A chance discovery has unearthed an unusual toothless dinosaur that roamed Australia around 110 million years ago – a time when it was still attached to Antarctica.
Discovered by a volunteer on Victoria’s Cape Otway, the bone belongs to a two-legged elaphrosaur. Meaning “light footed lizard”, elaphrosaurs have been found in Tanzania and a handful of other places around the world. This makes the Victorian elaphrosaur a curious discovery – not only is it the first discovery in Australia, but it lived around 40 million years later than most other known elaphrosaurs.
The findings have been published in the journal Gondwana Research.
Chance discovery by volunteer
The story began in early 2015, when volunteer Jessica Parker unearthed a strange five-centimetre bone during an annual Dinosaur Dreaming dig at Cape Otway, south-west of Melbourne. Parker discovered the bone at a Cretaceous-aged fossil site known as Eric the Red West.
It was originally identified at Melbourne Museum as a vertebra from the flying reptile pterosaur.
A 3D rendering of the elaphrosaur vertebra. Credit: Ruairidh Duncan/Museums Victoria.
But when Adele Pentland and Stephen Poropat from Swinburne University of Technology attempted to work out exactly what type of pterosaur, it didn’t quite make sense.
“Pterosaur neck vertebrae are very distinctive”, says Pentland.
“In all known pterosaurs, the body of the vertebra has a socket at the head end, and a ball or condyle at the body end. This vertebra had sockets at both ends, so it could not have been from a pterosaur.”
Pentland last year led the research team that discovered a new species of pterosaur, Ferrodraco lentoni, in central Queensland.
“We soon realised that the neck bone we were studying was from a theropod: a meat-eating dinosaur, related to Tyrannosaurus rex, Velociraptor, and modern birds,” says Poropat.
“The only catch – this ‘meat-eating dinosaur’ probably didn’t eat meat!”
A curious dinosaur in a curious location
Elaphrosaurs were odd looking dinosaurs. Running fast close to the ground on two legs, they had a slender body, stubby arms, and a long neck and delicate toothless skull.
Its two main known relatives –Elaphrosaurus bambergi from Tanzania and Limusaurus inextricabilis from China – lived near the end of the Jurassic Period, 160-145 million years ago. Another elaphrosaur fossil found in Argentina dates to around the same period as the Cape Otway specimen, but is slightly younger.
At just two metres the Australian elaphrosaur was rather small compared to its relatives. It also lived in quite a different climate – 110 million years ago Australia was much further south inside the Antarctic circle.
They are thought to have started life eating a wide variety of food, but as they aged lost their teeth and transitioned to a plant-based diet.
“The few known skulls of elaphrosaurs show that the youngsters had teeth, but that the adults lost their teeth and replaced them with a horny beak,” says Poropat.
“We don’t know if this is true for the Victorian elaphrosaur yet, but we might find out if we ever discover a skull.”
The discovery has researchers rethinking where, and when, elaphrosaurs may have lived. While only few fossils have ever been found, the Australian discovery opens up the possibility they were more widespread than thought. And with the Australian and Argentinian fossils dating much younger than their relatives, they may have lived over a wider period.
The dinosaur graveyard at the Eric the Red West site awaits further exploration. The discovery site was likely a fast-flowing river at the time, meaning it is a rich jumble of bones from different species. However, that adds a complication, in that it is rare to find a complete or even partial skeleton.
“New discoveries like this elaphrosaur fossil overturn past ideas, and help to interpret discoveries yet to come” says Museums Victoria’s Tim Ziegler, who assisted the researchers.
This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.
