Reptiles of the Late Triassic

crocodile-like phytosaurs

Phytosaurs were common reptiles during the Late Triassic.


Archosaurian reptiles were the predominant faunal element in the Late Triassic of Northern Arizona representing the majority of terrestrial carnivores and herbivores. The archosaurs or "ruling reptiles," consist of the dinosaurs, crocodiles, birds, and Triassic crocodile-like forms such as aetosaurs, phytosaurs, rauisuchians, and crocodylomorphs. Except for modern birds and crocodiles, all of these forms are now extinct. However, because of recent findings of dinosaurs with feathers in China and other similarities between the two groups, many paleontologists now consider birds a modern form of dinosaur.

Phytosaurs are the most common fossil vertebrate found at Petrified Forest National Park. These animals were very crocodilian in nature and probably lived a very similar lifestyle frequenting the streams and rivers of the Late Triassic. They most likely fed on fish and smaller reptiles.

Aetosaurs were large, quadrupedal, heavily armored crocodile-like reptiles. They had a short head with blunt peg-like teeth suggesting an herbivorous diet although it is possible they may have also fed on insects. Aetosaurs commonly found in the park include Typothorax and Stagonolepis.

The dominant terrestrial predators during the Late Triassic were the rauisuchians including the terrifying Postosuchus. This massively built animal was several meters in length with a heavy head full of sharp serrated teeth, similar but unrelated to the later tyrannosaurid dinosaurs.

The crocodylomorphs are distant ancestors of today's crocodiles. Interestingly these were very small, gracile carnivores that were completely terrestrial in nature. The most common crocodylomorph found in the park is the "sphenosuchian" Hesperosuchus.

Petrified Forest National Park Triassic Reptiles Taxa List
(Revised January 12, 2006)

Acaenosuchus geoffreyi (Stagonolepididae)
Acallosuchus rectori (Archosauriformes incertae sedis)
Desmatosuchus spurensis (Stagonolepididae)
Desmatosuchus smalli (Stagonolepididae)
Rioarribasuchus chamaensis (Stagonolepididae)
Hesperosuchus agilis (Sphenosuchidae)
Leptosuchus adamanensis (Phytosauridae)
Leptosuchus crosbiensis (Phytosauridae)
Smilosuchus gregorii (Phytosauridae)
Paratypothorax sp. (Stagonolepididae)
"Parrishia mccreai" (Sphenosuchidae)
Poposaurus gracilis (Poposauridae)
Postosuchus sp.(Rauisuchidae)
Pseudopalatus buceros (Phytosauridae)
Pseudopalatus jablonskiae (Phytosauridae)
Pseudopalatus macauleyi (Phytosauridae)
Pseudopalatus pristinus (Phytosauridae)
Revueltosaurus callenderi (Pseudosuchia incertae sedis)
Shuvosaurus sp. (Shuvosauridae)
Calyptosuchus wellesi (Stagonolepididae)
Trilophosaurus dornorum (Archosauromorpha)
Typothorax coccinarum (Stagonolepididae)
Vancleavea campi (Archosauriformes)
cf. Eucoelophysis sp.

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