Gastrioceras kutejnikovense POPOV , 1979

Dernov, Vitaly, 2022, Late Bashkirian Ammonoids From The Mospyne Formation Of The Donets Basin, Ukraine, Fossil Imprint 78 (2), pp. 489-512 : 503

Gastrioceras kutejnikovense POPOV, 1979

Text-fig. 9j, k

1979 Gastrioceras kutejnikovense ; Popov, p. 84, pl. XI, fig. 3.

H o l o t y p e. Specimen VSEGEI- 69 in the Russian Geological Research Institute (St. Petersburg, Russia); figured by Popov (1979: pl. XI, fig. 3).

Ty p e l o c a l i t y a n d s t r a t i g r a p h i c h o r i z o n. Zapovidka Ravine near Kuteynikove, Donetsk Region, Ukraine; the G 3 or G 4 limestone layer of the Mospyne Formation.

D i a g n o s i s. Gastrioceras with pachyconic conch with weakly compressed whorl profile and moderate umbilicus; ornamentation consisting of concavo-convex growth lines and sharp elongate umbilical nodes.

M a t e r i a l. Three steinkerns from stratigraphic levels 3 and 5a of the Mospyne Formation.

D e s c r i p t i o n. Specimen IGSU-7/3254 is an almost fully preserved steinkern of 9.1 mm diameter with convex venter; it merges imperceptibly into almost flat flanks, which weakly converge onto the ventrolateral shoulder; the umbilical margin is rectangular and umbiblicus is moderate (uw/dm = 0.32). Ornamentation consisting of frequent clearly visible growth lines. These form a shallow external sinus and a low projection on the ventrolateral shoulder and very shallow, broad sinus on the flank. The surface of the umbilical margin is covered with sharp nodes, spaced approximately 0.35 to 0.40 mm apart at conch diameter 9.1 mm. Two weak concavo-convex constrictions with high ventrolateral projection and very shallow ventral sinus are prominent on whorl. The suture line is not preserved.

R e m a r k s. The described species differs from other representatives of the genus in its more delicate ornamentation and the narrower umbilicus. Gastrioceras kutejnikovense is very similar to Gastrioceras magoffinense (early Atokan; Kentucky, USA). As the suture line of Gastrioceras kutejnikovense is not known, I cannot at present confidently compare these taxa; the conch morphology of these species is very similar.

O c c u r r e n c e. Late Bashkirian, Mospyne Formation (sandstone and shale bellow the G 1 2 limestone layer to the G 4 limestone layer); Donets Basin ( Ukraine).

Figures

Text-fig. 9. Ammonoids from the Mospyne Formation. a–d: Gastrioceras angustum PATTEISKY, 1964, lateral view (a, c), ventral view (b, d); a, b – specimen IGSU-7/8100, c, d – specimen IGSU-7/669b. e–i: Gastrioceras lupinum POPOV, 1979, lateral view; e – specimen IGSU-4/687, f – specimen IGSU-4/687a, g – specimen IGSU-4/687b, h – specimen IGSU-4/644, i – specimen IGSU-4/1516. j, k: Gastrioceras kutejnikovense POPOV, 1979, lateral view; j – specimen IGSU-7/3254, k – specimen IGSU-7/3254a. Scale bar 5 mm.