944


Journal of Paleontology 91(5):933–959


Reillustrated specimens include the holotype exoskeleton of Arthricocephalus (Arthricocephalites) pulchellus Zhang and Qian in Zhang et al., 1980 (NIGP 38233) and two exoskeletons assigned by Lei (2016) to Arthricocephalus chauveaui Bergeron (NIGP 163346, 163357).


Remarks.—A new diagnosis and description of Arthricocephalus chauveaui are presented here because the concept of the species and the genus are significantly revised. Most species that were previously referred to A.(Arthricocephalites), Arthricocephalites, and Haliplanktos are now synonymized with A. chauveaui either because they closely resemble the lectotype exoskeleton of A. chauveaui (E.M. 90001a), or because they closely resemble meraspides of the species. Material from the Balang Formation of northwestern


Hunan and eastern Guizhou shows that the holaspid exoskeleton of Arthricocephalus chauveaui has eight thoracic segments. This suggests that some species referred to Arthricocephalus, A. (Arthricocephalites), and Haliplanktos and the assigned species with fewer than eight thoracic segments are all based on meraspides. Those species are: Arthricocephalus taijiangensis, A. pulchellus, A.(Arthricocephalites) jishouensis (also pub- lished as Haliplanktos jishouensis), and A.(Arthricocephalites) tongrenensis. Arthricocephalus taijiangensis (Yin and Li, 1978, pl. 156, fig. 8) is based on an individual having five thoracic segments. Arthricocephalus (Arthricocephalites) tongrenensis (Yin and Li, 1978, pl. 157, fig. 17) is based on an individual having seven thoracic segments. Holotypes of A.(Arthricocephalites) jishouensis (Zhou et al., 1977, pl. 42, fig. 4) and A.(Arthricocephalites) pulchellus (Zhang et al., 1980, pl. 92, fig. 3) are individuals having six thoracic segments. Blaker and Peel (1997, p. 109) referred the type material of


Ovatoryctocara granulata (Chernysheva 1962, pl. 5, figs. 6–8) to Arthricocephalus chauveaui. As discussed above, their concept of A. chauveaui embraced both A. chauveaui and Oryctocarella duyunensis. Based on a rather large number of specimens now known from Russia, Greenland, and Newfound- land (e.g., Fletcher, 2003; Korovnikov and Shabanov, 2008; Naimark et al., 2011; Geyer and Peel, 2011), it is evident that Ovatoryctocara granulata is distinct from both A. chauveaui


that is commonly defined by sinuous axial furrows, a pair of longitudinal furrows connecting S1–S3, pit-like glabellar furrows exsagittally, and a palpebral lobe that is moderately close to the glabella. The thorax of O. granulata has only four segments in the holaspid stage, and the pygidium is


and O. duyunensis. It differs in having a prominent preocular field that is relatively long (as compared to the short preocular field in A. chauveaui and O. duyunensis), in having a glabella


proportionally longer than that of either A. chauveaui or O. duyunensis; it has more axial rings and lacks a border. In their synonymy of A. chauveaui, Blaker and Peel (1997,


p. 110) referred some additional Russian specimens to A. chauveaui. They include a pygidium assigned to Neopagetina nomokonovi by Semashko (1969, pl. 1, fig.13) and a cranidium and a pygidium referred to Oryctocara (Ovatoryctocara) sp. by Chernysheva (1971, pl. 13, figs. 8, 9). However, the illustrations of these specimens show that they do not belong to either Arthricocephalus, as revised here, or to Oryctocarella. They are more likely specimens of the genus Ovatoryctocara. As revised, some whole or partial specimens that were


previously assigned to A. chauveaui are now referred to Oryctocarella duyunensis Qian, 1961 (e.g., Qian, 1961; Lu and Qian, 1964; Zhou et al., 1977; Zhang et al., 1980; Lane et al., 1988; Blaker and Peel, 1997; Yuan et al., 2002, 2006; McNamara et al., 2003; Geyer, 2005; Peng et al., 2005a, 2005b; 2006).


Arthricocephalus xinzhaiheensis Qian and Lin in Lu et al., 1974 Figure 5


1974 1974 1978 1978 1980


1980


?1980 2002


2006 2016 2016


Arthricocephalus (Arthricocephalites) xinzhaiheensis Qian and Lin in Lu et al., p. 95, pl. 36, fig. 7.


Arthricocephalus (Arthricocephalites) intermedius Zhou in Lu et al., p. 95, pl. 36, fig. 8.


Arthricocephalus (Arthricocephalites) intermedius; Yin and Li, p. 441, pl. 156, fig. 10.


Arthricocephalus (Arthricocephalites) xinzhaiheensis; Yin and Li, p.441,pl. 157, fig. 1.


Arthricocephalus (Arthricocephalites) xinzhaiheensis;


Zhang et al. (part), p. 276, pl. 92, figs. 5, 6; non pl. 93, fig. 1.


Arthricocephalus (Arthricocephalites) intermedius; Zhang et al., p. 278, pl. 92, fig. 4.


Arthricocephalites (Arthricocephalites) sp. 2, Zhang et al., p. 279, pl. 93, fig. 8.


Arthricocephalites xinzhaiheensis; Yuan et al., p. 123, pl. 30, figs. 6, 7.


non 2003 Arthricocephalus xinzhaiheensis; McNamara et al., p. 111, pl. 2, figs. 1–4, text-fig. 4A–D.


Arthricocephalites xinzhaiheensis; Yuan et al. (part), p. 617, fig 2a; non fig. 2b.


Arthricocephalites xinzhaiheensis; Shen et al., (part), fig. 1.1–1.7; non fig. 1.8–1.11.


Arthricocephalus chauveaui Bergeron; Lei (part), p. 496, figs. 3.5, 3.7, 3.13, 4.2, 4.7; non figs. 3.1–3.4, 3.6, ?3.8, 3.9–3.12, 3.14, ?3.15, 4.1–4.3, 4.5, 4.6, 4.8, ?4.9–4.16.


Figure 5. Arthricocephalus xinzhaiheensis Qian and Lin in Lu et al., 1974 from the Balang Formation in eastern (1, 2, 6–8) and southeastern (3) Guizhou and northeastern Hunan (4, 5, 9–13), China; all in dorsal view. White arrowhead indicates the posterior margin of thorax; arrowhead with black outline indicates the posterior margin of partially released segment of transitory pygidium; b = border, d = doublure, f = facet: (1) holotype, NIGP 38234, exoskeleton, KH071, original of Lu et al. (1974, pl. 36, fig. 7); (2) NIGP 38235, exoskeleton, KH070, original of Arthricocephalus (Arthricocephalites) xinzhaiheensis Qian and Lin (Zhang et al., 1980, pl. 92, fig. 6); (3) NIGP 21481, exoskeleton, DZ-53-upper, original of Arthricocephalus (Arthricocephalites) intermedius Zhou (Lu et al., 1974, pl. 36, fig. 8); (4) NIGP 163350, exoskeleton, XHZA 416-14, original of Lei (2016, fig. 3.7); (5) NIGP 164843, exoskeleton, meraspis degree 6, LYX-1; (6) NIGP 135415, exoskeleton, meraspis degree 5, GY(GPN2), original of Arthricocephalus balangensis (McNamara et al., 2003, pl. 2, fig. 6); (7) NIGP 135416, exoskeleton, meraspis degree 6, GY(GPN2), original of Arthricocephalus balangensis (McNamara et al., 2003, pl. 2, fig. 8); (8) NIGP 135417, exoskeleton, meraspis degree 7, GY(GPN2), original of Arthricocephalus balangensis (McNamara et al., 2003, pl. 2, fig. 9); (9) NIGP 163356, incomplete exoskeleton, meraspis degree 7, XHZA 351-15, original of Lei (2016, fig. 4.13); (10–11) NIGP 163348, holaspid exoskeleton (10), and latex cast from its external mold (11), XHZA404-13, original of Lei (2016, fig. 3.5); (12) NIGP 163365, cephalon with displaced right librigena and lacking left librigena, XHZA416-5, original of Lei (2016, fig. 4.7); (13) NIGP 163362, cranidium, XHZA404-20, original of Lei (2016, fig. 4.4). All scale bars represent 1.0mm.


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