In an Australian first, palaeontologists have uncovered the head and body of a 100-million-year-old Plesiosaurs – a long-neck marine reptile – in the Queensland desert.

The fossil, which was uncovered near Mckinlay in Western Queensland, has been labelled the “the Rosetta stone of marine reptile palaeontology” by those involved after it was discovered by “The Rock Chicks” – a trio of fossil hunters led by an outback Queensland station owner.

Experts believe the new fossil may hold the key to unlocking the mystery around Australian plesiosaurs.

Queensland Museum dig site of a Plesiosaur near Mckinlay, QLD. Photo / news.com.au / Peter Wallis

The new skeleton and several other plesiosaurs and ichthyosaurs fossils discovered and collected on the field trip are now in the process of being taken to Townsville for preparation and further research.

Queensland Museum Network senior scientist and curator of palaeontology Dr Espen Knutsen described the magnitude of the find – stating it would become the first known head and body of an Australian elasmosaurus to be held in a museum collection.

“We were extremely excited when we saw this fossil – it is like the Rosetta stone of marine palaeontology as it may hold the key to unravelling the diversity and evolution of long-necked plesiosaurs (order) in Cretaceous Australia,” Knutsen said.

“We have never found a body and a head together, and this could hold the key to future research in this field.

 “Because these plesiosaurs were two-thirds neck, often the head would be separated from the body after death, which makes it very hard to find a fossil preserving both together, so we are using CT scanning to give us an insight into these magnificent animals.”

Experts stated the long-neck, “turtle-like” marine reptiles inhabited the dry, desert planes of Western Queensland between 145 and 65 million years ago when a “vast, shallow sea” covered the majority of the state.

In fact, Queensland hosts a bounty of fossil remains of the ocean’s inhabitants.

Queensland Museum Network CEO Dr Jim Thompson hoped the find would help Knutsen’s team better understand Queensland’s cretaceous marine reptiles.

“We now hold the only head and body of an Australian elasmosaur in the world, and this significant find will contribute greatly to vital research into Queensland’s Cretaceous past,” Thompson said.

“Queensland Museum Network holds one of Australia’s most complete plesiosaur specimens, nicknamed ‘Dave the Plesiosaur’, which was discovered in 1999. However despite having 80 per cent of its bones, it was missing a head, fins and tail tips.

“Through Project DIG, CAT scans and 3D models will help us interpret data and potentially describe a new species.”

Experts believe this is the first whole plesiosaur uncovered in Australia. Photo / news.com.au / Peter Wallis

As for Cassandra, Sally and Cynthia, aka The Rock Chicks, its just another feather in their caps – having uncovered a plesiosaur each, a kronosaurus, ichthyosaur and several fish and turtles over the years scouring the outback.

Cassandra said they were already preparing for their next ‘hunt “in 2023.

“Let’s keep the paleos busy,” she said.

“There are so many people who have helped get these amazing fossils to Queensland Museum, including our friends, Tom and Sharon, who helped us start digging two of the plesiosaurs,” Cassandra said.

There are more than a hundred species of plesiosaurs known across the world. Some had long necks and small heads, some had short necks with giant heads, and everything in between.

Elasmosaur plesiosaurs, which was recently uncovered, had long, narrow necks, broad flippers, small heads and streamlined torsos.

They mostly had thin, sharp teeth for catching fish – not for chewing or crushing.

Some plesiosaur remains have been discovered with stones preserved in the stomach area, suggesting they swallowed stones to either grind up food in their stomachs or as an aid in diving.

The work is supported by Project DIG, a A$7.6 million ($8 million) partnership between Queensland Museum Network, BHP and BMA.