Fossils of extinct late Paleozoic plant and animal species are found on widely separated continents. These fossils are found in environments where the plants and animals would not have been able to live.
Glossopteris was a type of seed fern that left fossils on South America, Africa, Madagascar, Indian subcontinent, Antarctica and Australia. Glossopteris seeds were too heavy to travel across the oceans.
Lystrosaurus and Cynognathus were both land reptiles that lived; neither could swim across the oceans. Mesosaurus was swimming reptile but was unable to live in salt water and could not have swum across the oceans.
Wegener thought that the only reasonable explanation for the the distribution of these fossils was that the continents were joined at the time the plant and animal species lived.