A groundbreaking scientific discovery has been found on a remote outback property, once home to an ancient inland sea.

The 7.1m-long fossil of an ichthyosaur, a large marine predator that lived in an inland sea in Western Queensland more than 100 million years ago, is believed to be the most complete fossil of its kind ever found in Australia.

It was discovered at Toolebuc Station in Mckinlay, just over 400km northwest of Longreach, in 2023 by enthusiastic fossicker Cassandra Prince, who said the monumental find began with just one small rock.

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“We were emu bobbing one day, which is just walking around looking for fossils, and I found this piece of rock with a bit of bone in it, so I was very confident that the rest of the body was down under the dirt,” Prince said.

“I dug straight down, that’s called the sweet spot, when we hit a little bit of rock. And then we worked around which way the rock is going.”

After waiting a year to dig the site properly, Prince said the ancient marine reptile only took about five hours to uncover.

“And then we had this beautiful specimen,” she said.

Prince had sought permission to dig the site from property owner Sam Daniels, who has since donated the find to the Australian Age of Dinosaurs museum in Winton.

Museum founder David Elliott said the discovery has turned into one of the most complete ichthyosaur fossils ever found in Australia.

“In fact, it looks like it is the most complete,” he said.

“Until we prepare it, we won’t really know what we’ve got (and) just how complete it is. But to have this much of it — it goes all the way down to the tail — to have this much of a marine reptile from this area is extremely rare.

“A lot have been found but nothing complete. So, this is great news.”

The fossils will be transported to the museum, where the finer and more tedious work of reconstruction and rock removal will begin.

“We’ll number every individual piece ... and that and that’s how we’ll take it back to the museum,” Elliott said.

The fossils are covered in layers of rock, which will be carefully removed by pneumatic scribes, a type of tool that uses compressed air to chip away rock particles while leaving the more delicate fossil intact.

“It’s going to take thousands of hours but this specimen is worth every minute of it,” Elliott said.

“You’re looking at something that was swimming around an inland sea that covered western Queensland around 100 million years ago, and it’s almost perfect condition — it is an amazing specimen.”