Article: A new alligator from the Upper Cretaceous of Canada and the relationships of early eusuchians

A new alligatorine eusuchian, Stangerochampsa mccabei gen. et sp. nov., is described on the basis of a partial skeleton from the Horseshoe Canyon Formation (Early Maastrichtian) of southern Alberta. It is unique in possessing an ectopterygoid/palatine contact, a ventrolateral process of the quadrate, a groove-like recess for nerves and blood vessels in the upper jaw, a rectangular palatine with a lateral process at its midpoint, and a basioccipital with a ventral exposure longer than that of the pterygoid. Several derived characters indicate a close relationship of S. mccabei with two Late Cretaceous alligatorines, Brachychampsa montana and Albertochampsa langstoni. A preliminary phylogenetic analysis, based on 46 characters of selected taxa, leads to the hypothesis that Leidyosuchus, rather than Hylaeochampsa, is the most primitive eusuchian, supports the monophyly of the Alligatorinae (with the exclusion of Prodiplocynodon), and suggests that the Alligatorinae may consist of at least two distinct assemblages.