Gastrioceras lupinum POPOV , 1979

Dernov, Vitaly, 2022, Late Bashkirian Ammonoids From The Mospyne Formation Of The Donets Basin, Ukraine, Fossil Imprint 78 (2), pp. 489-512 : 502-503

Gastrioceras lupinum POPOV, 1979

Text-fig. 9e–i

1979 Gastrioceras lupinum ; Popov, p. 83, pl. Х, figs 9–11.

2018 Gastrioceras lupinum ; Dernov, p. 9, pl. 6, fig. 1.

H o l o t y p e. Specimen VSEGEI- 3223 in the Russian Geological Research Institute (St. Petersburg, Russia); figured by Popov (1979: pl. X, fig. 9).

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. Sorocha Ravine, Donets Basin, Ukraine; Smolyanynivka or Belaya Kalitva Formation (Н 5 or І 1 limestone layer; late Bashkirian).

D i a g n o s i s. Gastrioceras with involute pachyconic conch with moderately depressed whorl profile, strongly convex venter, slightly convex flanks and very narrow and moderate umbilicus covered with small sharp nodes. Flanks bearing thin concavo-convex ribs; three constrictions are prominent on each whorl.

M a t e r i a l. 11 fragments of steinkerns and conch impressions from stratigraphic level No. 8 in the upper part of the Mospyne Formation.

D e s c r i p t i o n. The most well-preserved specimen IGSU-4/687 ( Text-fig. 9e ) is pachyconic (ww/dm = 0.70 at conch diameter 9.4 mm) with moderate umbilicus (uw/ dm = 0.34) and convex venter. The flanks are almost flat and weakly converge towards the ventrolateral shoulder. The umbilical margin is rectangular; the umbilical wall is vertical. The whorl profile is moderately depressed (ww/wh = 1.47 at conch diameter 9.4 mm and 1.60 at conch diameter 30.0 mm). The surface of the conch is covered with small sharp umbilical nodes and thin transverse ribs, forming a shallow external sinus, a low ventrolateral projection and a very shallow, wide lateral sinus. Three prominent constrictions are present on each whorl.

R e m a r k s. Gastrioceras lupinum differs from Gastrioceras araium and G. magoffinense in the coarser ornamentation. Gastrioceras lupinum is distinguished from G. formosum by the conch form (ww/dm = 0.53 at conch diameter 30 mm in the Gastrioceras lupinum holotype but 0.86 at conch diameter 30 mm in G. formosum ), the narrower whorl profile (ww/wh = 1.60 at conch diameter 30 mm in Gastrioceras lupinum holotype but 2.22 in G. formosum ) and the presence of lateral ribs in Gastrioceras lupinum .

O c c u r r e n c e. Late Bashkirian, upper part of the Mospyne Formation to basal layer of the Belaya Kalitva Formation; 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.