Supersized marsupials roamed Australia and PNG forests for thousands of years; however, until now, understanding giant kangaroos—known as Protemnodon—has been an almost impossible task.
Now, scientists from Flinders University have used 3D modelling, photographs, and more than 800 different specimens from museums in Australia, PNG, the UK, and the US to identify three new species—Protemnodon viator, Protemnodon mamkurra, and Prontemnodon dawsonae—that lived between 5 million and 40,000 years ago.
The research published yesterday, Systematics and palaeobiology of kangaroos of the late Cenozoic genus Protemnodon (Marsupialia, Macropodidae), found “highly unusual” variations between species, including bone structure and hopping methods. The differences between species attributed to the vastly different environmental conditions—from arid central Australia to the forested mountains in Tasmania and PNG.
Until now, scientists believed that Protemnodon moved on all four legs, with the research now saying this was only true of three or four species – others moved like a quokka or potoroo, “bounding on four legs at times, and hopping on two legs at others.”
Isaac Kerr, the study’s lead author, said the species’ classification would assist future research into how giant kangaroos evolved and responded to environmental change.
He also noted that whilst Kangaroos are now considered Australia’s national emblem, “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,” Dr Kerr said, adding that whilst there is no clear explanation why giant kangaroos went extinct whilst grey kangaroos and wallaroo thrived, rapid environmental change spurred by human practices may have been a cause.
The research follows the discovery of multiple complete fossil kangaroo skeletons from Lake Callabonna in arid South Australia in 2013, 2018 and 2019. These fossils allowed researcher Dr Isaac Kerr, then a PhD student, to unpick a nearly 150-year-long puzzle around the identities of the species of Protemnodon – discovering two other species, Protemnodon mamkurra and Protemnodon dawsonae, in the process.
“We photographed and 3D-scanned over 800 specimens collected from all over Australia and New Guinea, taking measurements, comparing, and describing them. It was quite the undertaking,” Dr Kerr said, adding, “It feels so good to finally have it out in the world after five years of research, 261 pages, and more than 100,000 words.”
“Living kangaroos are already such remarkable animals, so it’s amazing to think what these peculiar giant kangaroos could have been getting up to.”
By about 40,000 years ago, all Protemnodon were extinct on mainland Australia, with researchers reporting that the species survived a little longer in dense PNG and Tasmanian forests. This extinction occurred despite their size, adaptations, habitat and geographic range differences.
“It’s great to have some clarity on the identities of the species of Protemnodon,” says Flinders Professor Gavin Prideaux, a co-author of the new article in Megataxa.
“The fossils of this genus are widespread and are found regularly, but you often have no way of being certain which species you’re looking at. This study may help researchers feel more confident when working with Protemnodon.”