?Brachychampsa sealeyi, sp nov., (Crocodylia, Alligatoroidea) from the Upper Cretaceous (lower Campanian) Menefee Formation, northwestern New Mexico

Abstract

?Brachychampsa sealeyi sp. nov. is a small alligatoroid based on a partial skull, associated partial mandible, and a dorsal? osteoderm from the Upper Cretaceous (lower Campanian) Menefee Formation, northwestern New Mexico. The holotype of ?B. sealeyi is the oldest of four documented Late Cretaceous alligatoroid skulls. ?Brachychampsa sealeyi differs from Brachychampsa montana, Albertochampsa langstoni, and other alligatoroids primarily in having an anteriorly tapering rostrum with a relatively reduced anterior dentition and smaller narial and incisive openings but relatively larger and more bulbous posterior teeth. The single associated osteoderm has a longitudinal keel and surfaces for articulation with overlapping osteoderms. Cladistic analysis suggests that ?B. sealeyi is a sister taxon to B. montana and supports the hypothesis that Brachychampsa and Albertochampsa form a monophyletic clade outside the Alligatoridae. Punctures on the mandible suggests that a bite was inflicted by another alligator.