Peng et al.—Revision of oryctocephalid genra
1982 Duyunaspis duyunensis; Liu, p. 299, pl. 213, fig. 10. 1988 Arthricocephalus chauveaui; Lane et al. (part), p. 555, pl. 1, fig. 4; non pl. 1, figs. 1–3, 5, 6.
957
2001a Duyunaspis sp., Zhao et al., p. 180, pl. 1, fig. 3. 2001 Duyunaspis duyunensis; Yuan et al., p. 224, pl. 1, fig. 6.
2006 Duyunaspis duyunensis; McNamara et al., p. 7, pl. 2, figs. 5–18, text-fig. 5.
2014 Duyunaspis duyunensis; Lei and Peng, 2014, p. 354, figs. 3, 5b.
Holotype.—Incomplete exoskeleton (Zhou et al., 1977, p. 132, pl. 41, fig. 5), NIGP 38228, from the Balang Formation, Palang, Duyun, southeastern Guizhou, China; by original designation.
Diagnosis.—As for the genus.
Occurrence.—From dark-gray calcareous mudstone and shale (weathering yellow-green) in the middle part of the Balang Formation, eastern and southeastern Guizhou, western and northwestern Hunan, South China (Jiangnan Slope Belt); Cambrian Stage 4, Duyunian Stage of the regional stratigraphic scheme.
Description.—The description in McNamara et al. (2006, p. 11–12), which applies to specimens from the protaspid period through meraspid degree 7, is slightly emended here. Apart from additional thoracic segments, the specimens of meraspis degree 8 (with eight thoracic segments) and holaspides (with nine thoracic segments) both resemble the meraspid degree 7 exoskeleton. Hypostome shield-shape; middle body inflated, divided
into a long anterior lobe, and a crescentic posterior lobe by a faint medial furrow; macula deeply incised, located near mid- length of the middle body; lateral and posterior border narrow, strongly upturned; anterior wing triangular, with subequal length and width, anterior margin (hypostomal suture?) gently arched forward. Pygidial border gently upturned, defined by a shallow
and broad border furrow. Posterior margin with distinct, broad notch.
Materials.—10 exoskeletons (NIGP 164871–164880).
Remarks.—Based on a large collection of 766 exoskeletons from the Balang Formation at Paiwu, Huayuan, northwestern Hunan, Lei and Peng (2014, p. 355–356) synonymized five earlier described species of Duyunaspis withD. duyunensis. The characters previously used to distinguish the species were regarded by Lei and Peng (2014) as the result of either intras- pecific variation or taphonomic alteration. The synonymized species are Duyunaspis guzhangensis Zhou (in Zhou et al., 1977, p. 132, pl. 41, fig. 7); Duyunaspis songtaoensis Qian and Lin (in Zhou et al., 1977, p. 132, pl. 41, fig. 8); Duyunaspis
briaris Qian and Lin (in Yin and Li, 1978, p. 445, pl. 156, fig. 4); Duyunaspis obesis Qian and Lin (in Zhang et al., 1980, p. 274, pl. 90, fig. 6); and Duyunaspis laevigatus Qian and Lin (in Zhang et al., 1980, p. 274, pl. 91, figs. 7–9). Duyunaspis briaris and D. obesis are objective synonyms because both are based on the same holotype cranidium. The types of all five
2015 Duyunaspis duyunensis; Peng et al., p. 89, pl. 1, fig. 10.
synonymized species are preserved in greenish-yellow shale or mudstone. Some variation among them is probably the result of intraspecific variation (Lei and Peng, 2014, p. 359, table 1). However, the fossils are mostly flattened and distorted, leading to variation in proportions of the exoskeleton and variation in the expression of axial and glabellar furrows. The glabellar furrows have been either enhanced or nearly obliterated through taphonomic distortion. Glabellar furrow S1, which consists of isolated pits separated from the axial furrows in well-preserved cranidia, may attain a transglabellar extent after taphonomic compaction. The thorax of Duyunaspis duyunensis has been reported to
consist of either eight segments (Zhang and Qian in Zhou et al., 1977, p. 182) or seven segments (McNamara et al., 2006, p. 10) in the holaspid period. Lei and Peng (2014, p. 355), however, showed that the holaspid exoskeleton has as many as nine thoracic segments (Lei and Peng, 2014, fig. 3.10–3.16; Fig. 10.11, 10.12). Duyunaspis paiwuensis (Lei and Peng, 2014, fig. 4), from
the lower part of the Balang Formation at Paiwu, northwestern Hunan, resembles D. duyunensis in the overall exoskeleton morphology. Duyunaspis paiwuensis differs from the latter species mainly in having a proportionally broader and shorter cephalon, a narrower and longer glabella, a narrower thoracic axis (narrower than the pleural region), and a fulcrum that is located further abaxially from the axial furrow.
Acknowledgements
We thank J. Vannier (Lyon) for providing access to facilities during SP’s visit, and Bertrand Lefebvre (Lyon) for preparing the latex cast of the Bergeron’s slab. We thank P.D. Lane (Keele) for recalling information about the preparation of his co- authored 1988 paper; Y. Li (Nanjing) for offering collection LYX-1; I.V. Korovnikov (Novosibirsk) for providing images of topotypic specimens of Oryctocarella sibirica; S. Clausen (Lille) for improving the English translation of Bergeron’s (1899) paper; and T.V. Pegel (Novosibirsk) for access to Russian literature. We are also greatly indebted to J. Jago (Adlaide) and G. Geyer (Würzburg) for their helpful comments and suggestions for improving the manuscript, and to B. Hunda (Cincinnati), and N. Hughes (Riverside) for their accurate editorial work. Funding was provided by the National Natural Science Foundation of China to SP (41330101, 41521061, 41290260) and to XZ (41672002), by the Ministry of Science and Technology of China (2015FY31010), and by Regional Geological Survey of Guizhou Province (12120114068201); a grant was provided by the Subsurface Energy Research Cen- ter, The Ohio State University to LEB.
References
Beecher, C.E., 1897, Outline of a natural classification of the trilobites: American Journal of Sciences, Series 3, v. 46, p. 142–147.
Bergeron, J.N., 1899, Étude de quelques trilobites de Chine: Bulletin de la Société Géologique du France, Series 3, v. 27, p. 499–516.
Blaker, M.R., 1986, Notes on the trilobite fauna of the Henson Gletscher For- mation (Lower Cambrian) of the central North Greenland: Grønlands Geologiske Undersøgelse, Report 132, p. 65–73.
Blaker, M.R., and Peel, J.S., 1997, Lower Cambrian trilobites from North Greenland: Meddelelser om Grønland, Geoscience, v. 35, 145 p.
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