MELBOURNE: Shirley is not any ordinary wombat.

The rare diprotodon fossil, believed to show the largest marsupial ever to have lived, was found on a cattle station in the Northwest Territories of Australia.

The cattle station land manager discovered the fossil last month and reported it to the Museum of Central Australia.

This colossal marsupial which strolled the Earth 2.5million years ago weighed three tonnes and was the size of an elephant and the Aussie team promptly named the remains 'Shirley'.

The skeleton is believed to be missing the skull, but includes the ribs, hips, spinal column and back legs.

Did they died out naturally or were hunted to extinction by early humans?

The bones may help solve this mystery behind the creature’s disappearance.

Territory Museum earth sciences curator Adam Yates said, “We are all sort of crossing our fingers and hoping that this may be the site that definitely shows human-megafaunal interaction, but I can't say that yet. There might be such things as cut marks or teeth marks underneath but we don't know that yet. It is all very exciting because a Diprotodon has not been found in the Northern Territory before. Any ice-age site from the tropical north of Australia is a rarity, there are very, very few such sites. I believe the coincidental arrival of humans at about that time or just before that time is significant.”