Riojasuchus
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Live reconstruction of Riojasuchus
- Los Colorados Formation ( Argentina)
- Riojasuchus tenuisceps
Riojasuchus is an extinct genus of Ornithosuchidae from the group of archosaurs. Fossils of Riojasuchus were found in the Los Colorados Formation in Argentina and have been dated to the Late Triassic. The holotype, PVL 3827, consists of a complete skull and of a part of the Postkranialskeletts. He was described in 1967 by the Argentine paleontologist José Fernando Bonaparte first time scientifically.
Features
Riojasuchus reached a length of about 2 meters. Typical of this genre was a large premaxilla. The Antorbitalfenster is reduced by the cranial fossa. The lacrimal and postorbital were fused together. The Atlas, the second cervical vertebra was twice as big as the other cervical vertebrae. In the mandible, a small window was present. In contrast to other Ornithosuchiden Riojasuchus had relatively large spinous processes. The hind limbs of this animal were robustly built. The tibia had a diameter twice as large as the fibula. The metatarsals (metatarsals ) III. was longer than the first metatarsal IV.
System
Riojasuchus was a representative of Ornithosuchidae. Other members of this family were Ornithosuchus, the eponymous genus, and Venaticosuchus. The exterior classification of Ornithosuchidae is unclear. A study of Brusatte et al. (2010) came to the conclusion that the sister taxon of Ornithosuchidae Revueltosaurus is; both form the sister group of the Rauisuchia. According to Nesbitt (2011) the Ornithosuchidae is a basal ( primitive ) family of Pseudosuchia. This group within the Crurotarsi contains the Ornithosuchidae the extant crocodiles. The sister taxon of Ornithosuchidae eventually forming the group of Suchia.
Cladogram by Nesbitt (2011):
Riojasuchus
Ornithosuchus
Gracilisuchus
Turfanosuchus
Revueltosaurus
Aetosauria
Paracrocodylomorpha
Paleoecology
Riojasuchus was found in the Los Colorados Formation in Argentina. The deposits probably originate from the Upper Triassic. Other predators of this fauna are the 4 meter long Zupaysaurus from the group of Coelophysoidea ( dinosaurs). The Spitzenprädator among carnivores was probably Fasolasuchus, an animal of the Crurotarsi, which was the biggest predator of the Triassic with about 8 to 10 feet in length. Herbivores ( plant eaters ) were represented by the " prosauropods " Coloradisaurus, Lessemsaurus and Riojasaurus. Riojasuchus presented presumably for smaller synapsids as Dicynodonten.
Finds
The first discovery of Riojasuchus, the holotype PVL 3827, was described in 1967 by José Fernando Bonaparte scientifically. The remains consisted of a complete skull, a portion of the spine, one shoulder blade (scapula ), a coracoid, parts of Elle ( ulna ) and radius (radius ), a pubic bone ( pubis ), an iliac bone ( ilium ), part of the leg skeleton and a foot skeleton. Other discoveries were PVL 3828, consisting of an almost complete skull, a Tel spine, parts of the pelvic girdle, arm and leg skeleton and a heel bone, PVL 2826, which consists of almost all parts of the holotype, and PVL 3814, of which only eddy, a humerus and tibia are known.