Sphenosuchus
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Sphenosuchus Temporal range: Early Jurassic,195 Ma |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: |
Crocodylomorpha Haughton, 1924 |
| Genus: | †Sphenosuchus |
| Type species | |
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†Sphenosuchus acutus Haughton, 1915 |
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Sphenosuchus is an extinct genus of Crocodylomorpha from the Elliot Formation (Early Jurassic) of South Africa, discovered and described early in the 20th century. The skull is preserved very well but other than elements of the forelimb and isolated parts of the hind limb, the Sphenosuchus material is incomplete. It was probably quadrupedal, but may have been a facultative biped.
Sphenosuchus was first thoroughly described in 1972 by the British palaeontologist Alick Walker, in a paper in the journal Nature. Walker suggested, based on detailed (but still preliminary at that time) studies of the skull of Sphenosuchus and modern birds, that crocodylomorphs and birds might share an immediate common ancestor. Walker recanted his hypothesis in 1985, but restated and elaborated on it (in essence 'de-recanting') in a monograph published in 1990, which provided the most comprehensive description and discussion of Sphenosuchus yet published.
Broom believes with the evidence present in the specimens that Sphenosuchus is a Pseudosuchian which is well along the line that leads to the true Crocodiles. In a paper published by V Huene he emphasizes Sphenosuchus as a very important stage of crocodile evolution.
The type species, Sphenosuchus acutus is the only described species in this genus.
Out of the early Crocodylmorphs, Sphenosuchus was one of the largest. The skull was 192 mm in the length and the body an estimated total length of 1.4m. This genus is considered to have been carnivorous and cursorial. The found specimen consists of a nearly perfect but slightly crushed skull, a shoulder girdle, and a few limb bones so most of the known features come from the skull. The primary head of the quadrate meets the prootic and squamosal. The quadrate and pterygoid are not fused to the braincase and the basipterygoid articulation is free.The dentary is not gracile and has anterior swelling. The parietals are fused together. The post temporal fenestrae are known for the Sphenosuchus with the sizes being very variable among early Archosaurs but rather small in size for Sphenosuchus Has a scapula blade in a triangular shape. No clavicles present. Metatarsal I is reduced, II and IV are symmetrical and III is the longest. The nasals are long and narrow and pass from near the plane passing through the front of the orbits to the extreme anterior points of the snout. The frontals are large relatively and help to form a small part of the upper orbital margin and a large portion of the upper temporal fossa. The jugal is a large bone forming the whole of the lower orbital and almost all of the lower temporal bar. The parietal is a good sized element forming nearly the entire intertemporal region along with the majority of the occiput. There is no parietal foramen present. The dentary is slender and moderate in length, it appears to have roughly fourteen teeth with a third of them being larger than the others. Overall the skull is similar to those of crocodiles however it is slightly deeper.
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