TRANSCRIPT
A near perfect fossilised skeleton found in the South Australian desert has been the key to solving a 150-year-old megafauna mystery.
Giant kangaroos known as Protemnodon were first described in 1874 by British naturalist Sir Richard Owen, who differentiated them by their teeth, as was the custom of the time.
"The teeth turned out to be very variable, a lot more variable than Owen thought, and so basically for 150 years it's been really difficult to tell how many species there were and how to tell them apart."
That’s the voice of Palaeontologist Dr Isaac Kerr who is the lead researcher on the Flinders University study.
He’s examined hundreds of Protemnodon bones in museums across Australia, New Guinea, the UK and even the US, using a 3D scanner.
But it was an archaeological site at Lake Callabonna in arid South Australia where an important clue was unearthed.
The discovery of fossilised skeletons that had similar teeth. but very different bodies.
"The main tip off in the end was that proportions of the hind limb were very different between species and that's a strong indicator of kangaroos of a difference in locomotion and speed and efficiency of their hop. We talk about gearing, so slow or low gearing mid gearing and high gearing. So a red kangaroo has a very short femur, a very short upper leg and a very long shin bone. That helps the body to stay over the foot when they are hopping. Some did have that, others had about the same size femur and shin bone which similar to a tree kangaroo.”
The research which is published in the journal Megataxa led to the formal description of three Protemnodon species.
Protemnodon Viator lived in arid areas and was twice as big as a large red kangaroo.
Here’s what Isaac Kerr says about the viator.
“Very large, up to 170 kilograms with very long hind limbs. It was probably a fairly fast and efficient hopper. Not so quick and good as hopping as say a red kangaroo but similar in some respects and that was spread across Arid Australia. “
Another species - Protemnodon mamkurra was more robust, thick-limbed and slower moving, thought to have returned to forested areas on the southern coast from Western Australia to Tasmania.
Here’s Dr Kerr again.
"Some Protemnodon returned to densely forested habitat in places like new guinea, and Tasmania and the east coast of Australia and in that habitat it doesn’t pay to have such a quick efficient vient hop that you see in open habitat kangaroo, it’s much better to be slower moving and a bit more nimble to move through thick undergrowth so then you end up with kangaroos a bit more like a quokka or a potteroo."
Another species - Protemnodon dawsonae was described from fewer fossils and remains more of a mystery. It was most likely a mid-speed hopper. something like a swamp wallaby
The new discoveries will enable researchers to expand the knowledge of what these giants were getting up to.
"People can look at how they interacted with their environment, you know, did they move in mobs like living kangaroos do, did they box like living kangaroos."
Now researchers are heading to New Guinea where they hope to describe another giant kangaroo.
