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.

Figures

Fig. 8(preceding page). Median sections of phragmocones of ActinoceridaTeichert, 1933 of the Vormsi– Pirgu regional stages, Estonia. A–B. Nybyoceras bekkeri Troedsson, 1926. A. Specimen GIT 426-1107 from Paluküla quarry, Vormsi Regional Stage. B. Specimen GIT 426-1120 from Kasari, Vormsi Regional Stage. C–D, G. Nybyoceras intermedium Teichert, 1930. C. Specimen GIT 426-573 from Paluküla quarry, Vormsi Regional Stage. D. Specimen TUG 939-50 from Kõrgessaare quarry, Hiiumaa Island, Vormsi Regional Stage. E. Ormoceras heckeri Teichert, 1930, specimen TUG 1680-19 from Saxby shore, Vormsi Island, Vormsi Regional Stage. F. Gorbormoceras vohilaidense gen. et sp. nov., holotype GIT 878-235, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage. G. Specimen TUG 1745- 293 from Pahkla, Pirgu Regional Stage. H. Ormoceras sp., specimen TUG 1745-239 from Salu, Pirgu Regional Stage. Scale bars = 10 mm for all figures, same scale in A–C, and in D–G.