Mesosaurus Fossil Site

Mesosaurus tenuidens

The Mesosaurus is probably one of the most convincing examples to prove the drifting of continents. The same genus in the same rock formations is to be found in both southern Africa and South America. In southern Africa the fossils can be found in the Whitehill formations, while in South America they are to be found in the Irats formations.

Both these formations were located in shallow sees, in basins and river mouths where the bottom layers were without oxygen and contained hydrogen sulphide. This caused the bottom to be toxic and without bottom dwelling creatures. It is also held that due to this the dead Mesosaurus did not decay as it sank to the bottom and in this way was perfectly preserved.

In southern Africa the Whitehill formation forms part of the Ekka group. These formations are between 280 and 320 million years old. In southern Africa these formations stretch over 300 000 square kilometers. They are the Karas-Karoo basin in southern Namibia, the Kalahari-Karoo basin of which our fossil trail is part and then there is the Haub basin in northern Namibia where even in the Doros crater Mesosaurus have been found.

The Whitehill see was shallow, between 30 m and 150 m. There was no influx of sediments by river and most were blown in by the wind. The seas were largely flat with huge swamps and were calm with few waves. The bottom layers were salty with fresh upper parts. Except for the Mesosaurus there were also two fish genera, two types of crab and prawn and also insect wings were found. Plant leaves has also been discovered.

Mesosaurus had long bent teeth with jagged shapes like the early amphibian. The teeth were embedded in the jaws and were fixed in a hinge like fashion so that they could bend outwards from the jaw when it closed. Mesosaurus had 31 vertebreae just before the tail.

Mesosaurus possibly hibernated but not in mud since there feet are not designed to borrow. They possibly laid there eggs on the beaches like modern day turtles. Due to the shape of the front feet the Mesosaurus moved with great difficulty on land , but were profound swimmers by using their tails and possibly webbed feet to propel them in the water. Even small Mesosaurus of 35 cm were found far from land. The biggest were about 2m long making them the largest animals of their time. The Mesosaurus is believed to have been filter feeders due to the structure of the teeth and fed on plankton, fish eggs and small larva. The Mesosaurus is related to early reptiles –the Cotulosauria from which all reptiles evolved.