A primitive marine gavialoid from the paleocene of Morocco

The discovery of a new genus and species of gavialoid at the Danian-Thanetian boundary, in the Oulad Abdoun Basin of Morocco, is consistent with an African origin of Gavialoidea. Argochampsa krebsi, n.g. n.sp., exhibits a particular shape of the anterior end of its premaxillae, transversely broad and strongly bent downwards, a shape found in distantly related taxa, such as pholidosaurids and Terminonaris. A phylogenetic analysis, suggests that A. krebsi is a primitive gavialoid, placed with Eogovialis africanum between 'thoracosaurs' (primitive Gavialoidea) and more derived taxa. This analysis supports the previous morphological analysis, which suggests a close relationship of Tomistominae with Crocodylinae, in contrast with the molecular analysis which give a closer relationships between Tomistoma and Gavialis. The marine nature of the layer where Argochampsa comes from is consistent with a marine origin for Argochampsa. This demonstrates the existence of marine adaptation in fossil species of primitive gavialoids, which may explain the dispersal of the fossil gavialoids to South America and Asia during and after the Oligocene.