Austrosaurus mckillopi, one of Queensland's long-necked sauropods, has been rediscovered thanks to a team of Australian and British palaeontologists.
The Early Cretaceous period (104 million year old) dinosaur was first discovered in 1932 on Kunjen country, northwest of Richmond, Queensland - then it was lost.
(Image above: Bird's-eye view of the reconstructed Austrosaurus mckillopi site. The backbones (on the left side of the image) were excavated in the 1930s, and the ribs (projecting towards the top right) were dug up in 2014 and 2015.)
Attempts by palaeontologists to relocate the site during the 1970s and 1990s failed, and Swinburne palaeontologist Dr Stephen Poropat became intrigued by the mystery of the lost site when he studied the bones uncovered in 1932, currently in storage at the Queensland Museum.
"When I realised that the backbones at the museum probably formed a section of a dinosaur's spine, I hypothesised that more of the skeleton was waiting to be found," Dr Poropat says.
In 2014, he contacted Dr Tim Holland, former curator of Richmond's Kronosaurus Korner marine fossil museum, about relocating the site. Dr Holland enlisted the help of Richmond Mayor John Wharton – who grew up on Clutha station – to find the lost site and, hopefully, more of the skeleton.
Image: Dr Stephen Poropat
"When we failed to find the Austrosaurus site at ground level, John jumped into his helicopter," Dr Holland says. From the air they spotted two wooden posts – both of which had toppled over – that had once supported a sign marking the spot. Wharton then found fossilised portions of bone embedded in rock nearby.
"We were blown away," Dr Holland says
Three digs at the site between 2014-2015 uncovered six rib bones, which when placed with the vertebrae found in the early 1930s created a more complete picture of the dinosaur. Dr Poropat says the most exciting realisation was that portions of the ribs were embedded in the rock surrounding the left side of the backbones, which matched the ribs that we found in 2014-2015 - five of them from the left side too.
“"his means that the carcass of Austrosaurus came to rest on its left side, and it was not shifted much after it died allowing the bones to stay close to a life position," says Dr Poropat.
Because of its age, Austrosaurus might reveal something about the evolution of other sauropods in Australia. The sauropods commonly found in the Winton area, south of Richmond, lived five to ten million years after Austrosaurus. This means that Austrosaurus could potentially be their close relative, or even their direct ancestor.
"Unfortunately the bones are too incomplete and poorly preserved for us to be able to say much with certainty. Nevertheless, we can tell that Austrosaurus was at least distantly related to Winton's titanosaurs like Diamantinasaurus and Savannasaurus since it shares some features with them," Dr Poropat says.
Although the Austrosaurus site is now believed to be exhausted of fossils, the potential for future discoveries of important fossils in the Richmond area is huge.
"Rocks of the right age, deposited in a Cretaceous inland sea known as the Eromanga Sea, are close to the surface all over the Richmond region," says Dr Holland. "Who knows what else might be waiting to be found? A lucky discovery by a grazier, fossil hunter or tourist out there might be a game-changer."