Paleontologists have identified four new fossil feathertail possum species (family Acrobatidae) from the fossilized specimens found in the Late Oligocene to Middle Miocene deposits of the Riversleigh World Heritage Areain northwestern Queensland, Australia. The four new species — two of them belong to the modern genus Acrobates and two to the modern genus Distoechurus — are the first pre-Pleistocene fossil representatives of the Acrobatidae family to be described.
Feather-tailed possums (Distoechurus pennatus).
The Acrobatidae is a highly distinctive family of small tree-dwelling marsupials.
The family comprises of only three living species: Acrobates pygmaeus and Acrobates frontalis of Australia, and Distoechurus pennatus of New Guinea.
Acrobates species inhabit coastal sclerophyll forests and tall woodlands in eastern Australia.
Distoechurus pennatus occurs throughout New Guinea from sea level to 1,900 m, where it is widespread in rainforests, as well as in regenerating rainforests.
These marsupials have distinctive elongate hairs that project down the length of the tail, leading to the common names of feathertail gliders for the gliding Acrobates species, and feathertail possum for the non-gliding Distoechurus pennatus.
They are omnivorous, feeding on a mixture of nectar, fruits and invertebrates.
“An analysis of extinct species found at Riversleigh World Heritage Area fossil deposits in north-western Queensland revealed that ancestors of both groups of possums were present in Australia by at least 25 million years ago,” said University of New South Wales Professor Mike Archer.
“As Riversleigh started revealing its prehistoric treasures, we discovered four different species of feathertail possums, the first ‘deep-time’ fossil record known for the whole family.”
The team’s analysis indicates that the new fossil species postdate the divergence of the Acrobates and Distoechurus lineages from each other.
As such, they provide a test of existing molecular estimates for the timing of the Acrobates–Distoechurus split.
“Not much was known about these species in the fossil record and how they related to their modern-day descendants,” said University of New South Wales Dr. Prue Fabian.
“Not only did we find two new species related to the Australian feathertail gliders, the species of Acrobates, but more surprisingly, two new species related to the New Guinean Distoechurus pennatus.”
“This confirms that Distoechurus possums didn’t originate in New Guinea as was once thought, they actually originated in Australia before moving north to New Guinea.”
“Millions of years ago, these ancestral feather-tails lived in a very different continent than the one we know today,” said University of New South Wales Professor Suzanne Hand.
“For one thing, New Guinea was largely underwater. At most, New Guinea consisted then of a collection of small, low-lying islands.”
“New Guinea has only risen to the heights it is now over the last 12 million years. And sometime after that mountain-building began, animals from Australia were able to colonize that emerging northern portion of the Australian continent which became New Guinea.”
“Climate change and a gradual drying of mainland Australia from about 15 million years ago is said to be the factor that led to some Australian possums evolving gliding as an adaptation to the changing environment,” Professor Archer said.
“When Australia started to dry out from about 15 million years ago, the forests began to open up.”
“Gradually replacing the inland rainforests were sclerophyll forests that were more open.”
“As this occurred, there was an incentive to find safer ways to get from one tree to another without coming down to the ground where something was waiting to gobble you up.”
“This was probably the trigger that led to some groups becoming gliders.”
“Younger feather-tails in drying Australia became gliders while the feather-tails in New Guinea did not.”
The discovery is reported in a paper in the Alcheringa, an Australasian Journal of Palaeontology.
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Prudence R. Fabian et al. First known extinct feathertail possums (Acrobatidae, Marsupialia): palaeobiodiversity, phylogenetics, palaeoecology and palaeogeography. Alcheringa: An Australasian Journal of Palaeontology, published online August 27, 2023; doi: 10.1080/03115518.2023.2242439
