Lystrosaurus, skull, a dicynodont Triceratops between 155 and 145 million

between 155 and 145 million years ago

In the 1990s

but hypotheses include the usual suspects (volcanism

Atlasaurus imelakai was a quadrupedal herbivorous sauropod

Lystrosaurus, skull, a dicynodont Triceratops between 155 and 145 millionLystrosaurus (meaning "shovel lizard", was a genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa. Four to six species are currently recognized, although from the 1930s to 1970s the number of species was thought to be much higher. Being a dicynodont, Lystrosaurus had only two teeth, a pair of tusk like canines, and is thought to have had a