Original paper

Acanthoteuthis problematica Naef, 1922, an almost forgotten taxon and its role in the interpretation of cephalopod arm armatures

Fuchs, Dirk; Heyng, Alexander M.; Keupp, Helmut

Abstract

A new belemnoid genus, Winkleriteuthis, is introduced for Acanthoteuthis problematica Naef, 1922 from the Lower Tithonian Plattenkalks of Daiting and Eichstätt. Winkleriteuthis lacks a solid rostrum proper and mainly differs from other rostrum-less belemnoids such as phragmoteuthids, belemnoteuthids and diplobelids by its unusual proostracum and hook shape. Phylogenetic relationships are therefore obscure. Both Naef (1922) and Jeletzky (1966) briefly discussed Acanthoteuthis problematica in the light of the cephalopod arm equipment. A review of our present knowledge about coleoid arm armatures shows that 1) all coleoid subgroups including extinct belemnoids possessed suckers, 2) Mesozoic gladius-bearing vampyropods were devoid of both sucker rings and hooks, 3) belemnoid and decabrachian hooks represent convergent developments, and 4) belemnoid hooks (onychites), vampyropod cirri and decabrachian trabeculae are homologous arm structures.

Keywords

coleoideatithonianeichstÄttsuckersarm hooks