Orthosuchus

Extinct genus of reptiles from the early Jurassic of southern Africa

Orthosuchus (meaning "straight crocodile") is an extinct genus of crocodyliform that lived during the Early Jurassic, about 196 million years ago. It was first discovered in 1963 in the Red Beds Formation in the Qacha's Nek Province of Lesotho, southern Africa. The characteristics showed on its postcranial skeleton and the skull indicated that it is a crocodyliform. The finding is significant since some of the characteristics found on this specimen were believed to be absent until Jurassic. The external skull surface is covered randomly with small pits. The orbits are huge, with a complete dorsal roof made by the paired supraorbitals. The fossil resembles some features of a primitive crocodilian, one of them is the reduced antorbital fenestra. The classification of Protosuchidae is debatable, however, since Orthosuchus resemble some of the characteristics of Protosuchidae, it is believed to be in the part of this family. However, from appearance, archosaurs resemble more of crocodiles than of birds. Orthosuchus resembles a primitive form of crocodilian by some of its traits: the fusion midline together at the parietal, the form of the secondary palate, the fusion of pterygoid and quadrate, the extension of coracoid, radius, and ulna, and the form of tuber on the calcaneum.

The existing specimens of Orthosuchus were found in the Lower Jurassic Red Bed Formation in South Africa in 1963. The animal is probably quadrupedal because the fore limbs are approximately 91% the length of the hind limb, which also makes the walking on land easier. However, Orthosuchus may not be a good swimmer, since it has amphicoelous vertebrae, whereas modern crocodiles have procoelous vertebrae, which increase the mobility of the tail.