Listrognathosuchus
Introduction '''''Listrognathosuchus''''' is an extinct genus of alligatoroid crocodilian. Fossils date back to the middle Paleocene epoch. In 1997, the generic name replaced that of ''Leidyosuchus'' for the species ''L. multidentatus'' (now the type species of ''Listrognathosuchus''). ''"L." multidentalis'' was first described by Charles Mook in 1930 on the basis of the holotype AMNH 5179, consisting of a partial vertebral column, mandible, partial left ilium, and left tibia, found from a locality in Torrejon Arroyo, New Mexico (then referred to as the Torrejon beds, and now thought to be part of the Nacimiento Formation).
Phylogenetics The fragmentary nature of the material referable to ''Listrognathosuchus'' have made it hard to classify within Crocodylia, but it is now thought to be a relatively basal alligatoroid. ''Listrognathosuchus'' is closely related to ''Borealosuchus'', a more basal eusuchian that is not an alligatoroid, but rather a close relative of a monophyletic group of which the superfamilies Alligatoroidea and Crocodyloidea comprise. In fact, ''Borealosuchus'' was first used as a replacement name for four species of ''Leidyosuchus'', the same genus that ''Listrognathosuchus multidentatus'' once belonged to. Prior to the reassessment of ''Leidyosuchus'' in 1997, many relationships for the genus within Crocodilia have been considered. It was suggested to be a possible member of Diplocynodontinae or a relative of later crocodylids, and even as a member of its own subfamily of broad snouted early eusuchians, Leidysuchinae. However, with the naming of ''Listrognathosuchus'' and ''Borealosuchus'', most species previously assigned to ''Leidyosuchus'' are now believed to have had little relation to any of the mentioned crocodilians.
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