Theodossia, Nalivkin, 1925
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publication ID |
https://doi.org/ 10.5281/zenodo.13742176 |
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persistent identifier |
https://treatment.plazi.org/id/4836037D-D663-6C48-FFBF-D3EFFD53FA77 |
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treatment provided by |
Felipe |
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scientific name |
Theodossia |
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Theodossia View in CoL ? sp.
Fig. 11A View Fig .
Material.— Sample QZQ4 (five specimens including dorsal and ventral valves). Qiziqiao section, probably Late Frasnian .
Discussion.—The species has about 22–25 costae on each flank and is tentatively assigned to Theodossia by its sinus (without bounding plications), and lack of delthyrial plate. The type species of Theodossia ( T. anossofi ) as figured by Verneuil (1845: 153–155, pl. 4: 3) possesses much coarser costae and a much shorter hinge. Sample DS65 (Dushan section, Middle Frasnian) is similar to the type species (the plicate spiriferids of the Dushan section will be described in a separate paper). Shell ornamentation of the studied species is similar to that of T. hungerfordi (Hall, 1858) from the Late Frasnian of Iowa ( USA), especially sinal ornamentation (i.e., with the exception of the central costa that bifurcates anteriorly and is finer, other sinal costae simple and almost as strong as flank plications); beyond this, differences between the two forms are obvious in many respects: ventral area (catacline to slightly curved apsacline versus curved apsacline), sinus (with totally 13 sinal costae at anterior commissure, triangular in cross section versus shallow, flat−bottomed), and shell shape (transverse versus sub−rounded).
Occurrence.—Qiziqiao section ( Fig. 1 View Fig ), correlated with the lower part of the Early Palmatolepis rhenana conodont Zone.
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