. These strata produce the richest and most diverse assemblage of graptolites discovered from the Katian strata in the study area with a total of eight genera and 15 species. The fauna is dominated by climacograptids of the genera Appendispinograptus Li and Li, Reference Li and Li1985, Climacograptus? Hall, Reference Hall1865, Styracograptus Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011, and Alulagraptus new genus. Among the fauna from this interval, there are again several endemic species, e.g., Alulagraptus ensiformis (Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963), Climacograptus? papilio Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963, and Dicellograptus sinicus Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963, but the majority are widely shared with the late Katian, paleotropical faunas elsewhere (Table 1). Most of these shared species have their first appearance within the D. complexus Biozone of South China (Chen et al., Reference Chen, Rong, Mitchell, Harper, Fan, Zhan, Zhang, Li and Wang2000b, Reference Chen, Fan, Melchin and Mitchell2005) or its equivalents: the lower part of the A. supernus Biozone in Kazakhstan (Koren’ et al., Reference Koren’, Mikhaylova, Tsay, Apollonov, Bandaletov and Nikitin1980) and Siberia (Koren’ et al., Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983), the Bo2 in Australasia (VandenBerg and Cooper, Reference VandenBerg and Cooper1992), the D. ornatus Biozone in North America (Carter and Churkin, Reference Carter and Churkin1977; Melchin, Reference Melchin1987; Mitchell et al., Reference Mitchell, Goldman, Cone, Maletz and Janousek2003; Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011; Loxton, Reference Loxton2017) and the lower part of the Dicellograptus anceps Biozone in Scotland (Williams, Reference Williams1982; Zalasiewicz et al., Reference Zalasiewicz, Taylor, Rushton, Loydell, Rickards and Williams2009). This group of species generally ranges upward into the latest Katian or Hirnantian strata (Chen et al., Reference Chen, Rong, Mitchell, Harper, Fan, Zhan, Zhang, Li and Wang2000b, Reference Chen, Fan, Melchin and Mitchell2005; Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011). In contrast, Dicellograptus complanatus and Anticostia thorsteinssoni (Melchin, Reference Melchin1987), which here appear in collections Sh10-2 and Sh13, respectively (Fig. 2), elsewhere have their last appearances in the lower parts of the A. supernus and D. anceps biozones (Bo2), whereas Paraorthograptus kimi (Koren’, Reference Koren’1979) (collection Sh5, Fig. 2) first appears in their upper part (Bo3) together with the more widely reported and closely related Paraorthograptus pacificus (Ruedemann, Reference Ruedemann1947) (Koren’ et al., Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983; Loxton, Reference Loxton2017). These relationships indicate that the Xiehao Formation collections most likely represent some part of the D. complexus to P. pacificus biozones. Given the relatively limited occurrences in the present collections of taxa restricted to one or the other of these biozones, we treat these latest Katian collections as a whole and refer them to a combined A. longispinus Biozone, which correlates closely with the similarly inclusive A. supernus and D. anceps biozones in their respective regions (Koren’ et al., Reference Koren’, Mikhaylova, Tsay, Apollonov, Bandaletov and Nikitin1980, Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983; Williams, Reference Williams1982; Loydell, Reference Loydell2012).

Table 1.

Occurrences of graptolite species in the Appendispinograptus longispinus Biozone. BR = Blackstone River section (Loxton, Reference Loxton2017); EQ = East Qilianshan (this paper); KL = Kolyma (Koren’ et al., Reference Koren’, Sobolevskaya, Mikhaylova and Tsai1979); NV = Nevada (Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011); SK = southern Kazakhstan (Koren’ et al., Reference Koren’, Mikhaylova, Tsay, Apollonov, Bandaletov and Nikitin1980); YR = Yangtze region (Chen et al., Reference Chen, Rong, Mitchell, Harper, Fan, Zhan, Zhang, Li and Wang2000b).

Type species

Didymograptus elegans Carruthers, Reference Carruthers1867.

Type specimen

Lectotype, BU 1072b, upper Hartfell shales, Dob's Linn, Scotland (Elles and Wood, Reference Elles and Wood1904, pl. 20, fig. 1b), selected by Toghill (Reference Toghill1970, p. 13).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Remarks

Only the proximal part of the tubarium is preserved in the present specimen. It agrees with the type specimens in general characters. However, the thecal spacing of the present form is slightly closer than in the type specimens described by Elles and Wood (Reference Elles and Wood1904).

Dicellograptus cf. D. complanatus Lapworth, Reference Lapworth1880
Figures 3.5, 4.6

cf. 1880

Dicellograptus complanatus Lapworth, p. 160, pl. 5, fig. 17a–c.

Figure 3.

Line drawings. (1, 2, 6) Dicellograptus minor Toghill, Reference Toghill1970: (1) NIGP 11658 (Sh10-1); (2) NIGP 11654 (Sh10); (6) NIGP 11655 (Sh10-1). (3, 4, 7) Dicellograptus sinicus Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963: (3) NIGP 11649 (Sh12); (4) NIGP 11650 (Sh3); (7) NIGP 11648 (Sh12). (5) Dicellograptus cf. D. complanatus Lapworth, Reference Lapworth1880, NIGP 11660 (Sh5). (8) Dicellograptus cf. D. sinicus Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982, NIGP 11651 (Sh12). Scale bars = 1 mm.

Figure 4.

Line drawings. (1, 12) Anticostia lata (Elles and Wood, Reference Elles and Wood1906): (1) NIGP 11717 (Sh6); (12) NIGP 11679 (Sh14). (2, 4) Paraorthograptus kimi (Koren’, Reference Koren’1979): (2) NIGP 11901 (Sh5); (4) NIGP 11902 (Sh5). (3) Anticostia macgregorae Stewart and Mitchell, Reference Stewart and Mitchell1997, NIGP 11699 (SD4). (5) Amplexograptus maxwelli (Decker, Reference Decker1935), NIGP 11716 (Sh1). (6) Dicellograptus cf. D. complanatus Lapworth, Reference Lapworth1880, NIGP 11661a (Sh24), upper Sijiagou Formation, Zhigou. (7, 8, 10) Dicellograptus sinicus Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963: (7) NIGP 11652 (Sh12); (8) NIGP 11646 (Sh12); (10) holotype, NIGP 11647 (Sh12). (9) Anticostia tenuissima (Ross and Berry, Reference Ross and Berry1963), NIGP 11694a (SD2). (11) Dicellograptus complanatus Lapworth, Reference Lapworth1880, NIGP 11645 (Sh10-2). (13, 14) Anticostia teres? (Perner, Reference Perner1895): (13) NIGP 11696 (SB2); (14) NIGP 11697 (SB2). Scale bars = 1 mm.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West Qiqiaogou section and upper Sijiagou Formation at Zhigou.

Remarks

The specimens differ from those of Dicellograptus complanatus in having a narrower stipe (Dicellograptus complanatus: 0.36–0.50 mm; Dicellograptus cf. D. complanatus: 0.18–0.45 mm).

Holotype

SM A19333, upper Hartfell shales, Dob's Linn, Scotland (Elles and Wood, Reference Elles and Wood1904, pl. 20, fig. 2c), selected by Toghill (Reference Toghill1970, p. 16).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Remarks

Although the details of thecae are not well preserved, the general characters of the tubarium agree with those of the type specimens.

Holotype

NIGP 11647 (Figs. 4.10, 13.1), originally illustrated by Mu et al. (Reference Mu, Li, Ge, Chen and Zhang1963, p. 57, pl. 23, fig. 4), not NIGP 11649 selected by Mu et al. (Reference Mu, Song, Li, Xu and Zhang1982).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West and East Qiqiaogou sections.

Description

Tubarium consisting of two reclined stipes. First thecal pair diverging from the sicula horizontally, turning upward abruptly at their apertural parts, with long subapertural spines, reaching a length of 3.6 mm. Subsequent three thecal pairs possessing subapertural spines as well. However, some of the subapertural spines on the subsequent thecae located a short distance from the thecal apertures as a result of the different preservation. Sicula long and slender, 2.2 mm long; aperture 0.2 mm wide with a short virgella. First theca arising from the middle metasicula and extending downward along the sicula, turning outward near the aperture of the sicula. Proximal parts of two stipes each strongly upwardly arching and becoming parallel with each other in the mesial part (from roughly the third theca to the seventh to tenth thecae) after which becoming ventrally flexed and ranging from divergent to recurved. Stipes appearing to have been loosely helically coiled, and thus some of the variance in timing and degree of divergence could be a preservational artefact. Stipe width increasing considerably over the proximal to mesial portions of the stipes, from 0.4 mm at the aperture of th1¹ to 0.6 mm at th4¹ in the holotype. However, other specimens (e.g., NIGP 11646; Fig. 4.8), exhibiting a more dramatic change of the width, from 0.4 mm at the aperture of th1¹ to 0.75 mm at th5¹. Increasing width in the proximal stipes reflecting the increasing width of the thecae themselves, which is accompanied by a greater inclination of the infragenicular walls and a more strongly introtorted supragenicular region. Stipe widths decreasing to ~0.5 mm on average as the stipes diverge outward and supragenicular walls become nearly parallel to the stipe axis with slightly isolated apertures. 2TRD₂ = 1.00–1.63 mm; 2TRD₅ = 1.27–1.91 mm; 2TRD₁₀ = 1.45–2.81 mm.

Remarks

The present form resembles Dicellograptus elegans in the shape of the stipes (particularly their proximally parallel to distally more divergent to recurved form), the long and slender sicula, and the long subapertural spines on the first pair of thecae. However, Dicellograptus elegans lacks the zone of expanded stipe widths and subapertural spines present proximally in Dicellograptus sinicus. Additionally, the thecae are slightly more widely spaced in the present species. The present form also resembles Dicellograptus turgidus Mu, Reference Mu1963a in the general shape of the tubarium. However, it again differs from the latter in having well-developed subapertural spines from the second to fourth pairs of thecae.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Remarks

Compared to Dicellograptus sinicus, the specimen is characterized by more closely spaced stipes in the proximal parts, with closer thecal spacing (9 thecae in the first 5 mm).

Type species

Diplograptus perexcavatus Lapworth, Reference Lapworth1876.

Amplexograptus maxwelli (Decker, Reference Decker1935)
Figures 4.5, 5.6–5.8, 6.5, 6.7, 7.11, 14.5, 14.6, 14.10

Reference Decker1935

Diplograptus (Amplexograptus) maxwelli Decker, p. 242, pl. 1, figs. 1–7, 1a–6a.

Reference Mu1963b

Amplexograptus disjunctus Mu and Zhang; Mu, p. 360, fig. 7b–d (nomen nudum).

Reference Mu1963b

Amplexograptus gansuensis Mu and Zhang; Mu, p. 360, fig. 7a (nomen nudum).

Reference Mu, Song, Li, Xu and Zhang1982

Amplexograptus disjunctus Mu and Zhang in Mu et al., p. 322, pl. 78, figs. 32, 33.

Reference Mu, Song, Li, Xu and Zhang1982

Amplexograptus gansuensis Mu and Zhang in Mu et al., p. 321, pl. 78, figs. 30, 31.

Reference Chen, Rong, Mitchell, Harper, Fan, Zhan, Zhang, Li and Wang2000b

Amplexograptus maxwelli maxwelli; Chen et al., p. 290, figs. 5.19, 5.27, 7.16, 7.22, 9.8 (with 11 references in synonymy).

Reference Goldman, Campbell and Rahl2002

Amplexograptus maxwelli; Goldman et al., p. 925, figs. 3.11–3.16, 4.2, 4.4–4.6 (with six references in synonymy).

Reference Mu, Li, Ge, Lin and Ni2002

Amplexograptus gansuensis; Mu et al., p. 529, pl. 152, figs. 16, 17.

Figure 5.

Line drawings. (1, 3, 9) Anticostia macgregorae Stewart and Mitchell, Reference Stewart and Mitchell1997: (1) NIGP 11698 (SD4); (3) NIGP 11704 (Sh13); (9) NIGP 11702 (SD4). (2) Anticostia thorsteinssoni (Melchin, Reference Melchin1987), NIGP 11703 (Sh13). (4, 5) Rectograptus abbreviatus (Elles and Wood, Reference Elles and Wood1907): (4) NIGP 11783 (Sh10-1); (5) NIGP 11670 (Sh5). (6–8) Amplexograptus maxwelli (Decker, Reference Decker1935): (6) NIGP 11722 (Sh1); (7) NIGP 11723 (Sh1); (8) NIGP 11719 (SC3). Scale bars = 1 mm.

Figure 6.

Line drawings. (1–3) Anticostia lata (Elles and Wood, Reference Elles and Wood1906): (1) NIGP 11659 (Sh5); (2) NIGP 11831 (Sh11); (3) NIGP 11760 (Sh11). (4, 6, 8–10) Pseudoclimacograptus tianzhuensis Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982: (4) NIGP 11891 (SC1); (6) NIGP 11888 (Sh1); (8) NIGP 11885 (SC1); (9) NIGP 11884 (SC1); (10) NIGP 11896 (SC3). (5, 7) Amplexograptus maxwelli (Decker, Reference Decker1935): (5) NIGP 11715 (Sh1); (7) NIGP 11711 (Sh1). Scale bars = 1 mm.

Figure 7.

Line drawings. (1–8) Climacograptus? papilio Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963: (1) NIGP 11802 (Sh10-1); (2) neotype, NIGP 11791 (Sh10-1); (3) NIGP 11785 (Sh10-1); (4) NIGP 11795 (Sh10); (5) NIGP 11779 (Sh10); (6) NIGP 11784b (Sh10-1); (7) NIGP 11781 (Sh13); (8) NIGP 11786 (Sh10). (9, 10) Pseudoclimacograptus tianzhuensis Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982; (9) NIGP 11883 (SC2); (10) NIGP 11882 (SC2). (11) Amplexograptus maxwelli (Decker, Reference Decker1935), NIGP 11712b (Sh1). Scale bars = 1 mm.

Type specimens

Syntypes (7), west of Nebo Store, OMNH A2041; and A2042–A2047, Rock Crossing, Criner Hills, Oklahoma, USA (Decker, Reference Decker1935, pl. 1, figs. 1–7, 1a–6a).

Occurrence

Amplexograptus maxwelli beds, Tianzhu Formation at the Sijiagou and West Qiqiaogou sections.

Description

Tubarium small with a length of 13 mm and a uniform distal width of 1.4–1.6 mm. Sicular aperture 0.17 mm wide with a short virgella (Fig. 7.11) and antivirgellar spines (Fig. 5.8). Th1¹ extending downward from its origin in the middle part of the sicula and turning outward and upward at the base of the virgella, whereas the ventral wall of th1² is only slightly inclined from the colony axis, forming an asymmetrical proximal end of the tubarium. Thecae of typical amplexograptid form with straight and parallel to slightly inclined supragenicular walls, conspicuous genicular flanges (mesial flanges; Riva, Reference Riva1987), and apertural lappets (Figs. 4.5, 14.10; which commonly causes the thecal apertures of flattened specimens to appear slightly introverted). Infragenicular walls dorsally curved and indicating an alternate arrangement of thecae. Thus, tubaria of the present species aseptate with only a free nema in the middle of the tubarium, consistent with the very delayed insertion of a median septum exhibited by the type material (Riva, Reference Riva1987). 2TRD₂ = 1.10–1.25 mm; 2TRD₅ = 1.25–1.40 mm; 2TRD₁₀ = 1.4–1.5 mm.

Remarks

Some of the present specimens possess prominent genicular flanges (Figs. 4.5, 5.6, 7.11), however almost all of the specimens are rather flattened and many are mildly distorted. Consequently, we are uncertain whether they all belong to Amplexograptus maxwelli maxwelli or whether some could represent Amplexograptus maxwelli spinosus Chen et al., Reference Chen, Ni, Mitchell, Qiao and Zhan2000a.

Type species

Anticostia macgregorae Stewart and Mitchell, Reference Stewart and Mitchell1997

Type specimen

Lectotype, SM A19680, upper Hartfell shales, Dob's Linn, Scotland (Elles and Wood, Reference Elles and Wood1906, pl. 27, fig. 3a), selected by Riva (Reference Riva1988, p. 228).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West and East Qiqiaogou sections.

Remarks

The present species has been described by many authors. Among the features visible in flattened material, Anticostia lata differs from Amplexograptus maxwelli in having more prominent genicular flanges, more weakly inclined supragenicular walls, and a considerable length above its point of upward turning in th1¹, which is also more strongly upwardly grown. In addition, Anticostia lata also widens much more gradually and has a greater distal width than Amplexograptus maxwelli.

Holotype

GSC 115740, Tower Member of Vauréal Formation, Anticosti Island, Canada (Stewart and Mitchell, Reference Stewart and Mitchell1997, fig. 5A, B).

Occurrence

Anticostia macgregorae beds, upper Sijiagou Formation at the Sijiagou section and A. longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Description

Tubarium ~20 mm long, 0.9 mm wide proximally (but is slightly narrower at the second pair of thecae than at the first), gradually increasing distally to a maximum of ~1.8 mm. First theca (th1¹) growing outward and upward for a considerable distance from the sicula. Unfortunately, present material does not show the growth of the protheca of th1² and its crossing cannel th1¹ even in their uncompressed specimens. Virgella and antivirgellar spine well developed. Tubarium aseptate. Thecae generally glyptograptid in form but with slightly introverted apertures produced by conspicuous apertural cusps. 2TRD₂ = 1.70–1.75 mm; 2TRD₅ = 1.72–1.75 mm; 2TRD₁₀ = 1.85–1.90 mm; 2TRD_dist = 2.00–2.10 mm in a few specimens.

Remarks

The present specimens possess most of the characters described by Stewart and Mitchell (Reference Stewart and Mitchell1997) based on their type specimens. However, one specimen (Fig. 5.3) differs from the type specimens in having more widely spaced thecae (10 thecae in 10 mm).

Holotype

USNM 138685, Hanson Creek Formation, northern end of Martin Ridge, Nevada, USA (Ross and Berry, Reference Ross and Berry1963, pl. 11, fig. 6).

Occurrence

Anticostia macgregorae beds, upper Sijiagou Formation at the Sijiagou section.

Description

Tubarium length to at least 5 mm; proximal width 0.75 mm, increasing gradually to 1.2 mm at the sixth thecal pair. Mesial spine occuring on th1¹. Thecae all elongated with sigmoid ventral walls, alternately arranged in the aseptate tubarium. 2TRD₂ ~1.3 mm; 2TRD₅ = 1.6 mm.

Remarks

The present specimen conforms well with the characteristically short first thecae, close thecal spacing, and bluntly rounded geniculae, and the usual anticostid tubarium construction. Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) provided detailed comparisons among the contemporaneous species.

Type material

Lectotype, NM L27529, Lejškov, Czech Republic (Perner, Reference Perner1895, pl. 8, fig. 13a, b), refigured by Přibyl (Reference Přibyl1949, pl. 2, fig. 12) and Kraft et al. (Reference Kraft, Štorch and Mitchell2015, fig. 5E), designated by Přibyl (Reference Přibyl1949).

Occurrence

Anticostia macgregorae beds, upper Sijiagou Formation at the Sijiagou section.

Description

Tubarium length to at least 10 mm; proximal width 1.1 mm, increasing gradually to 1.66 mm at the fifth thecal pair, then remaining uniform. Sicula bearing a short, straight virgella; antivirgellar spines not preserved. Th1¹ turning upward at ~0.25 mm below the sicular aperture and is broadly arched. Th1² completely covering the sicula in reverse view, turning upward just above the turning point of the th1¹. A subapertural spine occuring on both th1¹ and th1². Thecae all elongated with sigmoid ventral walls, prominent apertural cusps, and alternately arranged in the aseptate tubarium. 2TRD₂ = 1.50–1.75 mm; 2TRD₅ = 2.0 and uniform thereafter.

Remarks

The type specimen of Anticostia teres is a fragment. The present specimens agree with those described by Kraft et al. (Reference Kraft, Štorch and Mitchell2015) in both form and dimensions. The specimens from the Czech Republic probably occur in rocks that are coeval with the P. linearis Biozone of the British succession and have not previously been discovered outside of Perunica and Baltica (Kraft et al., Reference Kraft, Štorch and Mitchell2015). Thus, we designate the present specimens as Anticostia teres?, pending discovery of further material.

Holotype

GSC 78409, Truro Island, Canada at 12.0 m (Melchin, Reference Melchin1987, pl. 2, fig. 8).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Remarks

Tubaria of this species of Anticostia has relatively straight and weakly inclined thecae as well as prominent proximal spines (virgella, antivirgellar spines, and th1¹ mesial spine). The present specimen resembles the type specimens and others described by Goldman et al. (Reference Goldman, Bergström and Mitchell1995) and Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) in their characteristic features, however, the present specimen is slightly wider across the first thecal pair than the type material (1.3 mm rather than 0.9–1.2 mm). Because the species is known from relatively few specimens, however, its dimensional ranges are not well established. The stratigraphic range of this species also is not well established, although all reported occurrences are from equivalents of the D. ornatus Biozone.

Type species

Graptolithus quadrimucronatus Hall, Reference Hall1865.

Type specimen

Syntypes (3), GSC 1898a, b, d, Utica shale, Lake St. John, Quebec, Canada (Hall, Reference Hall1865, pl. 13, fig. 1–7), listed by Bolton (Reference Bolton1960, p. 104).

Occurrence

Diplacanthograptus geniculatus-Orthograptus quadrimucronatus beds, lower Sijiagou Formation at the Sijiagou section.

Remarks

The present materials agree with the type specimens, which were restudied by Goldman (Reference Goldman1995). The material at hand presents several different preservational aspects, as is common for this species. From the subscalariform and biprofile specimens (Fig. 13.5, 13.10, respectively), the prominent apertural spines, virgella, and antivirgellar spines as well as an asymmetrical first pair of thecae are clearly visible. These features are consistent with the astogenetic pattern G structure expected for colonies of this species, although because they are flattened specimens, the detailed features of this proximal structure are not evident.

Orthograptus quadrimucronatus occurs from the Corynoides americanus through the Amplexograptus manitoulinensis biozones in North America (Goldman, Reference Goldman1995). Indeed, the species is common in the early Katian strata throughout much of the paleotropics, as discussed above. The occurrence of the present form in East Qilianshan could imply an equivalent sinterval between the Amplexograptus maxwelli and Anticostia macgregorae beds.

Type species

Pararetiograptus sinensis Mu in Mu et al., Reference Mu, Li, Ge, Chen, Ni, Lin and Mu1974

Remarks

The first graptolites referable to Pararetiograptus were described by Mu (Reference Mu1963b) and Mu et al. (Reference Mu, Li, Ge, Chen and Zhang1963) based on material from Qilianshan. In the recent revision of Pararetiograptus, Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) based their choice of the proper spelling of this name on the usage by Mu (Reference Mu1974, p. 233), who referred to the taxon as ‘Parareteograptus nov.,’ and stated briefly how tubaria in this taxon differed in form from those of Reteograptus Hall, Reference Hall and Hall1859. Mu (Reference Mu1974) also gave the same taxon a new name ‘Pararetiograptus (gen. nov.)’ in his later publication (Mu et al., Reference Mu, Li, Ge, Chen, Ni, Lin and Mu1974, p. 163). In this publication, the authors provided a more detailed description of ‘Pararetiograptus,’ as well as description and illustration of ‘Pararetiograptus sinensis, (gen. et sp. nov.),’ which the authors selected as the type species.

Similarly, Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) attributed authorship of Retiograptus grandis var. uniformis to Mu and Zhang in Mu, Reference Mu1963b, which, as a consequence, they considered to be a nomen nudum that was first made available by Mu and Lin (Reference Mu and Lin1984). On the basis of these supposed dates of priority and their similarity in form, Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) considered Pararetiograptus uniformis (Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963) to be a junior synonym of Pararetiograptus sinensis. In fact, the opposite appears to be the case. Mu (Reference Mu1963b) indeed illustrated this species without description, but the species was described formally in the later publication (Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963), a fact of which Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011) were unaware. Thus, the Qilianshan taxon, Pararetiograptus uniformis, is the senior name for Pararetiograptus sinensis.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West and East Qiqiaogou sections.

Description

Tubarium length to at least 43 mm, with a width of 1.3 mm at the proximal end, increasing rapidly to a maximum width of 4.0 mm, and generally maintained thereafter. Proximal end exhibiting a stout, short virgella, enlarged antivirgellar spines, and a prominent apertural spine on th1¹. Thecal apertures nearly horizontal, consisting of an apertural ring that is linked to paired ventral lists. Tubarium aseptate. Relatively short, strongly inclined thecae bearing arched dorsal lists located approximately at the boundary between successive alternating thecae, giving the impression of a strongly zigzaged median strand. Dorsal lists uniting with the ventral lists and apertural lists at the dorsal margin of the thecal aperture and are nearly parallel to the ventral lists. Thus, lists forming a nearly pentagonal thecal framework. 2TRD₂ = 1.0–1.2 mm; 2TRD₅ = 1.1–1.4 mm; 2TRD₁₀ = 1.25–1.50 mm; 2TRD_dist = 1.55–1.80 mm.

Remarks

Tubaria assigned to this form strongly resemble those of other species referred to Pararetiograptus in the configuration of the lists and reduction in thickness of the thecal walls. The present material is remarkable for its great width combined with unusually closely spaced thecae. The specimens are markedly wider than those referred to Pararetiograptus magnus Mu in Mu et al., Reference Mu, Li, Ge, Chen, Ni, Lin and Mu1974 and yet have much more closely spaced thecae, which in general could be caused by tectonic deformation but does not appear to be so in this case. Mu (Reference Mu1963b) and Mu et al. (Reference Mu, Li, Ge, Chen and Zhang1963) referred these Qilianshan specimens to Reteograptus grandis Ruedemann, Reference Ruedemann1947, with which they agree in their dimensions (including the relatively closeness of thecal spacing compared to colony width) and general colony form. Ross and Berry (Reference Ross and Berry1963) transferred Ruedemann's species to Orthograptus. The type material of O. grandis is deformed and metamorphosed, which makes determination of its precise structure difficult, but restudy of the types and additional material from the Phi Kappa Formation in Idaho by one of us (CEM) suggests that the species likely has paired apertural spines on the proximal thecae and might be a gigantic member of the O. quadrimucronatus species group, similar to O. eucharis (Hall, Reference Hall1865) (see Herr, Reference Herr1971; Goldman and Bergström, Reference Goldman and Bergström1997) and O. pulcherrimus (Keble and Harris, Reference Keble and Harris1934) (see VandenBerg and Cooper, Reference VandenBerg and Cooper1992), both of which have a similar thecal structure and also were placed by their original authors in Retiograptus. The present material, however, does not appear to possess paired thecal spines and has a thecal structure more consistent with that of species of Pararetiograptus than with O. grandis. Further work is required to accurately determine these relationships and so we leave the present material in open nomenclature.

One ~25 mm long distal fragment (Fig. 19.9) has an overall nearly uniform maximum width (4.4–4.8 mm) and thecal spacing, but exhibits three narrower zones spaced at ~7 mm intervals. This feature suggests some source of growth periodicity affected this large colony.

Type species

Climacograptus innotatus var. pacificus Ruedemann, Reference Ruedemann1947.

Holotype

TsGM 1/11565, middle of the Chashmankolonian beds, Shakhriomon-2 Pass, Zeravshan-Gissar mountainous region, Uzbekistan (Koren’, Reference Koren’1979, fig. 2b).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West Qiqiaogou section.

Description

Tubarium length to at least 11 mm, with a width of 0.7 mm proximally and increasing gradually to a maximum width of 1.4–1.5 mm distally. Sicula and very proximal portion broken off. Thecae inclined and geniculate with straight and slightly everted apertural margins, nearly parallel supragenicular walls, oblique infragenicular walls, and genicular spines. Thecae alternately arranged throughout the aseptate tubarium. A straight nema visible within the distal portion of the tubarium. 2TRD_dist = 1.67 mm.

Remarks

The present material agrees with the holotype (Koren’, Reference Koren’1979, pl. 8, fig. 2b) and the specimens described by Loxton (Reference Loxton2017) in all characters. It differs from Paraorthograptus pacificus in having a narrow and relatively uniform width.

Type species

Diplograptus pristis var. truncatus Lapworth, Reference Lapworth1877.

Holotype

BU 1248, upper Hartfell shales, Dob's Linn, Scotland (Elles and Wood, Reference Elles and Wood1907, pl. 29, fig. 6a).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation, at the West and East Qiqiaogou sections.

Remarks

The present specimens agree with the type materials in all characters, especially with the illustrations of Elles and Wood (Reference Elles and Wood1907, pl. 29, fig. 6a, e). Chen et al. (Reference Chen, Fan, Melchin and Mitchell2005) recorded this taxon from the Yangtze region where it first appears in the D. complexus Biozone and ranges upward through the late Katian. This species also occurs uncommonly in the early Hirnantian strata in the Yangtze region (Chen et al., Reference Chen, Fan, Melchin and Mitchell2005), Nevada (Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011), and Scotland (Melchin et al., Reference Melchin, Holmden and Williams2003). The occurrence of the present form in East Qilianshan could coincide with its peak occurrence in the Katian of the Yangtze region.

Type species

Climacograptus uncinatus Keble and Harris, Reference Keble and Harris1934, which has recently been reillustrated by VandenBerg (Reference VandenBerg, Wilkinson, Zalasiewicz, Rushton and Muir2018), who selected NMV P14401 as the lectotype.

Diagnosis

Climacograptid with a single pair of septal spines extending outward from the nema and passing through the obverse and reverse sides of the tubarium in the proximal part of the colony. Septal spines can bear vane-like appendages. Sharply geniculate thecae exhibiting ventral margins that are nearly parallel to the tubarium axis and possess simple apertures reinforced by complete apertural selvages. Tubarium with a complete median septum that includes crossbar lists that link the lateral tubarium walls to the nema. Proximal end of tubarium rounded and bearing a virgella but no thecal or other sicular spines.

Etymology

Alula is derived from Latin, indicating a small wing-like structure.

Remarks

Spines and appendages in many biserial graptoloids are usually derived from the lateral side of the tubarium, i.e., from the ventral walls of thecae. In addition to these thecal spines, many Lasiograptidae (sensu Mitchell et al., Reference Mitchell, Goldman, Klosterman, Maletz, Sheets and Melchin2007b) also produce long spines that arise at regular intervals from the nema and extend from the obverse and reverse sides of the tubarium along the median septum (e.g., Elles and Wood, Reference Elles and Wood1908; Mitchell, Reference Mitchell1988; Bates and Kirk, Reference Bates and Kirk1991; Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011; Maletz et al., Reference Maletz, Bates, Brussa, Cooper, Lenz, Riva, Toro and Zhang2014). Reflecting the location of these structures along the median septum, Elles and Wood (Reference Elles and Wood1908) referred to these spines as ‘septal process’ and noted that these spines often bear broad paddle-like processes referred to as scopulae. Paired scopulae occur commonly in, e.g., Hallograptus bimucronatus (Nicholson, Reference Nicholson1869) (see Ruedemann, Reference Ruedemann1947, pl. 81, figs. 12–14) and Neurograptus fibratus (Lapworth, Reference Lapworth1876) (see Elles and Wood, Reference Elles and Wood1908, p. 332, fig. 218) where they are clearly built upon ramifying spines that were embedded within the median septum and extend outward symmetrically from the nema. Broadly similar spines, also spaced at intervals along the lateral walls, are present Glossograptus holmi Bulman, Reference Bulman1931 as well (Whittington and Rickards, Reference Whittington and Rickards1969), although presumably these evolved independently. Keble and Harris (Reference Keble and Harris1934) described a new species, Climacograptus uncinatus, which presents another independently derived instance of similar paired spines extending from the lateral walls of the tubarium. Alulagraptus ensiformis presents a further elaboration of this structure. Both species are primarily preserved in scalariform view as a consequence of these septal spines. Keble and Harris (Reference Keble and Harris1934, p. 173) inferred that the spines “probably prevent the tubarium coming to rest except with the thecal apertures at right angles to the bedding surface.” This form of preservation obscures the thecal characters of most specimens of Alulagraptus n. gen., however, the paralectotype specimen of Alulagraptus uncinatus, which is preserved in subscalariform view (NMV P14379; Keble and Harris, Reference Keble and Harris1934; VandenBerg, Reference VandenBerg, Wilkinson, Zalasiewicz, Rushton and Muir2018), as well as specimens from the Alulagraptus uncinatus Biozone in the Phi Kappa Formation of Idaho (Carter, Reference Carter1972; Carter and Churkin, Reference Carter and Churkin1977; Mitchell et al., Reference Mitchell, Goldman, Cone, Maletz and Janousek2003), reveal that Alulagraptus uncinatus exhibits sharply geniculate thecae with short, weakly inclined ventral walls and apertures that are reinforced by a thin apertural selvage (see Fig. 18.4).

Some details of the proximal structure of Alulagraptus n. gen. can also be discerned from the available material. The sicula of Alulagraptus uncinatus, like those in species of Styracograptus, appears to lack a prosicula and the nema attaches directly to the distal (aboral) margin of the metasicula (Fig. 18.2–18.4). The nema subsequently divides distally of the growing edge of the Alulagraptus uncinatus tubarium into a Y-shaped structure that the colony eventually grows around at the level of the third or fourth thecal pair (Thomas, Reference Thomas1960, pl. 11, fig. 156). The septal spines in Alulagraptus ensiformis occur in a similar location and can also arise from the nema, but unlike Alulagraptus uncinatus, these spines appear not to be a result of a terminal bifurcation of the nema because the nema is visibly present in the distal parts of the tubaria of Alulagraptus ensiformis (Figs. 10, 17). As in other climacograptids, the nema in both species is supported by crossbar lists that form at the base of each of the successive dorsal walls that form a median septum in these graptolites (Figs. 10.3, 17.2–17.5; see Goldman et al., Reference Goldman, Mitchell, Melchin, Fan, Wu and Sheets2011 for further discussion). Several Phi Kappa slabs that bear numerous mature tubaria of Alulagraptus uncinatus also contain growth stages that are consistent in size and shape with the proximal end of the more mature specimens and that suggest a Pattern D primordial astogeny (sensu Mitchell, Reference Mitchell1987) and that match the dimensions of the certain specimens of Alulagraptus uncinatus, however, this interval in the Phi Kappa Formation also includes specimens of Styracograptus tubuliferus (Lapworth, Reference Lapworth1876), which also have this proximal structure and not entirely dissimilar sicular dimensions. Consequently, many details of the primordial astogeny remain uncertain. Nevertheless, the available information is sufficient to indicate that this small clade likely descended from a species of Styracograptus.

Holotype

NIGP 11749 (Figs. 10.4, 17.3), the well-preserved specimen originally figured by Mu et al. (Reference Mu, Li, Ge, Chen and Zhang1963, pl. 23, fig. 9).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Description

All specimens in scalariform view; length to 10 mm. Open oval apertures clearly visible along the flattened ventral walls of the tubarium. Apertures 0.5–0.6 mm wide, occupying roughly half to two-thirds of tubarium width. Aperture height somewhat variable (probably owing to preservation) but mostly 0.3 mm or less. Nema straight and probably continuous throughout the tubarium. Crossbar lists connecting the nema to lateral thecal walls (arrows in Figs. 10.3, 17.2, 17.5, 20). Sicula and proximal structure of the tubarium all covered in the available scalariform specimens, leaving only a short, straight virgella visible below the proximal end. Tubarium expanding rapidly from 0.35–0.45 mm across the rounded proximal end to 0.7–0.8 mm at the level of the scopuli, beyond which most are of uniform width of 1 mm. Thecae difficult to discern in the proximal end, however, 2TRD at the level of the scopular spines ~1.1 mm. 2TRD_dist = 1.45–1.95 mm.

The most prominent character of the tubarium is the pair of appendages, which are roughly symmetrical, vane-like structures of somewhat variable size. In the younger tubaria among the present material, only scopular spines are present and, thus, it appears that the scopulate vanes develop preferentially in mature colonies. Spines appear to provide a framework that supports the scopulate vanes, which grew upward and outward from the nearly horizontal scopular spines. In several specimens, the scopulate vanes exhibit a Y-shaped, two-lobed form; furthermore, specimen NIGP 11738 (Figs. 10.7, 15.1), which lacks scopulate vanes, appears to have a branched spine on its right side with the upward limb having an orientation similar to the upper lobe of the more mature specimens. Among these more mature specimens, several (Fig. 17.1, 17.2) appear to have similarly branched spines. Because the scopulate vanes projected from the obverse and reverse sides in the proximal part of the tubarium, they leave the aperture openings free.

Remarks

Thecal form and dimensions in Alulagraptus ensiformis are very similar to those that Carter (Reference Carter1972) reported for Alulagraptus uncinatus. In addition to the presence of scopulae, Alulagraptus ensiformis differs from Alulagraptus uncinatus mainly in the configuration of the scopular spines. Those in Alulagraptus uncinatus form an upwardly divergent Y-shape structure at the apex of the nema (Thomas, Reference Thomas1960, pl. 11, fig. 156; Carter, Reference Carter1972, fig. 2J; Figs. 18.2, 18.3), which does not continue within the tubarium beyond this division point. This is a very unusual condition for axonophoran graptolites, which generally incorporate the nema into the structural framework of the thecae. Even in axonophorans in which the nema is free of these connections (as in the species of Anticostia), the nema is a universal feature of their tubaria. Nonetheless, no known specimen of Alulagraptus uncinatus exhibits a nema in the distal part of the tubarium, whereas a nema is visibly preserved in the distal part of nearly all Alulagraptus ensiformis specimens, which project horizontally from a through-going nema and can show traces of the nema at various locations distal to the scopulae. In keeping with the usual condition of axonophoran graptolites, therefore, we infer from this that the nema extended throughout the tubarium as its central axis and that scopular spines in Alulagraptus ensiformis formed as lateral branches of the nema, comparable to those in the Lasiograptidae (e.g., Orthoretiolites hami Whittington, Reference Whittington1954; well-illustrated and discussed by Bates and Kirk, Reference Bates and Kirk1991; see also discussion of this group by Štorch et al., Reference Štorch, Mitchell, Finney and Melchin2011). These structural differences in tubarium configuration combined with the presence of branched scopular spines and bilobed scopulae suggest that this present material represents a distinct species.

Type species

Climacograptus venustus Hsü, Reference Hsü1959.

Remarks

Mitchell et al. (Reference Mitchell, Chen and Finney2007a) determined that the ‘membranes’ or ribbon-like structure which grows under the lower surface of the first thecal spine pair is parasicula. This inference was further supported by Loxton et al. (Reference Loxton, Melchin, Mitchell and Senior2011). In the present specimens, parasiculae are well developed in Appendispinograptus longispinus (Hall, Reference Hall1902). Possible parathecae have also been preserved in Appendispinograptus longispinus (Figs. 8.11, 11.8).

Figure 8.

Line drawings. (1, 2, 6–8) Pseudoclimacograptus tianzhuensis Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982; (1) NIGP 11881 (Sh1); (2) holotype, NIGP 11887 (Sh1); (6) NIGP 11896-1 (SC2); (7) NIGP 11896-2 (SC2); (8) NIGP 11886 (SC1). (3–5) Climacograptus? papilio Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963: (3) NIGP 11777 (Sh10-2); (4) NIGP 11794 (Sh10); (5) NIGP 11777-1 (Sh10-1). (9–15) Appendispinograptus longispinus (Hall, Reference Hall1902): (9) NIGP 11768 (Sh3); (10) NIGP 11764 (Sh3); (11) NIGP 11763 (Sh3); (12) NIGP 11865 (Sh5); (13) NIGP 11868 (Sh9); (14) NIGP 11822 (Sh13); (15) NIGP 11766 (Sh3). Scale bars = 1 mm.

Holotype

NIGP 57374, Daduhe Formation, Hanyuan, Sichuan, China (Mu et al., Reference Mu, Li, Ge, Chen, Lin and Ni1993, pl. 36, fig. 10).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Description

Tubarium length to at least 25 mm, with a tapering proximal end. Width across the first thecal pair ~1 mm, increasing upward gradually to a maximum width of 2.4 mm at the middle to distal part of the tubarium. Virgella ~4.9 mm long, with a pair of basal spines that originates from the ventral margin of the proximalmost part of the first thecal pair. Thecae of typical climacograptid type. 2TRD₂ = 1.45 mm; 2TRD₅ = 1.81 mm; 2TRD₁₀ = 2.00 mm; 2TRD₁₅ = 2.36 mm; 2TRD₂₀ = 2.36 mm.

Remarks

Tubaria of Appendispinograptus hanyuanensis described by Ge (in Mu et al., Reference Mu, Li, Ge, Chen, Lin and Ni1993) exhibit a somewhat intermediate form between Appendispinograptus supernus (Elles and Wood, Reference Elles and Wood1906) and Appendispinograptus longispinus. Like in the former, the tubaria of Appendispinograptus hanyuanensis are relatively narrow compared to those of the latter, but have slightly longer thecae relative to colony width than either of these taxa, although less so than Appendispinograptus leptothecalis (Mu and Ge in Fu, Reference Fu1982). Also, like Appendispinograptus supernus, they appear to exhibit less torsion, which allows the distal thecae to remain in biprofile view compared to the typical subscalarifom preservation in the distal parts of the Appendispinograptus longispinus tubaria. As in the present specimen, the four type specimens of Appendispinograptus hanyuanensis all possess an elongated virgella in addition to the long basal spines on the first pair of thecae. Those specimens also appear to have a delayed median septum that begins near the tenth to twelfth pair of thecae. In contrast, Appendispinograptus supernus is aseptate throughout and Appendispinograptus longispinus tubaria become septate at approximately the eighth to tenth pair of thecae. The described specimen agrees with the type specimens in their dimensions and thecal characters, however, we cannot determine the condition of its median septum.

Appendispinograptus longispinus (Hall, Reference Hall1902)
Figures 8.9–8.15, 9, 11.2, 11.5, 11.6, 11.8, 16

Reference Hall1902

Climacograptus bicornis var. longispinus Hall, p. 54, pl. 12, figs. 8, 9.

Reference Mu1963b

Climacograptus bellulus Mu and Zhang; Mu, p. 361, fig. 10f (nomen nudum).

Reference Mu1963b

Climacograptus bicornis crassispinus Mu and Zhang; Mu, p. 361, fig. 10a (nomen nudum).

Reference Mu1963b

Climacograptus bicornis rigida Mu and Zhang; Mu, p. 361, fig. 10b (nomen nudum).

Reference Mu1963b

Climacograptus duplex Mu and Zhang; Mu, p. 361, fig. 10c (nomen nudum).

Reference Mu1963b

Climacograptus longispinus; Mu, p. 361, fig. 10d.

Reference Riva1974b

Climacograptus longispinus longispinus; Riva, p. 111, pl. 7, text-figs. 2–4 (with four references in synonymy).

Reference Koren’, Mikhaylova, Tsay, Apollonov, Bandaletov and Nikitin1980

Climacograptus longispinus hvalross Ross and Berry, Reference Ross and Berry1963; Koren’ et al., p. 134, fig. 37a–d.

Reference Mu, Song, Li, Xu and Zhang1982

Climacograptus bellulus Mu and Zhang in Mu et al., p. 318, pl. 78, figs. 8, 9.

Reference Mu, Song, Li, Xu and Zhang1982

Climacograptus bicornis crassispina Mu and Zhang in Mu et al., p. 316, pl. 77, figs. 28–29.

Reference Mu, Song, Li, Xu and Zhang1982

Climacograptus bicornis rigida Mu and Zhang in Mu et al., p. 316, pl. 78, fig. 1.

Reference Mu, Song, Li, Xu and Zhang1982

Climacograptus duplex Mu and Zhang in Mu et al., p. 318, pl. 78, figs. 10, 11.

Reference Mu, Song, Li, Xu and Zhang1982

Climacograptus longispinus; Mu et al., p. 318, pl. 78, figs. 12, 13.

Reference Yang, Ni, Li, Chen, Lin, Yu, Xia, Jiao, Fang, Ge and Mu1983

Climacograptus cf. duplex; Yang et al., p. 447, pl. 160, fig. 12.

Reference Yang, Ni, Li, Chen, Lin, Yu, Xia, Jiao, Fang, Ge and Mu1983

Climacograptus duplex basilaris Ge in Yang et al., p. 447, pl. 160, fig. 17.

Reference Ge1984

Climacograptus bellulus; Ge, p. 247, pl. 2, figs. 6–8.

Reference Ge1984

Climacograptus duplex; Ge, p. 250, pl. 3, figs. 7–11.

Reference Mu, Li, Ge, Lin and Ni2002

Climacograptus bellulus; Mu et al., p. 627, pl. 175, figs. 18–20 (with three references in synynomy).

Reference Mu, Li, Ge, Lin and Ni2002

Climacograptus bellulus wannanensis Li, Reference Li1984; Mu et al., p. 628, pl. 175, figs. 21, 22.

Reference Mu, Li, Ge, Lin and Ni2002

Climacograptus bicornis cf. crassispinus; Mu et al., p. 630, pl. 176, fig. 7.

Reference Mu, Li, Ge, Lin and Ni2002

Climacograptus bicornis crassipinus; Mu et al., p. 629, pl. 176, figs. 11, 15.

Reference Mu, Li, Ge, Lin and Ni2002

Climacograptus bicornis rigidus; Mu et al., p. 630, pl. 177, fig. 4.

Reference Mu, Li, Ge, Lin and Ni2002

Climacograptus duplex; Mu et al., p. 636, pl. 178, figs. 8, 9.

Figure 9.

Appendispinograptus longispinus (Hall, Reference Hall1902), line drawings: (1) NIGP 11759 (Sh2); (2) NIGP 11754 (Sh2); (3) NIGP 11809 (Sh9); (4) NIGP 11812 (Sh9); (5) NIGP 11811 (Sh5); (6) NIGP 11758 (Sh2); (7) NIGP 11756 (Sh2); (8) NIGP 11769 (Sh3); (9) NIGP 11807 (Sh10). Scale bars = 1 mm.

Type specimen

Lectotype, AMS F 46106, Stockyard Creek, Australia (Hall, Reference Hall1902, pl. 12, fig. 8), selected by Berry (Reference Berry1966, p. 437).

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West and East Qiqiaogou sections.

Description

Tubarium ~40 mm long, with a pair of long and pendent basal spines, making an arch with a length of nearly 20 mm. Proximal end of the tubarium ~1 mm wide, increasing gradually to a maximum width of 2 mm distally. One specimen reaching 2.6 mm in maximum width. Thecae of typical climacograptid type with parallel supragenicular walls and slightly inclined infragenicular walls. Geniculae sharp with horizontal apertural margins. 2TRD₂ = 1.00–1.55 mm; 2TRD₅ = 1.36–1.82 mm; 2TRD₁₀ = 1.45–2.27 mm; 2TRD_dist = 2.00–2.36 mm. Tubarium generally appearing to undergo torsion distally, with the facing direction of the thecal apertures rotated from ~45–90° over the length of the largest specimens.

Critical features of the species are the basal spines and the long and narrow parasiculae associated with them. Angle between two basal spines quite variable in the present material. Basal spines given off by each of the first two thecae at the points where they turn upward. Basal spines underlain by parasiculae of variable length and thickness. On the specimen illustrated in Fig. 9.2, parasicula first appearing at the mouth of the sicula. Following one budding off the first and crossing under the tubarium, around the virgella to the second stipe side. In a few specimens (Figs. 9.7, 11.8), parathecae growing out along the distal side of the basal spine for a short distance. Aperture of th1² covered by the paratheca, indicating the paratheca might originate from the theca. Paratheca continuing to lengthen over an extended interval during the growth of the mature tubarium. In most of the specimens, parasiculae and parathecae with similar lengths giving the impression of a single, broad pair of basal spines.

Remarks

The present specimens agree with most of the characters of the type specimen. Compared with the characters of the mature individuals described by Riva (Reference Riva1974b) and Koren’ et al. (Reference Koren’, Oradovskaya, Pylma, Sobolevskaya and Chugaeva1983), it differs in having a simple membrane system that includes only one pair each of paratheca and parasiculae, but a similar degree of tube development is present among specimens referred to the species by Štorch et al. (Reference Štorch, Mitchell, Finney and Melchin2011). Comparison to Appendispinograptus hanyuanensis is given above.

Figure 10.

Alulagraptus ensiformis (Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963), line drawings: (1) NIGP 11739 (Sh9); (2) NIGP 11744b (Sh9); (3) NIGP 11743 (Sh9, arrow indicates the crossbar lists connecting the nema and the lateral thecal walls); (4) holotype, NIGP 11749 (Sh9); (5) NIGP 11742a (Sh9); (6) NIGP 11737 (Sh9); (7) NIGP 11738 (Sh9); (8) NIGP 11746 (Sh9); (9) NIGP 11748 (Sh9); (10) NIGP 11735 (Sh9). Scale bars = 1 mm.

Figure 11.

Line drawings. (1) Appendispinograptus hanyuanensis (Ge in Mu et al., Reference Mu, Li, Ge, Chen, Lin and Ni1993), NIGP 11806 (Sh9). (2, 5, 6, 8) Appendispinograptus longispinus (Hall, Reference Hall1902): (2) NIGP 11751 (Sh11); (5) NIGP 11755 (Sh2); (6) NIGP 11810 (Sh6); (8) NIGP 11757 (Sh2). (3) Appendispinograptus cf. A. longispinus (Hall, Reference Hall1902), NIGP 11641 (Sh2). (4) Alulagraptus ensiformis (Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963), NIGP 11736 (Sh9). (7, 9) Diplacanthograptus spiniferus (Ruedemann, Reference Ruedemann1912): (7) NIGP 11734a (RHf139), Sijiagou Formation?, Jiutiaoling; (9) NIGP 11730 (RHf139), Sijiagou Formation?, Jiutiaoling. (10, 11, 13) Climacograptus bicornis (Hall, Reference Hall1847): (10) NIGP 11818 (RHf327), Tianzhu Formation?, Jiutiaoling; (11) NIGP 11820 (RHf333), Tianzhu Formation?, Jiutiaoling; (13) NIGP 11819 (RHf327), Tianzhu Formation?, Jiutiaoling. (12) Diplacanthograptus geniculatus (Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982), NIGP 11729b (SB1). Scale bars = 1 mm.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West Qiqiaogou section.

Remarks

The basal spines are more rapidly expanding than those of the type specimens of Appendispinograptus longispinus. Because we only have one incomplete proximal specimen at hand, we refer to it as Appendispinograptus cf. A. longispinus.

Type specimen

Lectotype, BU 1167, upper Hartfell shale, Dob's Linn, Scotland (Elles and Wood, Reference Elles and Wood1906, pl. 26, fig. 11c), selected by Riva (Reference Riva1974b, p. 120).

Figure 12.

Line drawings. (1–3, 6, 7) Pararetiograptus sp.: (1) NIGP 11907 (Sh2); (2) NIGP 11913 (Sh11); (3) NIGP 11906b (Sh11); (6) NIGP 11903 (Sh11); (7) NIGP 11907-1 (Sh2). (4, 11, 12) Diplacanthograptus geniculatus (Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982): (4) NIGP 11726 (SB1); (11) NIGP 11724 (SB1); (12) NIGP 11733a (RHf139), Sijiagou Formation?, Jiutiaoling. (5, 9, 10) Styracograptus tatianae (Keller, Reference Keller1956): (5) NIGP 11830 (Sh14); (9) NIGP 11875 (Sh5); (10) NIGP 11841 (Sh2). (8) Appendispinograptus supernus (Elles and Wood, Reference Elles and Wood1906), NIGP 11862 (Sh14). Scale bars = 1 mm.

Figure 13.

Light micrographs. (1–3) Dicellograptus sinicus Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963: (1) holotype, NIGP 11647 (Sh12); (2) NIGP 11649 (Sh12); (3) NIGP 11648 (Sh12). (4) Anticostia lata (Elles and Wood, Reference Elles and Wood1906), NIGP 11679 (Sh14). (5, 10) Orthograptus quadrimucronatus (Hall, Reference Hall1865): (5) NIGP 11662 (SB3); (10) NIGP 11665 (SB1). (6) Anticostia teres? (Perner, Reference Perner1895), NIGP 11696 (SB2). (7) Anticostia macgregorae Stewart and Mitchell, Reference Stewart and Mitchell1997, NIGP 11699 (SD4). (8) Styracograptus miserabilis? (Elles and Wood, Reference Elles and Wood1906), NIGP 11894 (RHf139), Sijiagou Formation?, Jiutiaoling. (9) Appendispinograptus supernus (Elles and Wood, Reference Elles and Wood1906), NIGP 11862 (Sh14). Scale bars = 1 mm.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Remarks

The present specimen bears basal spines that are slightly longer than those of the type material. It is similar to the juvenile forms of Climacograptus bicornis (Hall, Reference Hall1847) in general shape. In addition to differences in their proximal structure (not visible in the present material), this species differs from the latter in having a slightly narrower proximal end that widens to a lesser degree distally. Comparison to Appendispinograptus hanyuanensis is given above. See also detailed discussion by Loxton (Reference Loxton2017) for other comparisons.

Type species

Graptolithus bicornis Hall, Reference Hall1847.

Type specimen

Lectotype, AMNH 1030a, black shale in the lower part of the Austin Glen Greywacke, New York, USA (Hall, Reference Hall1865, pl. A, fig. 13), selected by Riva (Reference Riva1974a, p. 7).

Occurrence

Amplexograptus maxwelli beds, Tianzhu Formation? at Jiutiaoling.

Remarks

As a globally distributed species, the present form has been described by many authors from various countries. However, the present specimens bear prominent genicular flanges, which are possibly even extended into genicular spines on a few thecae. We did not separate them as an independent species because the character is only present on a few thecae and might not be a stable character.

Type specimen

Neotype, NIGP 11791 (Fig. 7.2), Xiehao Formation, Tianzhu, Gansu, China, designated here. Mu et al. (Reference Mu, Li, Ge, Chen and Zhang1963, pl. 23, fig. 8) illustrated a specimen with a detailed description, but without giving its collection number. This specimen is different from the ‘holotype’ designated later by Mu and Zhang (in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982, pl. 78, fig. 17). Thus, the specimen illustrated by Mu et al. (Reference Mu, Li, Ge, Chen and Zhang1963) should be the correct holotype of this species. However, that specimen cannot be found in the collections. Consequently, we designate the Mu et al. (Reference Mu, Song, Li, Xu and Zhang1982) specimen as the neotype herein.

Figure 14.

Light micrographs. (1) Anticostia thorsteinssoni (Melchin, Reference Melchin1987), NIGP 11703 (Sh13). (2) Anticostia macgregorae Stewart and Mitchell, Reference Stewart and Mitchell1997, NIGP 11704 (Sh13). (3) Anticostia lata (Elles and Wood, Reference Elles and Wood1906), NIGP 11659 (Sh5). (4, 7–9) Pseudoclimacograptus tianzhuensis Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982: (4) holotype, NIGP 11887 (Sh1); (7) NIGP 11884 (SC1); (8) NIGP 11896-1 (SC2); (9) NIGP 11896-2 (SC2). (5, 6, 10) Amplexograptus maxwelli (Decker, Reference Decker1935): (5) NIGP 11711 (Sh1); (6) NIGP 11716 (Sh1); (10) NIGP 11712b (Sh1). Scale bars = 1 mm.

Figure 15.

Light micrographs. (1, 5) Alulagraptus ensiformis (Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963): (1) NIGP 11738 (Sh9); (5) NIGP 11744b (Sh9). (2, 4) Styracograptus tatianae (Keller, Reference Keller1956): (2) NIGP 11830 (Sh14); (4) NIGP 11841 (Sh2). (3, 6–8) Climacograptus? papilio Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963; (3) NIGP 11795 (Sh10); (6) NIGP 11784b (Sh10-1); (7) NIGP 11781 (Sh13); (8) NIGP 11777 (Sh10-2). Scale bars = 1 mm.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the East Qiqiaogou section.

Description

Tubarium length to at least 30 mm, with a maximum width of 2.3 mm, which increases gradually from a proximal width of ~1 mm. Thecae with sharp geniculum, straight and parallel supragenicular walls as well as straight and oblique infragenicular walls. From one well-preserved specimen (Figs. 7.8, 15.7), short genicular flanges or spines extend from thickened genicular selvage. Median septum straight, beginning at approximately th8 (visible as a parallel-sided band surrounding the nema; Fig. 15.3, 15.8); nema commonly extending beyond to the end of the tubarium. Thecae generally remaining in similar profile along tubarium length, suggesting that the colony did not develop torsion during growth.

The most important feature is the fin-like or butterfly-like basal appendages that cover the proximal end of the tubarium above what appear to be prominent basal spines from the first thecal pair. In one specimen (Fig. 7.5), a portion of the basal spines is visible to extend beyond the incomplete appendages. Thus, we infer that the basal appendages continued to develop as the tubarium matured. In some specimens, a third fin-like structure occurs that might wrap around the virgella and the very proximal end of the tubarium (Fig. 7.1, 7.3). In different angles of preservations, the two fin-like appendages might overlap each over (Figs. 7.7, 15.7).

Remarks

Because the proximal end of the tubarium is usually shrouded by the appendages, the proximal structure is uncertain. For this reason, it is also possible that the present species might belong to Appendispinograptus and, therefore, we questionably retain the species in Climacograptus.

The present form superficially resembles Alulagraptus ensiformis in having basal web-like appendages, but in this case, they appear to be based on the basal thecal spines rather than scopular spines and, thus, are oriented at 90° to those of Alulagraptus ensiformis. This inference is supported by the fact that specimens are typically preserved in biprofile view (like other climacograptids with large basal spines on the first pair of thecae, e.g., the Appendispinograptus species discussed above), rather than in fully scalariform aspect as in Alulagraptus ensiformis. When the web-like structures break during the lateral compression, the broken appendages can be preserved in different layers of the black shale (Figs. 7.4, 15.3). Many of the web-like structures reveal a pattern of lines (Fig. 7) that recall those in the basal vanes or web-like structures of many climacograptids (Fig. 16.2). Uncompressed specimens of Climacograptus bicornis (see Bulman, Reference Bulman1945–1947), Appendispinograptus longispinus (see Mitchell et al., Reference Mitchell, Chen and Finney2007a), and Appendispinograptus supernus (see Loxton et al., Reference Loxton, Melchin, Mitchell and Senior2011) reveal that the membrane-like structures present in those species are in fact compressed parasicular and parathecal tubes that grew out of the aperture of the sicula and basal thecae. The present material is too poorly preserved to ascertain the original structure of basal appendages in C.? papilio, however, their general location and similarity to those of better known species suggest that these too could have comprised a stacked set of parasicular and parathecal tubes rather than a thin planar sheet.

Figure 16.

Appendispinograptus longispinus (Hall, Reference Hall1902), light micrographs: (1) NIGP 11812 (Sh9); (2) NIGP 11865 (Sh5); (3) NIGP 11764 (Sh3); (4) NIGP 11769 (Sh3); (5) NIGP 11822 (Sh13); (6) NIGP 11811 (Sh5); (7) NIGP 11768 (Sh3); (8) NIGP 11763 (Sh3); (9) NIGP 11766 (Sh3). Scale bars = 1 mm.

Figure 17.

Alulagraptus ensiformis (Mu and Zhang in Mu et al., Reference Mu, Li, Ge, Chen and Zhang1963), light micrographs: (1) NIGP 11745 (Sh9); (2) NIGP 11750 (Sh9); (3) holotype, NIGP 11749 (Sh9); (4) NIGP 11741 (Sh9); (5) NIGP 11743 (Sh9); (6) NIGP 11742a (Sh9); (7) NIGP 11747 (Sh9). Arrows indicate the crossbar lists connecting the nema and the lateral thecal walls. Scale bars = 1 mm.

Figure 18.

Alulagraptus uncinatus (Keble and Harris, Reference Keble and Harris1934), Phi Kappa Formation, Trail Creek Summit section, Idaho, USA (Mitchell et al., Reference Mitchell, Goldman, Cone, Maletz and Janousek2003), light micrographs: (1) USNM 725915, relatively mature specimen in typical scalariform view, second thecal series facing upward, sicular aperture visible in rounded proximal end and with slight web between septal spine and thecal wall on reverse side of colony; (2) USNM 725916, specimen showing branching of septal spines from termination of nema behind third thecal aperture and apex of sicula behind second (likely th2¹), note indistinct additional sicula on slab to lower left of proximal end of main specimen; (3, 5) USNM 725917: (3) juvenile colony with three thecae and forked nema projecting beyond growing end of colony, short sharp virgella and smooth sicular aperture; (5) interpreted image highlighting location of apertures of first thecal pair (green rings), sicula (s), which lacks normal prosicula but with nema (yellow strand) arising directly from apex of metasicula, and presence of crossbars on nema (xb); (4) USNM 725918, relatively mature specimen, obliquely compressed (subscalariform view), showing both thecal series and climacograptid-type thecae. Scale bars = 1 mm (1, 2, 4), or 0.5 mm (3).

Figure 19.

(1, 3, 7) Diplacanthograptus geniculatus (Mu and Zhang in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982): (1) NIGP 11724 (SB1); (3) NIGP 11733a (RHf139), Sijiagou Formation?, Jiutiaoling; (7) NIGP 11726 (SB1). (2, 4) Diplacanthograptus spiniferus (Ruedemann, Reference Ruedemann1912): (2) NIGP 11730 (RHf139), Sijiagou Formation?, Jiutiaoling; (4) NIGP 11734a (RHf139), Sijiagou Formation?, Jiutiaoling. (5, 9) Pararetiograptus sp.: (5) NIGP 11903 (Sh11); (9) NIGP 11906b (Sh11). (6, 8) Climacograptus bicornis (Hall, Reference Hall1847): (6) NIGP 11818 (RHf327), Tianzhu Formation?, Jiutiaoling; (8) NIGP 11819 (RHf327), Tianzhu Formation?, Jiutiaoling. Scale bars = 1 mm.

Figure 20.

Proximal part of the tubarium of Alulagraptus ensiformis, NIGP 11748, light micrograph. Arrows indicate the crossbar lists connecting the nema and the lateral thecal walls. Scale bar = 1 mm.

Type species

Climacograptus spiniferus Ruedemann, Reference Ruedemann1912.

Type specimen

Lectotype, NIGP 11734, the original specimen of Mu (Reference Mu, Li, Ge, Chen and Zhang1963, fig. 9b), designated here. Although they figured this specimen, Mu and Zhang (in Mu, Reference Mu1963b) did not describe the taxon and provided only a perfunctory comparison to Diplacanthograptus spiniferus. Thus, the name remained a nomen nudum until formally described by Mu and Zhang (in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982), who refigured this specimen along with NIGP 11725a. Neither they nor Mu et al. (Reference Mu, Li, Ge, Lin and Ni2002) specifically selected one of these two as the type specimen. Thus, we select the historically first illustrated specimen, NIGP 11734, as lectotype.

Occurrence

Diplacanthograptus geniculatus-Orthograptus quadrimucronatus beds, lower Sijiagou Formation at the Sijiagou section and Tianzhu Formation? at Jiutiaoling, China.

Description

Tubarium long and narrow with a length of as much as 22 mm and a very narrow width of 0.44–0.6 mm proximally, which increases gradually to 0.7–1.0 mm at th10, and a maximum width of 1.2–1.3 mm distally. Sicula and the growth of the proximal thecae are not clearly observed. However, virgella and mesial spine of the first thecae (th1¹) seem well developed and consist of a pair of asymmetrical basal spines. A short parasicula appears to be present on some specimens (e.g., Figs. 12.5, 19.7). Median septum is possibly complete, straight proximally and undulating distally.

Thecae with slightly concave supragenicular wall nearly parallel to tubarium axis, sharp geniculum, and straight, nearly horizontal aperture and infragenicular wall. Apertural margins and genicular flanges are thickened and generally extended into genicular spines. Ventral length of th1¹ = 0.57–0.6 mm; that of th1² = 0.6–0.75 mm. 2TRD₂ = 1.55–1.75 mm; 2TRD₅ = 1.9–2.2 mm; 2TRD₁₀ = 2.0–2.2 mm and distally.

Remarks

Mu (Reference Mu1963b) pointed out that the basal spines of the present form suggest affinities with Diplacanthograptus spiniferus. Tubaria of Diplacanthograptus geniculatus differ from those of other diplacanthograptids in being narrower with relatively long thecae that possess genicular spines.

Type specimen

Lectotype, AMNH 1041/5a, possibly from the basal Utica shale, Ballston Spa, New York, USA (Riva, Reference Riva1974b, pl. 1, figs. 4, 8).

Occurrence

Diplacanthograptus geniculatus-Orthograptus quadrimucronatus beds, Tianzhu Formation? at Jiutiaoling, China.

Remarks

Diplacanthograptus spiniferus is a globally distributed species and the specimens at hand agree with the characters of the type material. The species was thoroughly redescribed by Riva (Reference Riva1974a) and its relationship to Diplacanthograptus geniculatus is discussed above.

Type species

Climacograptus tubuliferus Lapworth, Reference Lapworth1876.

Type specimen

Lectotype, BU 1150, upper Hartfell shales, Dob's Linn, Scotland (Elles and Wood, Reference Elles and Wood1906, text-fig. 120a), selected by Williams (Reference Williams1987, p. 79).

Occurrence

Diplacanthograptus geniculatus-Orthograptus quadrimucronatus beds, Tianzhu Formation? at Jiutiaoling, China.

Remarks

The single, immature specimen does not justify full description but exhibits the characteristically long proximal thecae (the upward-grown portions of both th1¹ and th1² are ~1 mm long), which increase slowly in length distally. The present material corresponds well to the characters of the type material (restudied by Goldman et al., Reference Goldman, Mitchell, Melchin, Fan, Wu and Sheets2011). The comparatively long thecae give the colony an elongate, narrow appearance. In contrast, the similar Styracograptus tatianae (Keller, Reference Keller1956) is equally narrow but generally widens more rapidly and has much more closely spaced thecae in the proximal end.

Holotype

Specimen (37) from the Dulankarinsky Horizon, Chi-Illi Mountains, Kazakhstan (Keller, Reference Keller1956, fig. 25). Deposited in the Geological Institute of the USSR Academy of Sciences.

Occurrence

Appendispinograptus longispinus Biozone, Xiehao Formation at the West and East Qiqiaogou sections.

Remarks

The characters of the present specimens resemble that of the type material in size and form. The upward-grown portions of the first thecal pair are 0.36–0.41 mm in the present material. Thecal length increasing substantially distally; 2TRD₅ = 1.1–1.3 mm; 2TRD₁₀ = 1.7 mm. Note the slightly thickened nema (Fig. 15.2) and gently recurved virgella (Figs. 13.8, 15.2), which are common in this species. Although the long and oblique virgella is not well preserved in two of the specimens (Fig. 12.9, 12.10) and proximal structure is not preserved, the narrowly rounded proximal end of the tubarium in all of the present specimens is typical.

Type species

Climacograptus scharenbergi Lapworth, Reference Lapworth1876.

Holotype

NIGP 11887 (Figs. 8.2, 14.4), preserved in relief, originally illustrated and designated by Mu and Zhang (in Mu et al., Reference Mu, Song, Li, Xu and Zhang1982, pl. 77, fig. 24).

Occurrence

Amplexograptus maxwelli beds, Tianzhu Formation at the West Qiqiaogou and Sijiagou sections, China.

Description

Tubarium long and narrow with a length of 23 mm. Width increasing slightly from 0.55–0.65 mm at the proximal end to a uniform distal width of 0.7–1.0 mm (1.5 mm distally in one specimen). A possible long and narrow sicula is poorly preserved. Occurrence of a diamond-shaped patch in the central region at the proximal end suggests a Pattern C proximal development (Fig. 6.6; Mitchell, Reference Mitchell1987). Proximal end is narrowly rounded and both of the first pair of thecae exhibit substantial upward growth. A mesial spine is present on th1¹. Undulating or zigzag median septum is well developed in most individuals, probably arising from th2² or delayed to th3² or th4¹. Short horizontal prothecal septa and intrathecal folds are present in the proximal part of the tubarium in the holotype and other specimens. Thecae elongated, of climacograptid type with sharp geniculae; supragenicular walls parallel to colony axis and ranging from slightly convex to slightly concave; infragenicular walls double sigmoid. Apertures are relatively large, with simple horizontal to slightly introverted apertural margins, occupying one quarter to one third of the width of the tubarium. 2TRD₂ = 1.1–1.15 mm; 2TRD₅ = 1.2–1.5 mm; 2TRD₁₀ = 1.2–1.75 mm; 2TRD_dist = 1.6–2.2 mm in a few specimens.

Remarks

The present materials include specimens with variable tubarium width and thecal spacing. Some of these specimens might belong to Styracograptus, however, we provisionally include all them within one species in light of the limited number of specimens and their endemic occurrence.