A reassessment of the morphology and taxonomic status of 'Crocodylus'depressifrons Blainville, 1855 (Crocodylia, Crocodyloidea) based on the Early Eocene remains from Belgium

Abstract

The name Crocodilus depressifrons appears in the literature as the caption of a table, published by Blainville in 1855, depicting crocodylian remains from France. Although a proper diagnosis and description have never been published, this species has been frequently used to identify some European Eocene crocodyloids with a generalized, not elongated, rostrum. In the last 50 years, C. depressifrons has been often referred to the genus Asiatosuchus. This genus, erected by Mook in 1940 on the basis of fossil remains from the Middle Eocene of Mongolia, actually contains a rich and apparently nonmonophyletic assemblage of Palaeogene crocodyloids. In order to help clarify the morphology and the relationships of the Asiatosuchus-like taxa, it is here described a rich collection of crocodyloid remains, including skulls and a nearly complete skeleton, from four different Early Eocene localities of the Belgian Tienen Formation: Dormaal, Erquelinnes, Leval, and Orp-le-Grand. All these remains belong to one single taxon which clearly represents the long known but never properly described 'C.'depressifrons. They allow, for the first time, the diagnosis this species on the basis of an unequivocal set of characters, contributing to the long awaited revision of the Asiatosuchus-like taxa.