Stockumites sp.

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Gattendorf (Devonian-Carboniferous boundary; Upper Franconia, Germany), European Journal of Taxonomy 883, pp. 1-61 : 38

Stockumites sp.

Fig. 21

Material examined

GERMANY • 5 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21a (“ Gattendorfia Limestone ”); Korn 1989 Coll.; MB.C.31271– MB.C.31275 • 180 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21 (“ Gattendorfia Limestone ”); Schindewolf 1934 Coll.; BGRB unnumbered • 22 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21a (“ Gattendorfia Limestone ”); Korn 1989 Coll.; MB.C.31276.1–22 • 8 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21c–d (“ Gattendorfia Limestone ”); Korn 1989 Coll.; MB.C.3127.1–8 • 2 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21f (“ Gattendorfia Limestone ”); Korn 1989 Coll.; MB.C.31278.1–2 • 1 specimen; Upper Franconia , 400 m north-west of Kirchgattendorf; bed; Weyer 1995 Coll.; MB.C.31279 • 7 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21e; Weyer 1995 Coll.; MB.C.31280.1–7 • 2 specimens; Upper Franconia , 400 m north-west of Kirchgattendorf; bed 21f; Weyer 1995 Coll.; MB.C.31281.1–2 .

Description

From the many specimens that cannot be determined more precisely, five small examples are shown here ( Fig. 21 ), which show different juvenile morphologies. Specimens MB.C.31271 and MB.C.31272 ( Fig. 21A–B ) already have an almost completely involute conch in the early stage; both possess lamellar growth lines running with a concave arc across the flank. Constrictions are not present on either specimen. In contrast to the two previously described specimens, the three other specimens MB.C.31273– MB.C.31275 ( Fig. 21C–E ) show an open umbilicus with a conch diameter of 6 mm (uw/dm about 0.25). While specimenMB.C.31273 appears largely smooth, specimens MB.C.31274 and MB.C.31275 have quite strong growth lines that run along the flank with a concave arc and form a sinus on the venter. Both specimens have faint constrictions in the shell.

Figures

Fig. 21. Stockumites sp., juvenile specimens (Korn 1989 Coll.) from Gattendorf, bed 21a. A. Specimen MB.C.31271. B. Specimen MB.C.31272. C. Specimen MB.C.31273. D. Specimen MB.C.31274. E. Specimen MB.C.31275. Scale bar units= 1 mm.