Osteology of Eubiodectes libanicus (Pictet & Humbert, 1866) and some other ichthyodectiformes (Teleostei): phylogenetic implications

摘要

The osteology of the ichthyodectiform Eubiodectes libanicus (Pictet & Humbert, 1866) from the Cenomanian of Lebanon is described on the basis of acid-prepared specimens. For comparative purposes, the osteology of other putative ichthyo-dectiforms is described or discussed. We focus on the description of hitherto poorly described species such as Chiromystus mawsoni Cope, 1885, Ghrisichthys bardacki (Cavin, 1997a), 'Saurodon' intermedius (Newton, 1878) and Thrissops sp. from Kimmeridge, England. Sixty-nine morphological characters are defined and analysed to infer the phylogenetic relationships within ichthyodectiforms. The main results are: (1) exclusion of Ascalabothrissops and Pachythrissops from the ichthyodectiforms; (2) redesignation of'Ichthyodectes' bardacki, from the Turonian of Morocco, to Ghrisichthys gen. nov.; (3) resolution of a monophyletic family Cladocyclidae grouping mid-Cretaceous ichthyodectiforms that lived mainly along the southern margin of Tethys (Chirocentrites, Cladocyclus, Eubiodectes, Chiromystus); (4) resolution of a Late Cretaceous family Ichthyodectidae containing Ichthyodectes, Ghrisichthys and Xiphactinus from mid-northern latitude seas; and (5) a better resolved Late Cretaceous family Saurodontidae in the northern hemisphere, that includes the genus Gillicus.