Ormoceras sp. A

Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, European Journal of Taxonomy 978, pp. 1-169 : 21

Ormoceras sp. A

Fig. 8H

Material examined

ESTONIA • 1 spec.; Salu; Pirgu Regional Stage; TUG 1745-239 .

Description

Specimen TUG 1745-239 is a ca 113 mm long fragment of a phragmocone with a conch height of 23– 45 mm (angle of expansion = 11°) which is slightly deformed. The conch surface is apparently smooth. The RCL varies between 0.23–0.24 and at a conch height of 27 mm the RSP is ca 0.3. The septal necks are short adnate, and the connecting ring forms barrel-shaped siphuncular segments with a height of 5.8 mm where the length is 6.5 mm (SCR = 0.89). Incipient, symmetric endosiphuncular annuli occur where the conch height is 25 mm.

Remarks

The specimen differs from O. heckeri in having a less expanded siphuncle (SCR = 0.89 in specimen TUG 1745-239 compared with SCR> 1 in O. heckeri ) at comparable conch diameters. However, this single, fragmentarily preserved specimen does not allow for species level determination and detailed comparison with other, e.g., North American species of the genus.