Discoceras undetermined

Discoceras sp. indet. Figs 23, 28 Material examined GERMANY • 1 spec.; Britz (Berlin); Haljala Regional Stage (Sandbian Stage); Neben Coll.; illustrated in Fig. 28; MB.C.32328. Description Specimen MB.C.32328 is a coiled phragmocone with a diameter of 72 mm; it consists of two and a half whorls (Fig. 28). At its largest diameter, the conch is thinly discoidal (CWI = 0.32) and evolute (UWI = 0.50) with a high coiling rate (WER = 2.02). The whorls are not imprinted dorsally; the whorl profile is weakly depressed (WWI = 1.08) and weakly subquadratic with rounded venter and slightly flattened flanks. The phragmocone chamber length (RCL) is 0.24 in the last half whorl. The suture line has a shallow lateral lobe and it is straight on the venter. The siphuncle is very close to or in contact with the dorsal shell wall; its diameter cannot be measured exactly, but it appears to be about 0.25 of the corresponding whorl height. The shell ornament consists of fairly regularly spaced, flat annuli accompanied by fine lirae, which extend in a rather deep ventral sinus; on the internal mould, the annuli are rounded. The inner whorls of the conch cannot be measured and appear to be asymmetrically coiled but this is probably the result of inaccurate preparation or gluing by previous researchers. Remarks Specimen MB.C.32328 has an incomplete aperture and it is not possible to determine the size of the adult conch or whether the last whorl and body chamber were uncoiled. Its geometry is rather similar to that in the holotype of Discoceras aseriense sp. nov. (GIT 225-1084). The latter differs from specimen N 21 in the whorl profile at dm = 70 mm; it is more flattened from the ventral side and has convex flanks (vs weakly subquadrate with rounded venter and slightly flattened flanks in MB.C.32328). Despite the similarities, specimen MB.C.32328 is kept in open nomenclature, since it is rather incompletely preserved and also significantly younger stratigraphically (Haljala vs Aseri regional stages).