Fossil Evidence for Continental Drift
Mesosaurus
Fossils of Mesosaurus, a freshwater, crocodile-like reptile that lived during the early Triassic time
period (between 250 and 200 million years ago), are found only in Southern Africa and Eastern South
America. Mesosaurus was an early aquatic relative of reptiles, and lived in freshwater lakes and
ponds. Long and slim, it measured about 1 meter (3.3 feet) long. It had webbed feet for swimming and
a long tail that may have supported a fin. The skull and tail were both long and narrow, and
the animal probably moved in a wave-like motion through the water, propelled by its feet and tail, as it
fed on small crustaceans and other prey with its jaws, which were full of long, thin, pointed teeth.
Mesosaurus had nostrils on top of its head, allowing it to breath at the surface of the water, similar to a
crocodile. Mesosaurus may have rarely, if ever, ventured onto land. It would have been
physiologically impossible for Mesosaurus to swim across the long, salty ocean between the continents
of South America and Africa. This suggests that South America and Africa were once joined together.
Cynognathus
Cynognathus is an extinct mammal-like reptile that lived on
land. The name literally means ‘dog jaw’, as it had large canine
teeth for chewing meat. Cynognathus was as large as a
modern wolf and lived during the Triassic time period (250 to
240 million years ago). It is found as fossils only in South Africa
and South America, suggesting the continents were once
connected. Cynognathus was a heavily built animal, and
measured around 1 meter long. It had a particularly large head,
with wide jaws and sharp teeth. Its tail was short, and its legs
were tucked under its body, allowing it to move quickly. It possibly had hair on its body. It would not
have been able to swim long distances such as
across an ocean.
Lystrosaurus
Lystrosaurus, which literally means ‘shovel reptile’, was dominant on land in the early Triassic time
period, 250 million years ago. It is thought to have been an herbivore and grew to approximately one
meter in length, with a stocky, barrel- shaped body like a pig. Fossils of Lystrosaurus are only found in
Antarctica, India, South Africa, and Madagascar. It had only two teeth, a pair of tusk-like canines, and
is thought to have had a horny beak that was used for biting off pieces of vegetation. The front legs
were more powerful than the back legs, and it was thought to be a powerful digger that nested in
burrows. It would not have been able to swim across a vast ocean.
Glossopteris
Glossopteris was a woody, seed-bearing shrub or tree, named after the Greek descripton of ‘tongue’ –
a description of the shape of the leaves. Some reached 30 meters tall. It evolved during the Early
Permian (299 million years ago) and went on to become the dominant species throughout the period,
not becoming extinct until the Triassic time period. Fossils are found in Australia, South Africa, South
America, India, and Antarctica. Glossopteris seeds were too large and heavy to be carried by animals
or wind across oceans.