Gamilaraay/Yuwaalaraay Elder Allan Tighe Snr was the first to notice unusually large bones appearing in the bed of the dry Barwon near Walgett, NSW, as the water receded.
Mr Tighe called on a friend, Associate Professor Dr Mark Moore, a University of New England (UNE) archaeologist and paleoanthropologist, to confirm his suspicion that the outsized remains belonged to no living creature.
Dr Moore, who has worked with the Gamilaraay/Yuwaalaraay community for many years, said the find is important to the Aboriginal community because it gives substance to Dreaming stories that allude to the past presence of great environment-shaping creatures.
"Some of these bones suggest they were sitting in still water close to the time that the animal died, so the area might have been a swamp or lake," he said.
"To date, we've analysed the bones simply exposed by the river. The next step is to thoroughly excavate four sites along the river where we might be able to find more bones in their original deposit. This will give us more contextual information and help us more precisely determine the age of the bones.
"But from the amount of bone we've seen already simply thrown up by the drought, it's a very promising discovery for the field of zoo archaeology and an exciting find for the local community."
Dr Moore rallied UNE paleontologist Michael Curry and zoo archaeologist James Roberts for a spontaneous trip to Walgett, where the bones were identified as remains of Australia's megafauna, the last of which died out about 50,000 years ago.
Several sites along the river have now yielded the bones of Megalania, a six-metre lizard; Phascolonus, a 300kg wombat; Protemnodon, a wallaby around twice the size of a modern grey kangaroo; and Diprotodon, a grazing, herbivorous relative of wombats and koalas that was around the size of a rhinoceros.
"It's not unusual for clusters of mega-fauna remains to be found in areas where there are artesian springs, but this is one of the first mega-fauna bone discoveries on the Murray-Darling river system," Dr Moore said.
UNE PhD student and mega-fauna expert Michael Curry said Mr Tighe's original find of the Megalania bones is particularly exciting.
"Finding isolated Megalania bones is uncommon, but finding multiple bones from the same individual, as we think this find, is rare," he says.
"Finding even a partial skeleton of Megalania would be a first, and a significant addition to our knowledge of the animal.
"This lizard was built similarly to a Komodo dragon, was around six metres in length, and weighed as much as a midsize car. With venom-secreting glands and serrated, knife-like teeth, it would have been one of the most formidable land predators to have lived in Australia since the dinosaurs."
"Megalania roamed the bush from about two million years ago, and became extinct sometime in the last 50,000 years; so the first people to arrive in Australia would almost certainly have encountered them.
"These lizards would easily have been able to kill and eat a human, and would have been dangerous and difficult to defend against.
"It's possible that these new finds will help us better understand the story of human arrival in Australia and the ecology of Australia before humans."
The scientists are in a race against time to excavate at least four megafauna riverbed fossil sites exposed by drought, before the rains return and the sites go underwater again for an indeterminate period.
The fossilised remains of mega-fauna, the giant relatives of the continent's modern animals, were identified by University of New England scientists who are now analysing the finds in search of a better understanding of Australia's human history and its pre-human prehistory.
UNE scientists are now planning further excavation at four sites on the Barwon. Haste is necessary - environmental releases of water from dams upstream may temporarily drown the sites, and the breaking of drought will again drown the sites for the foreseeable future.