Hosholmoceras, Kröger, 2025

Genus Hosholmoceras gen. nov.

urn:lsid:zoobank.org:act:67E22CEA-BE72-42D4-9847-5F0A216039FC

Type species

Hosholmoceras ovalis gen. et sp. nov. from Hosholm shore, Vormsi Island, Estonia, Adila Formation, Pirgu Regional Stage.

Diagnosis

Endogastrically curved brevicones with very short chambers (RCL ca 0.05–0.07); conch cross section compressed or subtriangular; in lateral view mature conch slightly gibbous with largest conch heights near the base of the mature phragmocone; mature body chamber short, simple conical; sutures with shallow lateral lobes; siphuncle marginal, small; siphuncular segments rounded, expanded; septal necks cyrtochoanitic; endosiphuncular bulettes occur.

Etymology

Hosholm is the type locality of this genus.

Comparison

This genus is superficially similar to Hemibeloitoceras Balashov, 1962b , in having very short chambers (RCL ca 0.08) and a relatively thin, marginal siphuncle with simple expanded siphuncular segments. However, the conch of Hemibeloitoceras is exogastrically curved, expands gradually and is slenderer (angle of expansion ca 8°) while the sutures are directly transverse without a lateral lobe. Another curved breviconic form with very short chambers is Antiphragmoceras Foerste, 1925 . This also differs from Hosholmoceras gen. nov. in having an exogastrically curved conch.