Taxonomic revision of “Onychoteuthis” conocauda QUENSTEDT, 1849 (Cephalopoda: Coleoidea) Dirk Fuchs, Desmond T. Donovan and Helmut Keupp With 5 igures Abstract: For Phragmoteuthis conocauda ( Quenstedt, 1849) from the Lower Toarcian Posidonia Shale (South Germany) and Phragmoteuthis monteiorei (Buckman, 1880) from the Upper Sinemu- rian Charmouth Mudstone Formation (Dorset, UK), a new belemnoid genus, Clarkeiteuthis, is in- troduced. Clarkeiteuthis signiicantly 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 proost- racum, which is signiicantly narrower than in belemnotheutids, Clarkeiteuthis is accommodated within the Diplobelida. This taxonomic revision has an inluence 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 dono- van, 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 monteiorei 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 In his monograph ‘ Die Cephalopoden’ Quenstedt (1845-1849) described several fossil coleoid cephalo- pods from the Posidonienschiefer Formation (Jurassic, Lower Toarcian) of the Swabian Alb. Apart from the belemnites, these were placed in Recent coleoid gen- era, as was the practice of most authors at that time. Onychoteuthis conocauda was included in the Recent squid genus, which has hook-bearing arms, because it also possessed arm hooks, despite the fact that it also has a mineralized phragmocone, whereas Onycho- teuthis had a chitinous gladius. naef (1922: 179) placed Quenstedt’ s species in the belemnoid genus Acanthoteuthis, no doubt also on ac- count of the hook-bearing arms. He listed it following Belemnoteuthis monteiorei Buckman, 1880, which he also assigned to Acanthoteuthis, and illustrated arm hooks of the two species (1922: ig. 68g, h) but did not comment on their similarity. naef regarded Acantho- teuthis as a ‘iktive Gattungsbezeichnung’ ( ictitious generic name) perhaps because he was uncertain of the afinities of the species that he placed in it. For Jeletzky (1966), both taxa under discussion were apparently of minor importance since there is not a single mention on “ Onychoteuthis” conocauda and only a few words on the arm crown of “ Belemno- teuthis” monteiorei (p. 138). donovan (1977: 21) was misled into including fos- sils now placed in Belemnoteuthis monteiorei (Buck- ©2013 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany www.schweizerbart.de DOI: 10.1127/0077-7749/2013/0368 0077-7749/2013/0368 $ 2.75 N. Jb. Geol. Paläont. Abh. 270/3 (2013), 245–255 Article Stuttgart, December 2013 eschweizerbart_xxx