Eothoracosaurus

Eothoracosaurus (meaning "dawn Thoracosaurus") is an extinct monospecific genus of eusuchian crocodylomorphs found in Eastern United States which existed during the Late Cretaceous period. Eothoracosaurus is considered to belong to an informally named clade called the "thoracosaurs", named after the closely related Thoracosaurus. Thoracosaurs in general were traditionally thought to be related to the modern false gharial, largely because the nasal bones contact the premaxillae, but phylogenetic work starting in the 1990s instead supported affinities within gavialoid exclusive of such forms. Even more recent phylogenetic studies suggest that thoracosaurs might instead be non-crocodilian eusuchians.

==Discovery and naming== Fossils are known from the Ripley Formation in Mississippi and date back to the early Maastrichtian stage of the Late Cretaceous. Some fragmentary material from the Coon Creek Formation of western Tennessee dating back to the late Campanian (slightly older than the specimens from Mississippi) has been referred to Eothoracosaurus as well. The holotype specimen of Eothoracosaurus (MSU 3293, a skull and associated postcrania in the collection of the university's Dunn-Seiler Museum) was originally discovered in 1931 and first described by Kenneth Carpenter in 1983 and initially referred to Thoracosaurus neocesariensis. The material was eventually reexamined by Christopher Brochu in 2004, taking note of substantial differences to other thoracosaurs and finding them severe enough to warrant a separate genus: Eothoracosaurus.