Named By: Francois-Louis Paul Gervais - 1864-66.
Synonyms: Mesosaurus brasiliensis, Ditrochosaurus capensis, Mesosaurus capensis.
Classification: Chordata, Reptilia, Anapsida, Mesosauria, Mesosauridae.
Species: M. tenuidens.
Size: Approximately 1 meter long.
Known locations: South America, Southern Africa.
Time period: Early Permian.
Fossil representation: Known from complete skeletons.
is one of the first reptiles to return to an aquatic lifestyle. The
nostrils are on top of the skull and the legs are suited more for
aquatic movement than that on land. The tail may have sported a fin
similar to the earlier tetrapod amphibians, and the feet were webbed.
As an early reptile is possible that Mesosaurus
would have had to
return to the land to lay its eggs. When on land it might of had to
push itself with its legs as opposed to lift its body and actually
walk. A further development is the pachyostosis of the bones. This is
where the bones become thickened and more solid resulting in a denser
bone structure. This may helped to deal with buoyancy issues allowing
Mesosaurus to have greater agility in the water.
The teeth of Mesosaurus are very fine and were originally interpreted to have formed a comb like structure for filtering food out of the water. However, further specimens have cast doubt upon this method of feeding as the teeth are always too few to form such a structure. With this in mind it is more likely that Mesosaurus hunted small fish and invertebrates. It is generally considered that Mesosaurus dwelt in freshwater.
When the theory of continental drift was still being debated amongst the scientific community, the fossils of Mesosaurus recovered from both sides of the Atlantic ocean were taken as evidence to support the theory.