Newly discovered non-hopping ancient kangaroo might be long-lost cousin of the modern roo
A team of scientists has discovered two new species of kangaroo believed to have roamed between 15 million and 23 million years ago that could be the ancestors to all modern kangaroos.
The two newly named species are the Balbaroo fangaroo and the Cookeroo hortusensis — the latter being what scientists believe to be the evolved relative to the former, fanged species.
Western Australian Museum mammal curator, Dr Kenny Travouillon, said it was an unidentified skull that had been stored at the Queensland Museum that sparked his interest as well as that of one of his PhD students.
The fossils were recovered from the Riversleigh World Heritage area in north-west Queensland sometime over the past 30 years, and languished in the museum until someone was able to identify them.
"There was no-one working on kangaroos for a few years, and so when I started looking at [these] kangaroos, I realised that this was a new species," Dr Travouillon said.
He gave the specimen to one of his PhD students who described the species and named it.
As she was finishing the project, she found herself sorting through a collection at the University of New South Wales, and it was here that she found the skull of the second unnamed species of extinct kangaroo.
"They would have looked quite similar to modern kangaroos, but slightly smaller, about the same size as a wallaby," Dr Travouillon said.
Unlike modern kangaroos, these ancient species did not yet hop.
"They would have walked on four legs instead of two," Dr Travouillon said.
To determine this, scientists looked closely at the leg bones of other specimens recovered from the area, and observed no evidence to suggest the bones would support an animal that hopped.
"Hopping actually occurred much later in the evolution," he said.
Limestone at Riversleigh makes it a fossil mecca
According to Dr Travouillon it was the geology that makes Riversleigh a valuable resource to scientists.
"It is the soil type and particularly the conditions at Riversleigh," he said.
"We have very few fossil sites in Australia that tell us about the evolution of marsupials, and Riversleigh is one of the rare ones."
Dr Travouillon said that although it made recovery difficult, it was because fossils at Riversleigh were encased in limestone that they were able to survive for millions of years.
"In most cases, if dirt covers the bones, it won't be preserved as well as it would in limestone," he said.
Farmers and explorers could help fill gaps in fossil records
Dr Travoullion said scientists were always on the hunt for the evidence needed to fill gaps in knowledge.
"The oldest fossil site in Australia that has marsupials is Murgon in Queensland," he said.
"That fossil site is around 55 million years old, then after that there's almost no fossil record until around 26 million years ago.
"Sites like Riversleigh, specifically, give us the end bit of the evolution of marsupials, but it doesn't actually tell us how they came to be in the first place."
He said everyday people exploring or working the less-travelled, remote corners of the country, might just discover something that helped narrow the gap in the fossil record.
"I think the fossil record does exist, it's just that we haven't found it yet," Dr Travouillon said.
"Australia is such a big continent and very few people are living on it.
"So it's really hard to find a new fossil site if you have no-one there actually looking for it.
"I think in the future we will probably find more sites of the right age that will tell us a bit more about the evolution of these animals."