Supersized marsupials roamed the Australian continent for millennia. But until now the understanding of giant kangaroos – or Protemnodon – has been confined to isolated bones and difficult-to-distinguish species.
Scientists have now identified three new species of the extinct giant kangaroo – Protemnodon viator, Protemnodon mamkurra and Protemnodon dawsonae, which lived from 5m to 40,000 years ago.
The Protemnodon viator, scientists say, weighed up to 170kg – double the weight of the heaviest present-day red males.
It was previously thought that most Protemnodon moved on all four legs but researchers now say this was only true of three or four species. Others moved like a quokka or potoroo, they believe, “bounding on four legs at times, and hopping on two legs at others”.
Isaac Kerr, the paper’s lead author, said the classification of the species would allow for future research on how the giant kangaroos evolved and responded to environmental change.
The Flinders University researchers took photographs and 3D scans of 900 specimens in 14 major museums in Australia, the UK, the US and Papua New Guinea.
They found significant variation between the species, such as different hopping methods – which Kerr, then a PhD student at Flinders University, described as “very unusual”.
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The differences could be associated with adaptations to the vastly different environments they lived in – from arid central Australia to the forested mountains of Tasmania and Papua New Guinea.
Kerr said while kangaroos might be Australia’s national animal, they are “just as New Guinean as they are Australian”.
“New Guinea today has groups of kangaroos we don’t even have … they’ve got three species of giant echidna that eat worms,” he said.
There is no clear explanation for why giant kangaroos went extinct while their close relatives, such as the grey kangaroo and wallaroo, did not, but Kerr suspects rapid environmental change spurred by human practices may have been a cause.
Gilbert Price, a palaeontologist who was not involved in the study, said the research strengthened Australia’s patchy fossil record.
“We don’t have massive fossil records [as seen overseas] … we’re not going to see frozen kangaroos or wombats,” he said.
“People often think we have a pretty weird modern ecosystem in Australia … but our animals are comparatively non-freaky compared to things we used to have in the past.”