A turtle shell that had been on display at Darwin's Museum and Art Gallery for years has been identified as a new prehistoric species of turtle. (Supplied: Gavin Dally/MAGNT)
In short:
Australian and US scientists discovered a new species of prehistoric snapping turtle after re-examining an unidentified fossil on display in a Northern Territory museum.
The new species, called Elseya mudburra, lived 13 to 14 million years ago in what is now the Tanami Desert.
What's next?
Scientists at the Museum and Art Gallery of the NT say the specimen could be one of hundreds of undiscovered species in the museum's collection.
Scientists have discovered a new species of prehistoric turtle from what was once a lush forest in Central Australia, after re-examining an unidentified fossil on display in the Northern Territory's largest museum.
For years, the fossilised turtle shell sat alongside stuffed birds, insects, lizards and marsupials at the Museum and Art Gallery of the Northern Territory (MAGNT).
Ever since senior curator and palaeontologist Adam Yates had started at the museum it had caught his eye, as he suspected it was unique.
"I'd had my eye on this particular fossil, but it was on display and I had many other jobs to be getting on with," he said.
Dr Adam Yates said he always had his suspicions the turtle might be a new species. (ABC News: Xavier Martin)
In early 2023, Dr Yates was encouraged to re-examine the specimen by an interested turtle expert from the US, herpetologist Mehdi Joseph-Ouni.
To do that, he had to spend months painstakingly extracting the fossil from its plaster display.
"I had lots of other projects on the go, so it's one that I would come back to every now and then when I had a spare moment," he said.
"I would go and work in the prep lab in removing a little bit more plaster."
The new species is a large carnivorous turtle named Elseya mudburra. (Supplied: Adam Yates/MAGNT)
When the process was finished, the pair were able to study an unusual protrusion on the underside of the fossil's shell.
That led to them discovering the specimen was a completely new species of snapping turtle — a large carnivorous turtle, long extinct, that they named Elseya mudburra.
"[The carapace] is made up of multiple bones that are joined together. Of particular interest is the first costal, which is actually a modified rib," Dr Yates said.
"The way the lower part of the shell joins to the first costal … is really significant and varies a lot in different turtles.
"In our one, it had a peculiar thick shape with an extra little process sticking down, that told us that it wasn't like anything that had been found before."
Dr Yates said Elseya mudburra was alive during the Miocene period of 13 to 14 million years ago and lived in rivers surrounded by lush forests in what is now the savannah country of the northern Tanami Desert.
The fossil was originally unearthed at a limestone deposit called Bullock Creek, near the remote community of Kalkarindji, which has previously yielded unique fossils of an ancient cassowary, a crocodile and possibly a giant snake.
Jared Archibald (left) and Adam Yates (right) inspecting split rock features at Bullock Creek, where the turtle fossil was found. (Supplied: Jared Archibald/MAGNT)
Bullock Creek's Elseya mudburra predates megafauna found at another Miocene-period fossil deposit in the Northern Territory, the Alcoota fossil beds, by about 5 million years.
Located much further south, bordering the Simpson Desert, the Alcoota fossil beds have yielded what has been labelled a "gold mine" of unique fossil specimens.
Possibility of more undiscovered species in museum collection
Below MAGNT's natural history exhibits are the museum's archives, where there are rows upon rows of labelled boxes and drawers housing taxidermied insects, birds, reptiles and marsupials.
Kirsti Abbot said MAGNT likely has millions of specimens in its collection. (ABC News)
According to MAGNT's head of science and ecologist Kirsti Abbott, the exact number of individual specimens in the collection is unknown, with hundreds of thousands of "lots" in the collection containing multiple specimens, similar to samples extracted from Bullock Creek.
"At MAGNT, we've got just over 830,000 lots. In terms of individual animals, that's millions, probably, when you're thinking about insects," Dr Abbott said.
Kirsti Abbott says it's likely there are more undiscovered species in MAGNT's collection. (ABC Radio)
"For those things that've been there for decades, or we haven't looked at, or we don't know much about that type of animal, there could be hundreds of undiscovered species in museums around the world, including ours."
With there being only a small number of experts for any given type of animal, Dr Abbott said that like the case of Elseya mudburra, discoveries of new species often occurred by chance within large collections.
"You might be casually looking through a drawer or showing somebody around and you notice something that you haven't noticed before," Dr Abbott said.
"[If] you travel down that investigative path, you might find a new species where you might not have looked before."