Proterochampsidae

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Proterochampsidae
Temporal range: Middle - Late Triassic, 237–216Ma
Proterochampsa BW.jpg
Life restoration of Proterochampsa
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Proterochampsia
Family: Proterochampsidae
Romer, 1966
Genera

Proterochampsidae is a family of archosauriforms. Proterochampsids may have filled an ecological niche similar to modern crocodiles, and had a general crocodile-like appearance. They lived in what is now South America in the Middle and Late Triassic.

Description[edit]

Proterochampsids have long, crocodile-like skulls. The posterior portion of the skull is wide while the snout is very narrow. Most proterochampsids also have downturned snouts. Like many early archosauriforms, they also have dermal armour.

Proterochampsids have small holes called dorsal fenestrae at the top of their skulls. Unlike other early archosauromorphs, they do not have parietal foramina, which in many reptiles holds a parietal eye. The postorbital bones behind the eye sockets have thick, jagged crests. As another diagnostic feature of the group, the holes that allow the passage of the internal carotid artery through the braincase open at the sides of a bony projection called the basipterygoid process. Proterochampsids are primitive in that they have simple plate-like pelvises, but they lack small bones in the vertebra called intercentra that are common in earlier reptiles.

As in most archosaurs, distinguishing features can be seen in the shape of the ankle bones. A projection on the calcaneum bone called the calcaneal tuber is narrow and positioned downward relative to other lateral projections on the bone. The calcaneum also has a facet that attaches to both the fibula bone of the leg and another tarsal, or ankle bone. A hemicylindrical facet on the calcaneum attaches to another bone in the ankle called the astragalus. The astragalus has facets that attach to the tibia and fibula that are adjacent to each other.

Classification[edit]

Proterochampsidae was named in 1966 by A.S. Romer in his book Vertebrate Paleontology, 3rd edition. Members such as Proterochampsa and Cerritosaurus had been known for several decades prior to the family's creation. Proterochampsids were originally thought to be close relatives of crocodilians based on their similar appearance. In the following years, proterochampsids were frequently associated with Proterosuchia, another group of long-snouted Triassic archosauriforms. As phylogenetic studies became more common in the 1980s and 1990s, proterochapsids were found to be a distinct group closely related to true archosaurs. Recent studies have placed Proterochampsidae as either the sister taxon of Archosauria (the closest relatives of archosaurs), or the sister taxon of Archosauria and Euparkeria.[1] Recently, the unusual Late Triassic archosauriform Doswellia has been placed as the closest relative of proterochampsids. Because doswelliids are more closely related to proterochampsids than to any other archosauriform, the two groups form their own clade.[2]

Seven species have been assigned to Proterochampsidae: Cerritosaurus binsfeldi, Chanaresuchus bonapartei, Gualosuchus reigi, Rhadinosuchus gracilis, Tropidosuchus romeri, Proterochampsa barrionuevoi, and Proterochampsa nodosa. P. nodosa was assigned to its own genus Barberenachampsa in 2000, but it is generally still considered to be a species of Proterochampsa.[3] Proterochampsids have occasionally been placed in a larger group called Proterochampsia. Under this classification, Cerritosaurus, Proterochampsa, and Tropidosuchus are basal forms, while Chanaresuchus, Gualosuchus, and Rhadinosuchus form the family Rhadinosuchidae.[4]

Genera[edit]

Genus Authority Age Location Unit Notes Images

Cerritosaurus

Price (1946) Ladinian

 Argentina

Santa Maria Formation

Assigned to Proterochampsidae by Carroll (1988)

Chanaresuchus

Romer (1971) Ladinian

 Argentina

Chañares Formation

Chanaresuchus.jpg

Gualosuchus

Romer (1971) Ladinian

 Argentina

Chañares Formation

Proterochampsa

Reig (1959) Norian

 Argentina

Ischigualasto Formation

Rhadinosuchus

Huene (1942)

Ladinian

 Brazil

Santa Maria Formation

Tropidosuchus

Arcucci (1990)

Ladinian

 Argentina

Chañares Formation

References[edit]

  • A. S. Romer. 1966. Vertebrate Paleontology, 3rd edition. University of Chicago Press, Chicago 1-468 [M. Uhen/M. Uhen/M. Carrano]
  1. ^ Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". Bulletin of the American Museum of Natural History 352: 1–292. doi:10.1206/352.1. 
  2. ^ Julia B. Desojo, Martin D. Ezcurra and Cesar L. Schultz (2011). "An unusual new archosauriform from the Middle–Late Triassic of southern Brazil and the monophyly of Doswelliidae". Zoological Journal of the Linnean Society 161 (4): 839–871. doi:10.1111/j.1096-3642.2010.00655.x. 
  3. ^ Langer, M.C.; Ribeiro, A.M.; Schultz, C.L.; Ferigolo, J. (2007). "The continental tetrapod-bearing Triassic of South Brazil". In Lucas, S.G.; and Spielmann, J.A (eds.). The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41. pp. 201–218. 
  4. ^ Kischlat, E.; Schultz, C.L. (1999). "Phylogenetic analysis of Proterochampsia (Thecodontia: Archosauriformes)". Ameghiniana 36 (4): 13R. 

External links[edit]