Dicynodonts and Lystrosaurus

Dicynodonts were plant-eating therapsids with a toothless horny beak and a pair of tusks, from which their name 'two dog teeth' comes. They appear in the Middle Permian about 270 million years ago, and ranged in size from a rat to an elephant. They were the most diverse and abundant land herbivores of the Late Permian, and survived into the Late Triassic. Their fossils are common in the Karoo Basin of South Africa, where the Permian-Triassic boundary is recorded in layers of rock.¹

Lystrosaurus, a pig-sized dicynodont, survived the Great Dying and then spread over much of Gondwana in the early Triassic, making up most of the fossil animals in some layers. Its presence in Antarctica was confirmed in 1969 by Edwin Colbert, who found it at Coalsack Bluff, and its distribution became further evidence for continental drift. Dicynodonts were probably prey for gorgonopsians. Their dominance and collapse show how an extinction can leave a few hardy survivors to inherit the earth.¹²³