Osteology and relationships of Libanopycnodus wenzi gen. et sp. nov. and Sigmapycnodus giganteus gen. et sp. nov. (Pycnodontiformes) from the late cretaceous of Lebanon

Abstract

The skeleton and the relationships of Libanopycnodus wenzi gen. et sp. nov. and of Sigmapycnodus giganteus gen. et sp. nov., two pycnodontiform fishes from the marine Cenomanian (Late Cretaceous) of Lebanon, are studied in detail. Both species belong to the family Pycnodontidae, as shown by their parietal brush-like process. Some osteological characters (bifid cloacal scale, large well visible dilatator fossa surrounded by the dermosphenotic and the dermopterotic, etc.) indicate that they are members of the subfamily Pycnodontinae. Libanopycnodus gen. nov. has the preopercle much deeper than the exposed region of the hyomandibula-dermohyomandibula and is the most primitive genus of this lineage. Sigmapycnodus gen. nov. is one of the most advanced members of the subfamily. It shares with Oropycnodus Poyato-Ariza & Wenz, 2002 and Pycnodus Agassiz, 1833 an apomorphy not present in the less specialized Pycnodontinae, the arcocentra in hypercomplex contact.