Cymoceras sp.

Dernov, Vitaly, 2022, Late Bashkirian Ammonoids From The Mospyne Formation Of The Donets Basin, Ukraine, Fossil Imprint 78 (2), pp. 489-512 : 497-498

Cymoceras sp.

Text-fig. 7b, c

M a t e r i a l. One poorly preserved specimen from stratigraphic level 5b of the Mospyne Formation.

D e s c r i p t i o n. Specimen IGSU-4/573 is a fully limonitized specimen of 42.0 mm diameter ( Text-fig. 7b ). The conch is extremely discoidal (ww/dm = 0.29) with narrow and strongly convex venter; it merges imperceptibly into the broad flattened flanks. Ornamented with fine biconvex ribs that form a narrow sinus and projection on the ventrolateral area. On the ventrolateral area the ribs are spaced about 0.2 to 0.3 mm apart. The suture line has a narrow, sharply pointed lateral prong from the external lobe and high, narrow ventrolateral saddle; this saddle merges in the middle of the flank into a narrow, V-shaped pointed adventive lobe ( Text-fig. 7c ). The suture line is not preserved in the middle part of the venter and lower part of the flank.

R e m a r k s. Cymoceras sp. differs from Cymoceras miseri MCCALEB, 1964 in a wider ventrolateral saddle.

O c c u r r e n c e. Late Bashkirian, Mospyne Formation; Donets Basin ( Ukraine).

Figures

Text-fig. 7. Ammonoids from the Mospyne Formation. a: Anthracoceratites sp., lateral view; specimen IGSU-4/3634. b, c: Cymoceras sp., lateral view (b), fragment of the suture line in a 42 mm diameter conch (c); specimen IGSU-4/573. d, e: Neodimorphoceratidae indet., lateral view (d), surface ornamentation on the flank (e); specimen IGSU-4/5350. Scale bars 10 mm.