Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic.

[2][3] The extreme shortness of the forelimbs relative to the hind limbs, the very small hands, and measurements of the vertebrae suggest that Postosuchus may have been committed to bipedal locomotion.

Along with remains of the skeleton, paleontologists also identify osteoderms, which were thick plates forming scales on its back, neck, and possibly above or under the tail.

[6] Postosuchus had a massively built skull, bearing dagger-like teeth, which was constructed narrow in front, and extended wide and deep behind.

[8] In 2013, a major study of the skeletal structure concluded that Postosuchus may have been an obligate biped based on evidence from the anatomy of the digits, vertebrae, and pelvis.

[10] In a 2022 article Postosuchus was considered predominantly bipedal, but probably still capable of supporting its weight on the forelimbs at low speeds, and an ontogenetic shift was noted, with the shortening of the arms as individuals aged, suggesting that at least hatchlings and juveniles were facultatively quadrupedal.

[4] In the following years further excavation in the Post Quarry, in Cooper Canyon Formation (Dockum Group), unearthed many remains of late Triassic terrestrial fauna.

The holotype of P. kirkpatricki (TTUP 9000), representing a well-preserved skull and a partial postcranial skeleton, was described along with other findings of this new genus by paleontologist Sankar Chatterjee in 1985.

[15] In 2008, Peyer et al., described a new species of Postosuchus, P. alisonae that was discovered by two UNC undergrad students, Brian Coffey and Marco Brewer in 1992 in Triangle Brick Co.

[17] P. alisonae represents the largest suchian reptile recovered from the quarry and the first articulated specimen of 'rauisuchian' archosaur found in eastern North America.

[18] Within the same period, paleontologist Charles Lewis Camp collected over a hundred "rauisuchian" bones, from what is now the Petrified Forest National Park of Arizona, which belong to at least seven individuals (UCMP A296, MNA 207C).

In 1943, Case again described a pelvis along with a pubis (UM 23127) from the Dockum Group of Texas, which dates from the Carnian through the early Norian stages of Late Triassic period.

[4] The first articulated skeleton referred to P. kirkpatricki (CM 73372) was recovered by David S. Berman of the Carnegie Museum of Natural History, in Coelophysis Quarry at Ghost Ranch, New Mexico, between 1988 and 1989.

Nesbitt (2011) also noted that CM 73372 differs from P. kirkpatricki and Rauisuchus in possessing a concave ventral margin of the ilium, and from P. alisonae in processing an asymmetrical distal end of the fourth metatarsal.

A phylogenetic analysis conducted by Nesbitt (2011), one of the most extensive on archosaurs, found CM 73372 to be the most basal crocodylomorph, thus referable neither to P. kirkpatricki nor to Rauisuchidae.

[29][4] The moist and warm region consisted of ferns, such as Cynepteris, Phelopteris and Clathropteris, gymnosperms, represented by Pelourdea, Araucarioxylon, Woodworthia, Otozamites and Dinophyton, and cycads like Sanmiguelia.

The fauna found in Dockum Group confirm that there were lakes and/or rivers containing fish such as the cartilaginous Xenacanthus, the lobe-finned Chinlea and the dipnoan Ceratodus.

On the margins of these rivers and in the uplands lived labyrinthodonts (Latiscopus) and reptiles such as Malerisaurus and Trilophosaurus, and even the archosaurs Coelophysis, Desmatosuchus, Typothorax, Leptosuchus, Nicrosaurus and Rutiodon.