A mini koala meandered through central Australia about 25 million years ago. The newly discovered species belonged to a community that contained the oldest known members of the koala family 鈥� and it could provide crucial missing information on the mysterious early evolution of marsupials.
The novel species 鈥� which has been named Lumakoala blackae 鈥� is represented by just by a dozen ancient teeth, mostly upper molars, found in fossil-bearing rocks near Alice Springs.
鈥淭eeth are good because they provide a huge amount of evolutionary and dietary information,鈥� says at Flinders University in Australia who led the analysis of the fossils. Since tooth shape doesn鈥檛 tend to vary a lot within species, differences between species can serve as 鈥渞oad maps for understanding the evolution of their relationships鈥�, he says.
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The teeth suggest that L. blackae weighed between 2.2 and 2.6 kilograms 鈥� tiny compared with the modern koala (Phascolarctos cinereus), which weighs between 4.1 and 13.5 kilograms. It probably munched away at relatively soft plant material, like young leaves and small fruits and maybe the occasional insect, rather than the tough eucalyptus leaves that today鈥檚 koala eat.
What鈥檚 more, L. blackae shared its environment with other koalas. Fossil teeth found in the same rocks belong to two previously known genera of prehistoric koalas, Madakoala and Nimiokoala. Also present in the community were perhaps two or three species of Ilariidae 鈥� a family of massive, koala-like marsupials weighing upwards of 200 kilograms that were the biggest land mammals in Australia at the time. 鈥淭hat鈥檚 really cool,鈥� says Crichton.
This suggests that, 25 million years ago, marsupials thrived in large, multi-species communities, says at The University of Queensland in Australia.
The discovery also helps throw new light on a 30-million-year gap in Australia鈥檚 fossil record. We know from fossils that some very primitive species of marsupials inhabited the landmass 55 million years ago, says Price. There is also evidence from fossils that most of the modern marsupial groups 鈥� such as kangaroos, possums, bandicoots and koalas 鈥� had appeared by 25 million years ago.
鈥淲hat the heck happened in between?鈥� says Price. 鈥淭here are a lot of mysteries about where Australian marsupials came from.鈥�
Although L. blackae comes at the end of that fossil gap and is 鈥渄efinitely something closely related to koalas鈥�, says Price, it also shares characteristics with other non-koala marsupials of today. This means it could represent a species closer to the primitive state from which Australia鈥檚 previously mega-diverse marsupial communities thrived 鈥� an idea that could be explored further with more fossil specimens.
鈥淒iversity across so many marsupial groups has dwindled dramatically,鈥� says Price. 鈥淭oday is the first time in the past 25 million years that there is only one koala species present.鈥�
Scientific Reports
