Mesosaurus

Mesosaurus is a very ancient and unusual reptile that lived in the first half of the Permian Period, 271-299 million years ago. What makes it unique is that it is the earliest known aquatic reptile.

Mesosaurus looks like a small gavial. It has an elongated body with a strong flat tail, and large hind legs. The fossil clearly shows that its front paws are pinned to its body, just as they were when moving in the water. The ribs are wide, strong, and securely cover the internal organs. The head is relatively small, and the mouth is studded with long needle-like teeth, which gives the Mesosaur a slightly comical appearance.

Mesosaurus spent most of the time in the water, hunting small fish, insect larvae and mollusks. However, it could move around on land confidently and there, on land, it laid its eggs, just as crocodiles do.

The skeleton is perfectly preserved: vertebrae, skull bones, phalanges and thin teeth are in excellent condition, though it is at least 40 million years older than the first dinosaurs!