Cyrtospirifer Nalivkin, 1924
publication ID |
https://doi.org/ 10.5281/zenodo.13742176 |
persistent identifier |
https://treatment.plazi.org/id/4836037D-D663-6C48-FFBF-D7D6FBB2F93A |
treatment provided by |
Felipe |
scientific name |
Cyrtospirifer Nalivkin, 1924 |
status |
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Genus Cyrtospirifer Nalivkin, 1924 View in CoL in Frederiks 1924 Cyrtospirifer cf. extensa Ching and Liu, 1982 in Wang et al. 1982
Fig. 11G View Fig .
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 View Fig ), correlated with the Palmatolepis hassi conodont Zone.
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