Giant 20-foot-long raptor dinosaurs once roamed Australia, according to a new study that could rewrite the evolutionary history and hierarchy of predators on the continent.
The research, published in the Journal of Vertebrate Paleontology on Thursday, identifies five new species of four-legged dinosaurs whose fossils were unearthed from Victoria’s coastline.
Researchers excavated dinosaur shin bones and vertebrae at two fossil sites in Victoria – the upper Strzelecki Group dated to 121 million years ago and the Eumeralla Formation from about 113 million years ago.
The fossils provide unique insights into an ancient Australian ecosystem dominated by powerful “megaraptor” dinosaurs measuring 6-7 metres in length.
Two of the new megaraptor species are the oldest known globally and shed light on the evolutionary history of the group that includes the iconic velociraptor made famous by Jurassic Park films.
The latest study highlights the role played by Australia’s dinosaurs in the ecosystems of the ancient world, a large part of which was clustered into the giant supercontinent Gondwanaland. These “megaraptorids” lived alongside the smaller “carcharodontosaurs”, which were 2-4 metres long, as well as the even smaller but more agile “unenlagiines” or “southern raptors”.
“Two megaraptorid specimens from the upper Strzelecki Group demonstrate that this clade had achieved large body size at the time of its first appearance in the fossil record,” scientists said.
Jake Kotevski, a co-author of the study, called the latest discovery “groundbreaking” due to the unique insights it offers into Australia’s ecosystem during the Cretaceous era between 145 and 65 million years ago.
“It’s fascinating to see how Victoria’s predator hierarchy diverged from South America, where carcharodontosaurs reached Tyrannosaurus rex-like sizes up to 13 metres, towering over megaraptorids,” Mr Kotevski said.
“Here, the roles were reversed, highlighting the uniqueness of Australia’s Cretaceous ecosystem.”
The new study offers “compelling evidence” for the interchange of animals between Australia and South America via Antarctica during the Early Cretaceous era, scientists said.
It also highlights the key contributions of community volunteers working alongside seasoned researchers to further understanding of Australia's dinosaurs.
“The findings also challenge previous assumptions about body-size hierarchies in Gondwanan predator ecosystems highlighting Victoria’s unique Cretaceous fauna,” said Thomas Rich, senior curator of vertebrate palaeontology at Museums Victoria Research Institute.
