New brevirostrines (Crocodylia, Brevirostres) from the Upper Cretaceous of China

Abstract

A new alligatoroid, Eurycephalosuchus gannanensis gen. et sp. nov. and an undetermined brevirostrine, Brevirostres gen. et sp. indet. are described. They are preserved together in the Upper Cretaceous of Jiangxi Province, China. Eurycephalosuchus gannanensis is established based on a well-preserved skull with the mandible and some postcranial elements, and Brevirostres gen. et sp. indet. is represented by the right scapula and coracoid. Eurycephalosuchus gannanensis is assigned to Alligatoroidea and phylogenetically nested within a sub-group of Orientalosuchina with other four genera from China and Vietnam. Eurycephalosuchus gannanensis differs from all other orientalosuchines primarily in the short and broad appearance of its skull, the abnormally short (anteroposteriorly narrow) skull table, the exclusion of the parietal from the occipital ridge posteriorly, the postdentary part of the mandible much deeper than the anterior part dorsoventrally, the splenial excluded from the mandibular symphysis, and the external mandibular fenestra small and nearly vertical in orientation. It is different from Brevirostres gen. et sp. indet. in that the distal end of the scapular blade is relatively broader, and the anterior margin of the coracoid is more concave in addition to the smaller size. The discovery of the two new forms not only enriches the diversity of the local fauna but also confirms the monophyly of Orientalosuchina and the Asian dispersal event of the clade after diverging from the mainline rather than a sub-lineage of Alligatoroidea in the Late Cretaceous.