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 : 806

Cyrtospirifer ? sp.

Figs. 11B–D , 12B , 14 .

Material.— Fifteen ventral valves, mostly poorly preserved, including 14 from sample QZQ1 and one from sample QZQ1–3 ; two complete shells, including one from sample QZQ1 and one juvenile from sample QZQ3 . One ventral valve from Middle Frasnian Dushan section (sample DS64) is questionably assigned here .

Discussion.—Main features of this species are: shell material thick and dorsal adductor muscle field narrow, with anterior pair elongated and deeply incised, separated by a low myophragm. This species differs from other species of Cyrtospirifer in its greatly thickened ventral posterior, instead of a delthyrial plate. It is similar to North American Regelia (Middle to Late Frasnian), but differs in having a more curved ventral interarea (versus a much less curved to a catacline ventral interarea in Regelia ).

Occurrence.—So far this species is mainly present in Bed 14 of the Qiziqiao section of central Hunan, 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. 12. A. Sinal plication pattern of Cyrtospirifer cf. sichuanensis Chen, 1978, specimen illustrated on Fig. 11F. B. Sinal plication pattern of Cyrtospirifer? sp., specimen illustrated on Fig. 11C.

Fig. 14. Transverse serial sections of Cyrtospirifer? sp., sample QZQ1, Qiziqiao section, Middle Frasnian. Specimen PUM05037, acetate peel number 05D. Numbers refer to approximate distance in mm from the ventral apex; numbers 1–6 on the lateral profile indicate the successive position of sections.