might be related to the giant anteater. Since Shaw first described the species, its name has undergone four revisions: from M. aculeata to Ornithorhynchus hystrix, Echidna hystrix, Echidna aculeata and finally, Tachyglossus aculeatus. The name Tachyglossus means "quick tongue", in reference to the speed with which the echidna uses its tongue to catch ants and termites, and aculeatus means "spiny" or "equipped with spines". The short-beaked echidna is the only member of its genus, sharing the family Tachyglossidae with the extant species of the genus Zaglossus that occur in New Guinea. Zaglossus species, which include the western long-beaked, Sir David's long-beaked and eastern long-beaked echidnas, are all significantly larger than T. aculeatus, and their diets consist mostly of worms and grubs rather than ants and termites. Species of the Tachyglossidae are egg-laying mammals; together with the related family Ornithorhynchidae, they are the only extant monotremes in the world. The five subspecies of the short-beaked echidna are each found in different geographical locations. The subspecies also differ from one another in their hairiness, spine length and width, and the size of the grooming claws on their hind feet. T. a. acanthion is found in Northern Territory and Western Australia. T. a. aculeatus is found in Queensland, New South Wales, South Australia and Victoria. T. a. lawesii is found in coastal regions and the highlands of New Guinea, and possibly in the rainforests of Northeast Queensland. T. a. multiaculeatus is found on Kangaroo Island. T. a. setosus is found on Tasmania and some islands in Bass Strait. The earliest fossils of the short-beaked echidna date back around 15 million years ago to the Miocene epoch, and the oldest specimens were found in caves in South Australia, often with fossils of the long-beaked echidna from the same period. The ancient short-beaked echidnas are considered to be identical to their contemporary descendants except the ancestors are around 10% smaller. This "post-Pleistocene dwarfing" affects many Australian mammals. Part of the last radiation of monotreme mammals, echidnas are believed to have evolutionally diverged from the platypus around 66 million years ago, between the Cretaceous and Tertiary periods. However, the echidna's pre-Pleistocene heritage has not been traced yet, and the lack of teeth on the fossils found thus far have made it impossible to use dental evidence. The short-beaked echidna was commonly called the spiny anteater in older books, though this term has fallen out of fashion