Stangerochampsa

Stangerochampsa is an extinct genus of globidontan alligatoroid, possibly an alligatorine or a stem-caiman, from the Late Cretaceous of Alberta. It is based on RTMP.86.61.1, a skull, partial lower jaws, and partial postcranial skeleton discovered in the late Campanian–early Maastrichtian-age Horseshoe Canyon Formation. Stangerochampsa was described in 1996 by Wu and colleagues. The type species is S. mccabei. The generic name honors the Stanger family, the owners of the ranch where the specimen was found, and the species name honors James Ross McCabe, who discovered, collected, and prepared it. Stangerochampsa is described as "small to medium–sized"; the type skull is long from the tip of the snout to the occipital condyle, and is wide at its greatest, while the thigh bone is long. It had heterodont dentition, with large crushing teeth at the rear of the jaws. Wu and colleagues, using phylogenetic analyses, found their new genus to be closest to Brachychampsa, and then Albertochampsa and Hylaeochampsa successively, as part of a clade within Alligatorinae that also included Allognathosuchus, Ceratosuchus, and Wannaganosuchus. This arrangement also unites most Mesozoic and Paleogene alligatorines. Brochu (1999), in an analysis of all alligatoroids, found Stangerochampsa and Brachychampsa to be just outside Alligatoridae, and suggested that Stangerochampsa and Albertochampsa were synonymous. Brochu (2004) and Hill and Lucas (2006) also found Stangerochampsa to be outside of Alligatorinae; Hill and Lucas found Albertochampsa to its sister taxon. Below is a cladogram based on the results of a 2018 tip dating study by Lee & Yates that simultaneously used morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data, which shows Stangerochampsa's placement within Globidonta. On the other hand, in the phylogenetic analysis conducted by Bona et al. (2018) Stangerochampsa was recovered as an alligatorid, specifically as a stem-caiman, as shown in the cladogram below.

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Concepts associés (5)

Diplocynodon

Diplocynodon est un genre éteint d'Alligatoroidea qui a vécu pendant le Paléocène et jusqu'au Miocène moyen en Europe. L'espèce type, Diplocynodon ratelii a été créée par le paléontologue français Auguste Pomel en 1847. Au , Diplocynodon steineri a été nommé du nom de la ville de Styrie en Autriche et Diplocynodon styriacus a été nommé en Autriche et en France. Une troisième espèce autrichienne, Enneodon ungeri, a été placée dans son propre genre.

Globidonta

Globidonta is a clade of alligatoroids that includes alligators, caimans, and closely related extinct forms. It is defined as a stem-based clade including Alligator mississippiensis (the American Alligator) and all forms more closely related to it than to Diplocynodon. The group's fossil range extends back into the Late Cretaceous with early alligatoroids such as Albertochampsa and Brachychampsa. Extinct globidontans were particularly common in North America and Eurasia, and their modern range also includes South America.

Ceratosuchus

Ceratosuchus ("horned crocodile") is an extinct genus of alligatorine crocodylian from latest Paleocene rocks of Colorado's Piceance Basin and earliest Eocene rocks of Wyoming's Bighorn Basin in North America, a slice of time known as the Clarkforkian North American Land Mammal Age. Like its modern relatives, Ceratosuchus was a swamp-dwelling predator. It is named for the pair of flattened, triangular bony plates that extend from the back of its head. The type species is C.