3D skull modelling and description of a new baurusuchid (Crocodyliformes, Mesoeucrocodylia) from the Late Cretaceous (Bauru Basin) of Brazil

Abstract

Baurusuchidae is one of the most diverse groups of South American notosuchians, recorded in Late Cretaceous deposits of Brazil and Argentina. The group is characterized by a reduced tooth formula, a lateromedially compressed rostrum, and a verticalized quadrate, representing the top predators of their faunas. The morphology of the skull is historically the most employed tool to investigate the phylogeny of baurusuchids, as most of the species have been described based primally on cranial remains. The present study describes a new baurusuchid species from the Bauru Basin of Brazil, discussing its phylogenetic position within the group. Furthermore, the study provides the first tridimensional digital reconstruction of individual skull bones for Notosuchia. The new species differs from all the other known baurusuchids by a depression on the posterior portion of nasal bearing a crest, a infraorbital crest of the jugal that extends until the anterior margin of the lacrimal, the absence of a longitudinal crest or depression on the dorsal surface of the frontal, and the lateral convexity of the squamosal prongs taking part of the occipital wall. The new taxon is consistently positioned as sister to a clade including all other baurusuchines, but the relations among Aplestosuchus sordidus, Baurusuchus albertoi, and Stratiotosuchus maxhechti remain unresolved. The phylogenetic data matrix includes newly proposed characters, which hep in the differentiation between Baurusuchinae and Pissarrachampsinae. Yet, the new species shares morphological features with both groups, suggesting the occurrence of "Zones of Variability" in the origin of Baurusuchidae.