Cyrtospirifer Nalivkin, 1924

Ma, Xue-Ping, Becker, Ralph Thomas, Li, Hua & Sun, Yuan-Yuan, 2006, Early and Middle Frasnian brachiopod faunas and turnover on the South China shelf, Acta Palaeontologica Polonica 51 (4), pp. 789-812 : 804

Genus Cyrtospirifer Nalivkin, 1924 in Frederiks 1924 Cyrtospirifer cf. extensa Ching and Liu, 1982 in Wang et al. 1982

Fig. 11G .

1982 cf. Cyrtospirifer extensa Ching et Liu (sp. nov.); Wang et al. 1982: 237–238, pl. 74: 8a–e.

Material.—One more or less complete shell (figured) and two poorly preserved dorsal valves from the Lungkouchung Formation in the Qiziqiao section (sample QZQ1).

Discussion.—The studied specimens have the following main features: delthyrial plate covering posterior 1/3 of delthyrium, sinal plications generally fewer than 10 in number, with 1 lateral sinal plication on each side and a pair of simple primary plications, flank plications about 23 on each side, rounded and separated by deep furrows of about same width, shell material thin with secondary fibrous layer developed and secondary thickening is not developed (so that plication pattern can be imprinted on internal mould surface).

The shell outline is similar to that of Cyrtospirifer extensa Ching and Liu in Wang et al. (1982) from the Frasnian of eastern South China (Lianhua County, Jiangxi Province), but differs in having a large ventral interarea (versus a short and low interarea in C. extensa although its shell size is even larger). It is distinct from Cyrtospirifer ? variabilis Ma and Sun, 2001 from the Shetianqiao and Xikuangshan sections in having a much more transverse shell outline and a well developed delthyrial plate (versus a very short delthyrial plate in Cyrtospirifer ? variabilis).

Occurrence.—The present species occurs in Bed 14 of the Qiziqiao section ( Fig. 2 ), correlated with the Palmatolepis hassi conodont Zone.

Figures

Fig. 11. Plicate spiriferid brachiopods from the Frasnian of the Qiziqiao and Qifengzhen sections. A. Theodossia? sp. PUM05027, sample QZQ4, Qiziqiao section, probably early Late Frasnian (cardinal extremities somewhat broken), ventral (A1), area (A2), and lateral (A3) views of a ventral valve. B–D. Cyrtospirifer? sp. B. PUM05028, sample QZQ3, Qiziqiao section, Middle Frasnian, dorsal (B1), posterior (B2), ventral (B3), lateral (B4), and anterior (B5) views of a juvenile.C. PUM05029, sample QZQ1, Qiziqiao section, Middle Frasnian, posterior (C1), lateral (C2), anterior (C3), dorsal (C4), and ventral (C5) views, note the thick shell material. D. PUM05030, sample QZQ1–3, Qiziqiao section, Middle Frasnian, ventral interior (D1), lateral (D2), and ventral exterior (D3) views, note thickened ventral posterior. E, F. Cyrtospirifer cf. sichuanensis Chen in Xu et al. (1978). E. PUM05031, dorsal view of a heavily exfoliated specimen of sample GQ6 of the Qifengzhen section in the vicinity of Guilin, about 17 m above the base of the “Gubi Formation” (Zhong et al. 1992). F. PUM05032, sample QZQ1, Qiziqiao section, Middle Frasnian, ventral view of an entirely exfoliated specimen. G. Cyrtospirifer cf. extensa Ching et Liu in Wang et al. 1982; PUM05033, sample QZQ1, Qiziqiao section, Middle Frasnian (cardinal extremities somewhat broken), anterior (G1), dorsal (G2), ventral (G3), lateral (G4), and posterior (G5) views. H. Pyramidaspirifer cf. helenae (Fenton, 1918); PUM05034, sample QZQ4, Qiziqiao section, probably early Late Frasnian, dorsal (H1), ventral (H2), lateral (H3), area (H4), and anterior (H5) views of a slightly distorted shell.

Fig. 2. Stratigraphy and distribution of Early and Middle Frasnian brachiopods in South China. Most but not all known brachiopods are described and illustrated in this paper. For the distribution of atrypids in the Dushan section, for example, see Ma et al. (2005). The stratigraphy of Panxi and the occurrence of Cyrtospirifer sp. are based on Yunnan compiling group (1978) and the occurrence of Stringocephalus in the lower part of the Yidade Formation is as in Xian et al. (1988: 148). The stratigraphy of Dushan and the occurrence of Stringocephalus sp. are as in Liao et al. (1979); the Caiziyan section was re−measured by Long−Ming Wei, Xue−Ping Ma, and Hua Li (personal communication 2005), with coral identifications by Wei−Hua Liao. The stratigraphy of Qiziqiao is based on data of Z.−X. Hu and Z.−Q. Deng in Tan et al. (1987), and the occurrence of Yunnanella sp. is based on Zu−Han Liu (personal communication 2001). Abbreviations: calc., calcareous; argill., argillaceous; C., Cyrtospirifer; Pa., Palmatolepis; Po., Polygnathus; S., Spinatrypina.