Diprotodon and Australia's giant marsupials

Diprotodon optatum, the largest marsupial that ever lived, stood about 1.8 metres at the shoulder, grew up to about 3 metres long and weighed perhaps 2.7 tonnes, a plant eater related to wombats and koalas. It was named by Richard Owen in 1838 from bones sent from Wellington Caves in New South Wales. In the 1890s the remains of many individuals were dug from the clay of Lake Callabonna in South Australia, where animals had become trapped in mud.

Australia separated from Antarctica around 35 million years ago and was an island continent, so its marsupials evolved in isolation. The Pleistocene megafauna of Australia included Diprotodon, the giant short-faced kangaroo Procoptodon, the marsupial lion Thylacoleo, the large flightless bird Genyornis and a giant monitor lizard, Varanus priscus. Diprotodon lived across much of the continent, and bone beds such as Callabonna hint that it sometimes lived in groups. The species disappeared with most of the other giants around the time humans spread across Australia.