Gastrioceras angustum PATTEISKY , 1964

Dernov, Vitaly, 2022, Late Bashkirian Ammonoids From The Mospyne Formation Of The Donets Basin, Ukraine, Fossil Imprint 78 (2), pp. 489-512 : 501-502

Gastrioceras angustum PATTEISKY, 1964

Text-fig. 9a–d

1831 Ammonites subcrenatus ; Münster, p. 371, pl. 8, fig. 1. [nomen nudum]

1897 Gastrioceras carbonarium ; Foord and Crick, p. 229, fig. 110 (pars).

1914 Gastrioceras carbonarium ; Pruvost, p. 16.

1929 Gastrioceras subcrenatum ; Schmidt, pl. 19, figs 17, 18.

1931 Gastrioceras subcrenatum ; Dorlodot and Delépine, p. 73, figs 10–13c.

1938 Gastrioceras subcrenatum ; Demanet and van Straelen, p. 183, fig. 59.

1964 Gastrioceras carbonarium angustum ; Patteisky, p. 650, pl. 1, figs 10–13, 15.

1965 Gastrioceras carbonarium angustum ; Patteisky, p. 20, pl. 7, figs 12–15, pl. 8, figs 1–3.

1965 Gastrioceras carbonarium carbonarium ; Patteisky, p. 19, pl. 7, fig. 4.

1997 Gastrioceras angustum ; Korn, p. 89, pl. 15, fig. 7.

2007 Gastrioceras angustum ; Korn, p. 29, figs 17, 18.

H o l o t y p e. Specimen BB.P223.WB in the Deutsches Bergbau-Museum (Bochum, Germany); figured by Korn (2007: fig. 17В).

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. Hammertal, Plessbach pit (near Bochum-Stiepel, Rhenish Massif, Germany); marine horizon above Sarnsbank 2 coal seam, G2 Zone (base of Langsettian).

D i a g n o s i s. Gastrioceras with thickly discoidal, almost pachyconic conch with convex venter, weakly convex flanks and moderate umbilicus covered with nodes. Flanks bearing lamellae; four weak concavo-convex constrictions are prominent on each whorl.

M a t e r i a l. Six steinkerns of the very small conchs (dm = 5.5–8.5 mm) from stratigraphic levels 3 and 8 of the Mospyne Formation.

D e s c r i p t i o n. Specimen IGSU-4/669b (Textfig. 9c, d) is an almost fully preserved steinkern of 8 mm diameter. The conch is thickly discoidal, almost pachyconic (ww/dm = 0.59) with moderate umbilicus (uw/dm = 0.36), moderately depressed (ww/wh = 1.80), semi-circular whorl profile and wide convex venter; ventrolateral shoulder is rounded; flanks are weakly convex; umbilical margin angular. Ornamentation with umbilical nodes and lateral lamellae, forming a narrow shallow sinus on the venter, a low projection on the ventrolateral shoulder and narrow shallow sinus on the flank. Four weak concavo-convex constrictions with high ventrolateral projection and very shallow ventral sinus are prominent on the whorl. The suture line is not preserved on the material studied.

Specimen IGSU-4/669b ( Text-fig. 9a, b ) is an almost fully preserved steinkern of 6.5 mm diameter. The conch is thickly discoidal (ww/dm = 0.51) with moderate umbilicus (uw/dm = 0.31), moderately depressed (ww/ wh = 1.50), semi-circular whorl profile and wide convex venter; ventrolateral shoulder is rounded; flanks are weakly convex; umbilical margin angular; umbilical wall flattened and wide. Ornamentation with umbilical nodes and lateral lamellae, forming a narrow shallow sinus on the venter, a low projection on the ventrolateral shoulder and narrow shallow sinus on the flank. On the midflank the lamellae are spaced about 0.4 to 0.5 mm apart. Four weak concavoconvex constrictions with high ventrolateral projection and very shallow ventral sinus are prominent on the whorl. The suture line is not preserved on the material studied.

R e m a r k s. Gastrioceras angustum differs from G. listeri in the lack of spiral lines between the umbilical nodes, less coarse umbilical nodes, less depressed whorl profile, and from G. circumnodosum in the much lower number of umbilical nodes.

O c c u r r e n c e. Basal part of the Westphalian of Germany, Great Britain, and south Portugal.

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.