Scientists find evidence of tetrapods living in Antarctica during the early Triassic epoch, about 245 million years ago. The fossils were created when fine sand from an overflowing river poured into the animals’ burrows and hardened into casts of the open spaces. The largest preserved piece is about 14 inches long, 6 inches wide and 3 inches deep. The burrows’ relatively small size prompted scientists to speculate that their owners might have been small lizardlike reptiles called Procolophonids or an early mammal relative called Thrinaxodon.