The first occurrence of Acresuchus (Alligatoroidea, Caimaninae) from the Urumaco Formation of Venezuela and the late Miocene crocodylian fauna of northern South America

Abstract

The late Miocene Urumaco Formation of Venezuela has one of the richest and ecologically diverse crocodylian fossil faunas of the Cenozoic of South America. This diversity includes several different genera and species of crocodylians that held many distinct ecological niches, such as those of generalist predators, durophagous predators, giant predators and longirrostrine piscivorous, among others. This paper offers a significant addition to this already remarkable fauna by describing the first occurrence of Acresuchus pachytemporalis Souza-Filho et al.,2018 for the Urumaco Formation. This record consists of the specimen MCNUSB-PB-02FU-RS43, which is a posterior portion of the skull, consisted mostly by the skull table and the braincase, with incomplete mandibular rami associated. The specimen also represents the first occurrence of A. pachytemporalis outside the late Miocene Solimões Formation of Brazil, from which it has been originally described. As such, the occurrence of A. pachytemporalis in the Urumaco Formation recorded by this contribution is another evidence of the large taxonomical and paleoecological similarity between the crocodylian faunas of this unit and the Solimões Formation, which share many similar taxa at generic and specific levels and exhibit similar ecological niches being hold by fossil crocodylians.