The Zarith is a Tyrannosaurus rex of Pellucidar. A young Zarith is roughly the size of a Shetland pony but presents a serious threat to animals at least as large as humans. These young animals are capable of delivering powerful blows with their fore paws which can knock a man senseless.

An adult Zarith is much bigger and hunts suitably large game such as the Tandor and the Thag.