1. An extinct small aquatic reptile from the Permian period, known from fossils found in South America and Africa, used as evidence for continental drift.
Usage: paleontology; scientific term

Examples

• The mesosaur was a freshwater reptile that lived approximately 300 million years ago.
• Fossils of mesosaurs have been discovered in both Brazil and South Africa, supporting the theory of Pangaea.
• Scientists use mesosaur remains as key evidence that South America and Africa were once connected.
• The mesosaur was relatively small, measuring only about 3 feet in length.
• Paleontologists study mesosaur teeth and skeletal structures to understand Permian ecosystems.