Saurosuchus
| Saurosuchus | ||||||||||||
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Skeletal reconstruction of Saurosuchus galilei |
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| Temporal occurrence | ||||||||||||
| Upper Triassic (late Carnian ) | ||||||||||||
| 230 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Saurosuchus | ||||||||||||
| Reig , 1959 | ||||||||||||
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Saurosuchus ("lizard crocodile"; sauros = "lizard, lizard"; Suchos = " Sobek ") is an extinct genus of archosaurs from the relationship of crocodiles. It is traditionally attributed to the Rauisuchia , although many researchers currently consider this group to be invalid (because it is paraphyletic ). With a length of 7 m,this carnivore was significantly larger than its close relatives, only the less well-known Fasolasuchus could have been larger.
Saurosuchus lived in what is now Argentina during the Upper Triassic and is known for several partial skeletons from the Ischigualasto Formation , an important fossil deposit . The holotype specimen consists of a complete but deformed skull, vertebrae, osteoderms, and part of the pelvis . The hind legs, tail, neck and shoulder blade are known of other skeletons . Some teeth and skull fragments from the Chinle Formation in Arizona have also been attributed to Saurosuchus ; However, later studies showed that these bones do not belong to Saurosuchus , but to another, related genus. Saurosuchus was first scientifically described by Osvaldo Reig in 1959 . The only species is Saurosuchus galilei .
description
Saurosuchus is one of the largest rauisuchia . Since a complete skeleton is not known, its size is estimated to be around 6 to 9 m. Like related genera, Saurosuchus ran quadruped (four-legged). He had a deep skull that was wide in the brain skull area and narrow in front of the eyes. The teeth are large, bent back, and jagged. The roof of the skull and the upper jaw show depressions, a feature that is not found in other Rauisuchians. The front bones (fronatle), which are located at the top of the skull, are enlarged and formed thick bulges above the eyes. The cervical vertebrae are shortened and robust and form a strong neck. On the back sat skin bone plates (so-called osteoderms ), which were arranged in two rows on each side of the body. The individual osteoderms were leaf-shaped and strung together closely.
Systematics
Saurosuchus was probably closely related to the genera Batrachotomus and Prestosuchus . The systematic position of these three genres is, however, controversial. For example, Stephen Brusatte and colleagues (2010) summarize Saurosuchus , Batrachotomus and Prestosuchus as Prestosuchidae . These form the sister taxon of the Rauisuchidae , which include Rauisuchus and Postosuchus among others . Both groups belong to the Rauisuchia .
However, Nesbitt (2011) considers the Rauisuchia and Prestosuchidae to be paraphyletic : According to him, they do not include all descendants of their common ancestor. He comes to the conclusion that Saurosuchus , Batrachotomus and Prestosuchus split off independently of each other from the main line of development that leads to the crocodiles. He ascribes these genera to the Loricata , a group to which the crocodiles and some other original crocodile-like representatives are counted. The following cladogram shows the Rauisuchia system according to Nesbitt (2011):
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Paleoecology
The fossils come from the 230 million year old layers of the Ischigualasto Formation in Argentina. He was probably one of the top predators in his area. Other carnivores of the Ischigualasto Formation include the smaller Venaticosuchus , an Ornithosuchidae , the Chiniquodontidae (a group of therapsids ), as well as some of the earliest dinosaurs , such as the 1 m long Eoraptor and the larger, approximately 3 m long Herrerasaurus . Typical herbivores of this ecosystem were Hyperodapedon , a Rhynchosauria ; some aetosaurs ; Ischigualastia , a Dicynodontia from the Kannemeyeridae ; some Traversodontidae such as Exaeretodon , a group of Therapsida , and herbivorous dinosaurs such as Pisanosaurus .
Individual evidence
- ↑ a b c d Sterling J. Nesbitt: The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades (= Bulletin of the American Museum of Natural History. No. 352). American Museum of Natural History, New York NY 2011, doi : 10.1206 / 352.1 , digital version (PDF; 32.69 MB) .
- ↑ a b María J. Trotteyn, Julia B. Desojo, Oscar A. Alcober: Nuevo material postcraneano de saurosuchus Galilean (Archosauria: crurotarsi) del Triásico Superior del centro-oeste de Argentina. In: Ameghiniana. Vol. 48, No. 1, 2011, ISSN 0002-7014 , pp. 13-27.
- ↑ a b c Oscar Alcober: Redescription of the skull of Saurosuchus galilei (Archosauria: Rauisuchidae). In: Journal of Vertebrate Paleontology. Vol. 20, No. 2, 2000, pp. 302-316, doi : 10.1671 / 0272-4634 (2000) 020 [0302: ROTSOS] 2.0.CO; 2 .
- ^ Andrew B. Heckert, Spencer G. Lucas, Stan E. Krzyanowski: The rauisuchian archosaur Saurosuchus from the Upper Triassic Chinle Group, Southwestern USA, and its biochronological significance. In: Andrew B. Heckert, Spencer G. Lucas (Eds.): Upper Triassic Stratigraphy and Paleontology (= New Mexico Museum of Natural History & Science. Bulletin. 21, ISSN 1524-4156 ). New Mexico Museum of Natural History and Science, Albuquerque NM 2002, pp. 241–247, digitized version (PDF; 1.33 MB) .
- ↑ Randall B. Irmis: The vertebrate fauna of the Upper Triassic Chinle Formation in northern Arizona. In: Sterling J. Nesbitt, William G. Parker, Randall B. Irmis: Guidebook to the Triassic formations of the Colorado Plateau in Northern Arizona. Geology, paleontology, and history (= Mesa Southwest Museum. Bulletin. No. 9, ISSN 1558-5212 ). Mesa Southwest Museum - Southwest Paleontological Society, Mesa AZ 2005, pp. 63-88, online (PDF; 1.82 MB) .
- ^ A b William D. Sill: The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts. In: Bulletin of the Museum of Comparative Zoology. Vol. 146, No. 7, 1974, ISSN 0027-4100 , pp. 317-362, digitized version (PDF; 24.37 MB) ( Memento of the original from August 12, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ↑ Stephen L. Brusatte, Michael J. Benton , Julia B. Desojo, Max C. Langer: The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida). In: Journal of Systematic Palaeontology. Vol. 8, No. 1, 2010, pp. 3-47, doi : 10.1080 / 14772010903537732 .
- ↑ Hans-Dieter Sues : Staurikosaurus and Herrerasauridae. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06726-6 , pp. 143-147.
- Jump up ↑ Raymond R. Rogers, Carl C. Swisher III, Paul C. Sereno , Alfredo M. Monetta, Catherine A. Forster, Ricardo N. Martínez: The Ischigualasto Tetrapod Assemblage (Late Triassic, Argentina) and 40 Ar / 39 Ar Dating of Dinosaur origins. In: Science . Vol. 260, No. 5109, 1993, pp. 794-797, doi : 10.1126 / science.260.5109.794 , PMID 17746113 .
- ^ José F. Bonaparte : Annotated list of the South American Triassic tetrapods. In: Second Gondwana Symposium. South Africa, July to August 1970. Proceedings and Papers. Council for Scientific and Industrial Research, Pretoria 1970, pp. 665-682.
Web links
- Saurosuchus galilei on DigiMorph