The newly-discovered species, Lumakoala blackae, was comparable in size to the smallest-known members of the koala family (Phascolarctidae), with body-mass estimates of 2.2-2.6 kg. The discovery helps fill a 30 million gap in the evolution of Australia’s marsupials.
Reconstruction of early marsupials (left to right): the wallaby-sized herbivore Muramura williamsi, extinct koala relative Madakoala devisi and the calf-sized ilariid Ilaria lawsone. Image credit: Peter Schouten.
Lumakoala blackae lived in central Australia during the Oligocene epoch, about 25 million years ago.
“Lumakoala blackae weighed roughly 2.5 kg — about the size of a modern day brushtail possum, or a small domestic cat,” said Flinders University Ph.D. student Arthur Crichton.
“It probably ate mostly soft leaves, but wouldn’t have turned down an insect given the chance.”
“Our computer analysis of its evolutionary relationships indicates that Lumakoala blackae is a member of the koala family or a close relative, but it also resembles several much older fossil marsupials called Thylacotinga and Chulpasia from the 55 million-year-old Tingamarra site in northeastern Australia.”
“In the past, it was suggested the enigmatic Thylacotinga and Chulpasia may have been closely related to marsupials from South America,” he added.
“However, the discovery of Lumakoala blackae suggests that Thylacotinga and Chulpasia could actually be early relatives of Australian herbivorous marsupials such as koalas, wombats, kangaroos and possums.”
“This group (Diprotodontia) is extremely diverse today, but nothing is known about the first half of their evolution due to a long gap in the fossil record.”
“If our hypothesis is correct, it would extend the diprotodontian fossil record back by 30 million years.”
“We would really expect early diprotodontians to have been around at the time; molecular information suggests koalas, wombats, kangaroos and possums split off from other marsupials between about 65 million and 50 million years ago.”
The fossilized teeth of Lumakoala blackae were found at the site of Pwerte Marnte Marnte, south of Alice Springs.
“The discovery of Lumakoala blackae helps fill a major 30 million-year-old gap in Australian marsupial evolution,” said University of Salford paleontologist Robin Beck.
“These Tingamarran marsupials are less mysterious than we thought, and now appear to be ancient relatives of younger, more familiar groups like koalas.”
“It shows how finding new fossils like Lumakoala blackae, even if only a few teeth, can revolutionize our understanding of the history of life on Earth.”
“The study raises important new questions, including whether these relatives of Australian herbivorous marsupials once lived in South America and Antarctica.”
“There are South American fossils that look very similar to the Tingamarran marsupials.”
The authors also report the presence of two previously known species of koala — Madakoala and Nimiokoala — that lived alongside Lumakoala blackae, filling different niches in the central Australian forests that flourished 25 million years ago.
“Until now, there’s been no record of koalas ever being in the Northern Territory; now there are three different species from a single fossil site,” said Flinders University’s Professor Gavin Prideaux.
“While we have only one koala species today, we now know there were at least seven from the Late Oligocene — along with giant koala-like marsupials called ilariids.”
“These were the largest marsupials in Australia at the time, weighing in at up to 200 kg.”
“They lived alongside a strong-toothed wombat relative named Mukupirna fortidentata and a bizarre possum, Chunia pledgei.”
The findings were published in the September 4, 2023 issue of the journal Scientific Reports.
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A.I. Crichton et al. 2023. A probable koala from the Oligocene of central Australia provides insights into early diprotodontian evolution. Sci Rep 13, 14521; doi: 10.1038/s41598-023-41471-0
