A 'delicately built' dinosaur that roamed Australia when it was part of Antarctica has been identified thanks to a volunteer's lucky find amid a 'jumble' of other fossilised bones.
Swinburne University palaeontologist Stephen Poropat led a research team that identified that a five-centimetre-long neck bone, or vertebra, that was found nearly five years ago belonged to a dinosaur known as an elaphrosaur.
The name means 'light-footed lizard' and the species has only been identified in a handful of places around the world after first being found in Tanzania in the early 20th century.
Elaphrosaur bones have never been found in Australia before.
The discovery by volunteer Jessica Parker in 2015 at Cape Otway, on the south-west Victorian coast, and its recent identification confirmed they lived here about 110 million years ago.
The identification of the fossil was published this month in Gondwana Research.
Cape Otway specimen found in ancient riverbed
Dr Poropat said the plant-eating dinosaurs belong to the group known as theropods, which have hollow bones.
"They are quite delicately-built animals who would have had long necks and a small head, and fairly short arms with four fingers," he said.
The vertebra indicated the animal it came from was about two metres in length, but other fossils found from the species shows they could reach up to six metres in length.
Specimens of elaphrosaur found in other parts of the world are much older, up to 160 million years old, but another elaphrosaur fossils found in Argentina around the same time as the Cape Otway specimen is the youngest.
Dr Poropat said the coastal spot where the fossil was found would have been the site of a fast-flowing river at the time, when Tasmania and Victoria were close, and Australia was much further south inside the Antarctic Circle.
There would have been long periods of darkness and diverse plant-life dotted the landscape.
"There were conifer trees, things like modern-day monkey puzzles. There were ferns and lots of flowering plants," he said.
"There were cycads, horse-tails, and ginkgo. Both of those latter groups are extinct in Australia today and yet they were thriving when the dinosaurs were around."
Due to the fact the specimen was located in rock that would have been a riverbed, it was mixed up with other fossils.
"Because a lot of these sediments are deposited by fast-flowing rivers we very seldom find a complete or partial skeleton because as they're transported a lot of the bodies disintegrate," he said.
"This was found in the same deposit was a jumbled-up series of bones belonging to meat-eating dinosaurs, small plant-eating ornithopod dinosaurs, lots of turtle bones, and bits of fish and teeth from other animals as well."
Area a fossil hotspot
Dr Poropat said the work of citizen scientists who volunteer their time to help on digs was crucial for learning more about dinosaurs.
"As this story tells, one bone can change our understanding completely," he said.
"If it belongs to a group of animals that we didn't know was represented in Victoria, let alone Australia before, it can shape our understanding of the fauna."
Cape Otway has been a hotspot for paleontologists since the 1980s with about a dozen different animals and five dinosaur species having been identified there, including a plant-eating dinosaur found in 2018 that was described as turkey-sized.
This elaphrosaur specimen was found at a site known as Eric the Red West, and other discoveries have been made at a nearby spot known as Dinosaur Cove.
