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.
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.
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.
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.
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.