Tsoabichi

Tsoabichi is an extinct genus of caiman crocodylian. Fossils are known from the Green River Formation in Wyoming, and date back to the Wasatchian stage of the Eocene. The genus was named and described in 2010 by paleontologist Christopher A. Brochu, with the type species being Tsoabichi greenriverensis.[1] According to the current understanding of caiman evolutionary relationships, Tsoabichi is a basal member of Caimaninae and likely evolved after caimans dispersed into North America from northern and central South America, their main center of diversity in the Paleozoic.

Description
Some living caimans such as the Spectacled Caiman have a "spectacle", or a bony ridge between the eyes. Tsoabichi lacks a spectacle, but it does have three smaller ridges between the orbits, or eye sockets. In Tsoabichi, distinct rims are seen around the supratemporal fenestrae, two holes on the skull table. Much of the supraoccipital bone is also found on the skull table, and forms a V-shape. To either side of the V-shaped supraoccipitals are the parietal bones, which form the posterior margin of the skull table. Along the snout, the nasal bone forms a thin ridge, and narrows as it approaches the external naris where the nostrils are located.[1]

The dorsal osteoderms (bony scutes along the back) are wider than those of other caimans. Some have two keels on their outer surface. Tsoabichi also has bipartite ventral osteoderms on its underside.

Phylogeny
Tsoabichi was included in a phylogenetic analysis when it was described in 2010. Brochu (2010) found it to be a basal member of Caimaninae closely related to the living genus Paleosuchus.[1] The analysis of Hastings et al. (2013), which included several more species of caimans, also placed Tsoabichi in a basal position within Caimaninae as the sister taxon to crown group caimans (the smallest clade that includes all living caimans and their most recent common ancestor). Eocaiman and Culebrasuchus were successively more basal than Tsoabichi.