A tooth discovered in ancient fossil grounds in northwest Queensland belongs to a metre-long platypus-zilla, scientists say.
The tooth was found at Riversleigh World Heritage Area, 265km northwest of Mount Isa, by a group of UNSW researchers who say it's the first evidence of the giant platypus Obdurodon tharalkooschild.
The tooth is yet to be dated but is likely to be between five million and 15 million years old.
The modern platypus is toothless as an adult and is unlikely to be the immediate descendant of the giant specimen.
Professor Mike Archer told AAP that means it's possible that multiple kinds of platypuses once coexisted.
But researchers know very little about what these giant platypus offshoots looked like.
"These things could have had wings and we wouldn't know it," Prof Archer told AAP.
"While we know a lot now about the teeth ... and we know a little bit of the skull... we do not know anything about the body," he said.
The researchers believe the platypus could have been strong enough to bite through turtle shells.
Riversleigh World Heritage Area has been described as one of the most important fossil sites in the world.
The previous discovery of an entire skull there was the first evidence that toothed platypuses lived in Australia.
The study has been published in the Journal of Vertebrate Palaeontology.
