Animal Fossils The Mesosaurus is an extinct reptile similar to a lizard. Scientists think this animal lived around 265 million years ago. Fossil evidence tells us that the Mesosaurus was approximately 3 feet long. The Mesosaurus’ fingers and toes were webbed, so they looked more like paddles than hands and feet. These powerful paddles were useful for chasing fish and other aquatic animals. One unique feature of this reptile is that it lived on land but returned to freshwater (lakes and rivers) to hunt its prey. The Mesosaurus was an ancestor to present-day amphibians. Since the Mesosaurus would breathe through nostrils on the top of its skull, scientists think it fed on prey similar to the way a crocodile feeds.
During the 1800s, scientists discovered fossils of the Mesosaurus in only two regions, South America and parts of southern Africa. This is interesting to scientists because these two regions are separated by the voluminous Atlantic Ocean. How do you think the Mesosaurus fossils could have ended up in these two places? Scientists who study these fossils know that they could not have swum across the vast ocean!
Paleontologists (scientists who study fossils) have also found evidence of another animal that lived 250 million years ago. This animal is known as the Lystrosaurus. The Lystrosaurus was a large lizard about the size of a pig. It lived on land and, similar to the Mesosaurus, has only been found in certain places on Earth. According to paleontologists, these reptiles lived in Africa, India, and Antarctica. Can you imagine a reptile living in cold and icy Antarctica?

What conclusions can you draw from this single piece of information about animal fossils?