The bird, depicted in red ochre, stands awkwardly, its hammer of a head stretched far forward of its stocky body and massive thighs.
Adorning the side of a shallow rock shelter in the Arnhem Land plateau, it bears no resemblance to an emu, magpie goose, cassowary or any other living species. But it does look a lot like something else - a giant flightless bird, Genyornis newtoni, taller than a man and thought to have become extinct on the Australian continent about 45,000 years ago.
If the painting does indeed depict the long-gone thunder bird, it will join a handful of ancient artworks set to reignite an intense debate among experts about the history of Aboriginal occupation of Australia.
Either the painting is by far the oldest ever documented among the hundreds of thousands of indigenous art works scattered liberally over the continent. Or, in an equally intriguing scenario, Aboriginal man did not, as many argue, wipe out ancient megafauna very soon after arriving here 50,000 years ago, but co-existed with giant species (which included towering wombats, kangaroos and six-metre-long lizards) for perhaps tens of thousands of years.
The long-running debate among Australia's archaeologists, palaeontologists and anthropologists is set to flare again later this month when the ABC screens a ground-breaking four-part TV series, First Footsteps.
The series tracks the history of the Aboriginal occupation of Australia over the length and breadth of the continent, stretching back in time to when the mainland was still one with Tasmania, Kangaroo Island and Papua New Guinea.
Tracing the long sweep of human presence through artworks and artefacts, rare archival footage and interviews with experts and Aboriginal elders at field sites around the country, the series takes an unapologetic stand against the thesis that man was the chief agent of the megafauna's extinction.
Instead, it identifies the key culprit as the coming of the ice age about 30,000 years ago, an event that plunged as much as 90 per cent of the continent into drought.
Filmmaker Martin Butler, who produced the series with director Bentley Dean, says "We believe the ice age killed the megafauna, not the people. It could not have been the people, because in our view there is now good evidence that the giant species survived until about 30,000 to 25,000 years ago."
To support this stand, the series assembles evidence from several ancient artworks and preliminary findings from recent sites where massed remains of megafauna have been found.
Rock art expert Ben Gunn, who first identified the giant bird image as a likely depiction of Genyornis, is convinced whoever painted it saw the bird alive because the anatomy so closely matches what experts can recreate from the bones.
"There is the problem that we still don't know how long a painting can last out in the open," he concedes. (A date of about 28,000 years ago has recently been put on a charcoal-drawn rock fragment from a gallery of paintings at Narwala Gabarnmang, about 10 kilometres away.)
But Gunn says the palaeontologist he's been working with is happy it is a representation of Genyornis and "it's my inference that someone who could get that much detail would have to know the bird".
Another strong advocate for a later survival date for extinct megafauna is Professor Paul Tacon, of Griffith University, who's discovered what he's convinced is a depiction of a marsupial lion, further north in Arnhem Land.
The fierce carnivore was originally assumed to have died out 60,000 to 40,000 years ago but Tacon and colleague Steve Webb argue a contrary thesis in a paper submitted for publication in a leading international journal.
"What we think is going on is that megafauna were surviving in northern Australia until much more recently than they were in the south or the centre, and that the climate was better suited for their long-term survival in the north," Tacon said.
He and Webb have also found several "very old, naturalistic animal paintings that have key features of animals that have been extinct for a very long time ... in particular two paintings in different places of enormous kangaroos", with features typical of extinct macropods.
Collectively, he says, "these paintings suggest that those animals did survive until much more recent times and that they overlapped with humans for tens of thousands of years."
Tacon concedes his paper will "reignite debate in academic circles. Every time a paper related to it comes out, the debate fires up again."
The contrary theory, that humans wiped out the megafauna within a very short time of arriving here, is one that's been championed by some very big names in the Australian science world, including naturalist and climate change commissioner Professor Tim Flannery.
Flannery, who has not yet seen the series, concedes the marsupial lion may have lingered longer than the other megafauna. But he says the overwhelming weight of scientific evidence still points to a mass extinction event about 45,000 years ago, coinciding with human activity on the continent.
The series highlights some early findings from a site near BHP's South Walker Creek mine site in the Bowen Basin, in Queensland, where a rich deposit of megafauna bones and teeth have been found.
Chief investigator Dr Scott Hocknull, of the Queensland Museum, has had a preliminary dating for the sediments containing the bones of about 25,000 to 28,000 years ago. But he stresses dating of the bones themselves has yet to occur.
Regardless of where the scientific consensus eventually lands, the series makes a powerful case for better national appreciation of the sheer scale, longevity and richness of the cultural heritage of Aboriginal Australia.
Series consultant Peter Veth, a professor of rock art at the University of Western Australia, says: "I honestly don't think 90 per cent of the population has any idea of the scope and depth of the remains that are actually on the continent."
It was, he argues, a giant canvas for earlier Aboriginal populations, whose ancient song-lines and "Dreamtime superhighways" allowed cultural exchanges across thousands of kilometres.
"You go out into the middle of the Western Desert and you find some figures almost identical to those found at Burrup [on the north-west coast of Western Australia] ... and you think goodness, we have something extraordinary here. People were exchanging goods and ideas and art repertoires over vast distances."
The Burrup peninsula ( also known as Murujuga) lies 1600 kilometres north of Perth and possesses the largest concentration of petroglyphs - or engraved rock art - in the world.
So profusely did Aboriginal Australians chisel images into the hard rock surfaces that it's thought there are at least 1 million engravings spread over less than 400 square kilometres.
"Literally you will go for a 200-metre walk and see several thousand images," says local expert Dr Ken Mulvaney. "It's incredibly dense because people have been inscribing the landscape for upwards of 30,000 years."
This means that the progress of the ice age can be traced through the art record, with land animals giving way to depictions of the marine species once the ice melted and the seas rose.
But Burrup is also home to an increasing spread of heavy industry, with Woodside's Pluto gas plant there, a fertiliser plant and more recently an explosives plant commencing construction.
A long-standing campaign to get the federal government to nominate the area for World Heritage listing, strongly backed by academics, Aboriginal elders, lobby group Friends of Australian Rock Art, and the Greens, has so far failed to prod Canberra into action.
Former environment minister Tony Burke referred the issue to the Australian Heritage Council, which found the peninsula clearly met key criteria for World Heritage status.
But there the matter has stalled. Ironically, Aboriginal elders and Mulvaney met Burke late last month on the issue, just days before the return of Kevin Rudd as Prime Minister. Mark Butler has now taken over the federal environment portfolio, but his office gave no response to questions on the matter this week.
Western Australian Greens senator Scott Ludlum describes the plight of the remote Burrup as "just heartbreaking", adding, "from a political point of view, what has happened up there is absolutely unforgivable".
Nearly all the experts in the series agree the record of Australia's Aboriginal heritage needs much stronger and more co-ordinated government protection.
Michael Westerway, an archaeologist who has worked on Lake Mungo in western NSW - where evidence of modern humans dates back 42,000 years - hopes the series will inspire more Australians to value the riches that lie strewn across the continent. "We don't treasure our prehistory like they do in Europe," he says. "And that's a real tragedy."
First Footsteps screens on ABC from Sunday,