Mesosaur

Mesosaurus Temporal range: Early Permian
Conservation status
Fossil
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Subclass:	Anapsida
Order:	Mesosauria
Family:	Mesosauridae
Genus:	Mesosaurus Gervais, 1865
Species
M. tenuidens (type) M. brasiliensis

Mesosaurus (which means "middle lizard") was a small marine reptile that lived during the late Carboniferous and early Permian period, roughly 320 to 280 million years ago. Fossils of the animal were found in Namibia, Africa [1] and parts of South America, such as Brazil, Uruguay, and Paraguay. [2] The widespread distribution of the fossil - particularly in those areas of Africa and South America which, when viewed on a map of the Earth, appear to 'interlock' - helped to reinforce the idea of continental drift. [3] [4]

The Mesosaurus resembles a small alligator, although the most common specimens are only 40 centimeters in length. Nonetheless, the largest specimen is almost 2 meters in length, and the Mesosaurus was probably the largest land animal of its time. It is believed to have fed on fish, or possibly crustaceans, by using its teeth as a sieve, rather like modern-day whales.

The Mesosaurus is the first known aquatic reptile, having returned to a watery way of life after evolving on land.