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Diapsida : Archosauromorpha

Beaked, lizard-like reptiles

Trilophosaurus skeleton
Skeleton of Trilophosaurus.
The trilophosaurs are a group of beaked herbivores from the Triassic of North America and Europe. The best-known form is Trilophosaurus from the Upper Triassic of Arizona, New Mexico, and Texas. Other trilophosaurs include Tricuspisaurus and Variodens from the Upper Triassic of Europe. Teraterpeton from the Upper Triassic of Nova Scotia has a longer, lower skull than Trilophosaurus, but it is similar in having chisel-like cheek teeth and a toothless beak, and it is probably a close relative. Anisodontosaurus, known only from a fragmentary jaw from the Middle Triassic of Arizona, has sometimes been suggested to be an early trilophosaur; however, it is too incomplete for any certainty.

The skull of Trilophosaurus is short, wide, and tall, with bumpy, chisel-like cheek teeth and a toothless beak at the front of the jaws. The tall, wide skull had room for large jaw muscles, and Trilophosaurus probably ate rough or woody plant material. The rest of the body was wide, low to the ground, and lizard-like. Trilophosaurus was moderate sized — about a meter long without the tail, and up to 2.5 meters long overall. Although trilophosaurs do not seem to have been very diverse, they were abundant in some places in North America. Rhynchosaurs were not common in the Upper Triassic of North America so trilophosaurs may have filled the niche that was occupied by rhynchosaurs in other parts of the world.


  • Benton, M.J. 2005. Vertebrate Palaeontology, 3rd Ed. Blackwell Publishing, Malden, MA. 455 pp.
  • Carroll, R.L. 1988. Vertebrate Paleontology and Evolution. W.H. Freeman and Company, New York. 698 pp.
  • Heckert, A.B., S.G. Lucas, L.F. Rinehart, J.A. Spielmann, A.P. Hunt, and R. Kahle. 2006. Revision of the archosauromorph reptile Trilophosaurus, with a description of the first skull of Trilophosaurus jacobsi, from the Upper Triassic Chinle Group, West Texas, USA. Palaeontology 49(3):621-640.

Text by Matt Wedel, 5/2007; Trilophosaurus photo by Ghedoghedo (CC BY-SA 3.0)