Feather-tailed possums are tiny marsupials that belong to the family Acrobatidae. They have a distinctive tail that resembles a feather, which they use for balance and grip.
There are two living species of feather-tailed possums: the Australian feathertail glider (Acrobates pygmaeus) and the New Guinean feather-tailed possum (Distoechurus pennatus).
These two species are closely related, but they have different adaptations and lifestyles.
The Australian feathertail glider can glide from tree to tree using a membrane between its limbs, while the New Guinean feather-tailed possum lacks this ability and is more terrestrial.
Scientists have long wondered how these two species evolved and where they originated.
A recent study by palaeontologists from UNSW Sydney has shed some light on this mystery by analysing fossils of extinct feather-tailed possums from Riversleigh World Heritage Area in north-western Queensland.
The study revealed that the ancestors of both living species were present in Australia by at least 25 million years ago, and that the New Guinean feather-tailed possums migrated from Australia to New Guinea later in their evolutionary history.
These fossils represent the first 'deep-time' record of the whole family Acrobatidae, and provide insights into their diversity and evolution.
The fossils showed that the extinct species of Acrobates were similar to the living Australian feathertail glider, but had larger body sizes and more robust teeth.
They also had well-developed gliding membranes, indicating that they were adapted to living in forests that began to spread out in Australia during the Miocene epoch (23-5 million years ago).
According to the study, the extinct species of Distoechurus were similar to the living New Guinean feather-tailed possum, but had smaller body sizes and less robust teeth.
Moreover, they lacked gliding membranes, suggesting that they never developed gliding as an adaptation. Instead, they probably relied on their long tails and claws to move through the vegetation.
The researchers concluded that the extinct species of Acrobates and Distoechurus were closely related to each other, and that they shared a common ancestor in Australia before diverging into their living descendants.
They also suggested that the Distoechurus lineage migrated from Australia to New Guinea sometime after the Miocene epoch, when New Guinea emerged as a large landmass.
The study has important implications for understanding the evolution and biogeography of feather-tailed possums and other marsupials.
It shows that feather-tailed possums originated in Australia and diversified into different forms over time. It also shows that some of them colonised New Guinea and adapted to new environments.
The study also highlights the role of Riversleigh as a rich source of fossil information for Australian fauna.
Riversleigh has yielded fossils of many other marsupials, such as koalas, kangaroos, bandicoots and wombats, as well as birds, reptiles and mammals.
These fossils reveal how Australia's unique wildlife evolved over millions of years in response to changing climates and landscapes.
The study was published in Alcheringa: An Australasian Journal of Palaeontology, and was led by Prue Fabian, who conducted the research as part of her honours year at UNSW.
Fabian was supervised by Professor Mike Archer and Emeritus Professor Suzanne Hand from UNSW's School of Biological Earth and Environmental Sciences.
The study was supported by grants from the Australian Research Council and the National Geographic Society.
