Prestosuchidae
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 Prestosuchus
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Batrachotomus |
Prestosuchidae are a group of Triassic carnivorous archosaurs. They were large active terrestrial apex predators, ranging from around 2.5 to 6 or 7 meters in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling Erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gate. Prestosuchids flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanganyika), and Argentina. However experts agree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the Prestosuchidae constitute a distinct family apart from the Rauisuchidae.
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[edit] Classification
Alan Charig 1957 proposed a new family, the Prestosuchidae, to include genera like Mandasuchus, Prestosuchus, and Spondylosoma.
In 1967, Alfred Sherwood Romer placed Saurosuchus and Rauisuchus within the Erythrosuchidae and adopted the Prestosuchidae to include Prestosuchus, Procerosuchus, and Charig's "Mandasuchus"
The Prestosuchidae have often been included in the Rauisuchidae (e.g. Gauthier, 1986, Benton & Clark 1988, Benton & Walker 2002), although they have sometimes considered the sister group of the aetosaurs in a monophyletic Pseudosuchia (Juul, 1994), or as a small clade intermediate between basal Crurotarsi and more advanced archosaurs such as the Aetosauridae and Rauisuchidae (Gower 2002). J. Michael Parrish's 1993 cladistic analysis of crocodylotarsan archosaurs places the Prestosuchidae (including Prestosuchus, Ticinosuchus, and Saurosuchus) outside the crocodylomorph - poposaurid - rauisuchid - aetosaur clade. In most cladograms Prestosuchids are considered more advanced (or "derived" in cladistic terminology) than phytosaurs and ornithosuchids, but usually less derived than the poposaurids and aetosaurs.
Paul Sereno 2005 defines the Prestosuchidae as "the most inclusive clade containing Prestosuchus chiniquensis Huene 1942 but not Rauisuchus tiradentes Huene 1942, Aetosaurus ferratus Fraas 1877, Poposaurus gracilis Mehl 1915, Crocodylus niloticus (Laurenti 1768)."
[edit] Evolution of the group
The earliest known Prestosuchid is Mandasuchus from the Anisian of Tanganyika. This was already a large animal, about 4.75 meters long (Charig et al 1976). A similar but smaller form (perhaps the same genus) is Ticinosuchus of the Middle Triassic (Anisian-Ladinian) of Switzerland and Northern Italy, which was about 2.5 meters in length. The huge (6 meters long) Batrachotomus from the latest Middle Triassic (Late Ladinian) of Germany, and Prestosuchus of the early Late Triassic (Carnian) of South America may have been closely related animals. (Gower 2002). Yarasuchus was a lightly built animal from the Middle Triassic of India that also seems to belong to this group (Sen 2005). Finally, Saurosuchus was a huge carnivore, 6 or 7 meters long, whose fossils are known from the Late Carnian of Argentina.
[edit] References
- Benton, M. J. & Clark J.M. (1988), Archosaur phylogeny and the relationships of the Crocodilia in MJ Benton (ed.), The Phylogeny and Classification of the Tetrapods 1: 295-338. Oxford, The Systematics Assoc
- ----- & AD Walker (2002), Erpetosuchus, a crocodile-like basal archosaur from the Late Triassic of Elgin, Scotland, Zool. J. Linn. Soc. 136: 25-47.
- Charig, AJ 1957, New Triassic archosaurs from Tanganyika, including Mandasuchus and Teleocrater: Dissertation Abstracts. Cambridge University.
- ----- , Bernard Krebs, Hans D Sues, Frank Westphal 1976, Handbook of Paleoherpetology: Thecodontia, Verlag Dr. Friedrich Pfeil, Munchen
- Gauthier J.A. 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Sciences 8: 1-55.
- Gower, DJ (2002), Braincase evolution in suchian archosaurs (Reptilia: Diapsida): evidence from the rauisuchian Batrachotomus kupferzellensis, Zool. J. Linn. Soc. 136: 49-76
- Juul, L (1994), The phylogeny of basal archosaurs. Palaeontologia Africana 31: 1-38
- Parrish, JM (1993), Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13: 287-308
- Kasturi Sen, (2005) "A new rauisuchian archosaur from the Middle Triassic of India", Palaeontology, Volume 48 Issue 1, November 07, 2005
- Sereno, P. C. 2005. Stem Archosauria—TaxonSearch [version 1.0, 2005 November 7]
