934


Journal of Paleontology 91(5):933–959


Figure 1. Slab with the type series of Arthricocephalus chauveaui Bergeron, 1899, reassigned to three species, each in a separate genus; from the Balang Formation, north of Tongren, eastern Guizhou, China. Museum of the Geological Department, Claude Bernard University, Lyon, France, E.M. 90001. Sclerites (1–6, 8) were renumbered as E.M. 90001a–g by Lane et al. (1988). An external mold of incomplete cephalon (7) was not previously illustrated and now numbered E.M. 90001h. (1–2) Arthricocephalus chauveaui Bergeron, 1899: (1) disarticulated holaspid exoskeleton; (2) external mold of holaspid pygidium. (3–7) Oryctocarella duyunensis (Qian, 1961): (3, 4) two meraspid exoskeletons; (5) external mold of cranidium; (6) thoracopygon; (7) external mold of incomplete cephalon. (8) Duyunaspis duyunensis Zhang and Qian in Zhou et al., 1977, meraspid exoskeleton. See also caption of Figure 2 for detailed description of each specimen. Scale bar = 10mm.


based on 10 sclerites preserved on the bedding surface of a small slab of limestone (Fig. 1). The slab is composed of lime mud- stone, and measures 6.2cm by 3.8 cm. It was collected from the Balang Formation, north of Tongren, eastern Guizhou, South China, and sent to France by M. Chauveau for study by Bergeron. The sclerites on the slab include five exoskeletons in varying degress of articulation, a small external mold of an incomplete meraspid cephalon, and an external mold of a holaspid pygidium (Figs. 1, 2.1–2.12). Bergeron (1899)


evidently considered the specimens to be conspecific, and used all of them to establish the morphologic limits of A. chauveaui. The original publication included one illustrated specimen, a dorsal exoskeleton lacking the free cheeks (reproduced here as Fig. 2.1). Bergeron’s (1899) original concept of A. chauveaui was


generally accepted by subsequent authors including Lane et al. (1988), Blaker and Peel (1997), and McNamara et al. (2003). Lane et al. (1988) regarded all of the sclerites present on


Figure 2. Original illustration (1) and type series (2–12)of Arthricocephalus chauveaui Bergeron, 1899, from the Balang Formation, north of Tongren, eastern Guizhou, China; all sclerites are on a single slab, all in dorsal view unless stated otherwise. White arrowhead indicates posterior margin of thorax; arrowhead with black outline indicates the posterior margin of partially released segment of transitory pygidium; black triangles indicate posteromedial notch on pygidial border; b = border, c = connective suture, d = doublure. (1–3, 10, 11) Arthricocephalus chauveaui Bergeron, 1899: (1) line-drawing of exoskeleton, illustrated as fig. 9 in Bergeron (1899); (2) E.M. 90001a, type specimen, designated as lectotype, disarticulated holaspid exoskeleton with inverted cranidium, librigena and rostral-hypostomal plate; (3) reversal of image in 2 (lectotype), from negative film; (10) latex cast from external mold of rostral-hypostomal plate and cephalic doublure of specimen in 2 and 3 (lectotype), ventral view; (11) E.M. 90001g, latex cast of external mold of pygidium; dark curved region at margin is the mold of the pygidial doublure; part of the upturned border is preserved at left upper corner of pygidium. (4–9) Oryctocarella duyunensis (Qian, 1961), specimens determined by Lane et al. (1988) as A. chauveaui:(4) E.M. 90001c, disarticulated thoracopygon, posterior margin of thorax uncertain (arrows indicate alternative possibilities); specimen may be meraspid degree 10 or early holaspid (11 segments); (5) E.M. 90001b, inverted cranidium, external mold in ventral view, illustrated and designated as the lectotype of Arthricocephalus chauveaui by Lane et al. (1988, pl.1, fig. 2); (6) latex cast from external mold of cranidium in 5; (7, 8) two meraspid exoskeletons lacking librigenae: (7) E.M. 90001d, meraspid degree 9; (8) E.M. 90001e, meraspid degree 8; (9) E.M. 90001h, latex cast of external mold of incomplete meraspid cephalon in Figure 1.7. (12) Duyunaspis duyunensis Zhang and Qian in Zhou et al., 1977: E.M. 90001f, meraspid exoskeleton, specimen identified as meraspid degree 5 or 6 of A. chauveaui by Lane et al. (1988). All scale bars represent 1.0mm.


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