A TEAM of palaeontologists and volunteers will work like forensic scientists for the next month while excavating and studying a "50,000-year-old crime scene".

The team led by Queensland Museum palaeontologist Scott Hocknull will head the team of eight people excavating a riverbed at South Walker Creek mine site for bones of tropical megafauna that roamed northern Australia between 30,000 and 1.5million years ago.

The targets are two apex predators.

MIGHTY BITEY: A tooth from an extinct giant freshwater crocodile exposed at St Lawrence in 2016. Contributed

The search was sparked after previous expeditions to the site 40km west of Nebo revealed something unusual about the megafauna; they had puncture marks.

Mr Hocknull said looking at the initial images he was sent in 2008, he couldn't believe what he was seeing.

"When I found out they were fossil bones I was quite excited," he said. "A lot of images we are sent claiming to be fossils are actually rocks."

The location also had the experienced palaeontologist perplexed.

"The other thing that I was scratching my head about was that it was found in an area we would not expect to find bones. Traditionally you wouldn't go looking in that sort of place for fossils."

FANG FIND: Excavating a jawbone from an extinct giant marsupial Diprotodon at South Walker Creek. Contributed

Mr Hocknull's eureka moment came when he discovered that many of the fossils had puncture marks and there were large teeth recovered from the site.

"I asked myself 'why on earth are these bones being preserved where they were?' and then I realised that this was an ancient dinner plate for a massive freshwater crocodile about 7m long," he said.

These megafauna remains, including part of the world's largest known marsupial Diprotodon, were thrown around and busted into fragments making it a very difficult site to excavate.

The team visit the internationally significant site for tropical megafauna for four weeks each year, and each time they discover something completely new. This year they are looking more remains of the 7m crocodile, along with an Australian lion Thylacoleo after its bones were discovered at the site.

"It's not like a lion of Africa. It's a marsupial so it has a pouch," Mr Hocknull said. "It's Australia's apex predator."

He said it dominated in the southern states while in the north it was more the reptilian predators.

"The two didn't get along," he said.