“Onychoteuthis” Conocauda Quenstedt, 1849 (Cephalopoda: Coleoidea)

N. Jb. Geol. Paläont. Abh. 270/3 (2013), 245–255 Article Stuttgart, December 2013

Taxonomic revision of “Onychoteuthis” conocauda Quenstedt, 1849 (Cephalopoda: Coleoidea)

Dirk Fuchs, Desmond T. Donovan and Helmut Keupp With 5 figures

Abstract: For Phragmoteuthis conocauda (Quenstedt, 1849) from the Lower Toarcian Posidonia Shale (South Germany) and Phragmoteuthis montefiorei (Buckman, 1880) from the Upper Sinemu- rian Charmouth Mudstone Formation (Dorset, UK), a new belemnoid genus, Clarkeiteuthis, is in- troduced. Clarkeiteuthis significantly differs from Phragmoteuthis by the absence of a three-lobed proostracum as well as the possession of a unique hook shape. Owing to the presence of a proostracum, which is significantly narrower than in belemnotheutids, Clarkeiteuthis is accommodated within the Diplobelida. This taxonomic revision has an influence on our previous knowledge about the Phragmoteuthida. The taxon already disappeared after the Sinemurian (instead of Toarcian). Hence, the youngest known representative of the Phragmoteuthida is Phragmoteuthis huxleyi donova n, 2006. The true number of arms, which was originally based on the ten arms of Clarkeiteuthis conocauda, is still unknown in phragmoteuthid belemnoids. The new assignment of Clarkeiteuthis conocauda and Clarkeiteuthis montefiorei induces the presence of hooklets (onychites) within the Diplobelida, which was previously questioned.

Key words: Coleoidea, Diplobelida, Clarkeiteuthis nov. gen., taxonomy, Lower Jurassic.

1. Introduction count of the hook-bearing arms. He listed it following Belemnoteuthis montefiorei Buckman, 1880, which he In his monograph ‘Die Cephalopoden’ Quenstedt also assigned to Acanthoteuthis, and illustrated arm (1845-1849) described several fossil coleoid cephalo- hooks of the two species (1922: fig. 68g, h) but did not pods from the Posidonienschiefer Formation (Jurassic, comment on their similarity. naef regarded Acantho- Lower Toarcian) of the Swabian Alb. Apart from the teuthis as a ‘fiktive Gattungsbezeichnung’ (fictitious belemnites, these were placed in Recent coleoid gen- generic name) perhaps because he was uncertain of the era, as was the practice of most authors at that time. affinities of the species that he placed in it. Onychoteuthis conocauda was included in the Recent For Jeletzky (1966), both taxa under discussion squid genus, which has hook-bearing arms, because it were apparently of minor importance since there is also possessed arm hooks, despite the fact that it also not a single mention on “Onychoteuthis” conocauda has a mineralized phragmocone, whereas Onycho- and only a few words on the arm crown of “Belemno- teuthis had a chitinous gladius. teuthis” montefiorei (p. 138). naef (1922: 179) placed Quenstedt’s species in the donova n (1977: 21) was misled into including fos- belemnoid genus Acanthoteuthis, no doubt also on ac- sils now placed in Belemnoteuthis montefiorei (Buck-