Researchers said Tiliqua frangens, or Frangens for short, lived about 50,000 years ago. Frangens. from Latin, means to break into pieces or smash, describing how strong the jaw was.

The lizard lived during the Pleistocene, alongside megafauna such as marsupial lions, diprotodons and short-faced kangaroos.

“Frangens was 1000 times bigger than the common Australian garden skinks (Lampropholis guichenoti, which weigh about 2g) and has a unique chunky, spiked profile,” says lead author Dr Kailah Thorn from the Western Australian Museum, who studied the fossils as part of her PhD at Flinders University.

“It reveals that even small creatures were supersized during the Pleistocene.”

Frangens is believed to be related to the living shingleback or sleepy lizard (Tiliqua rugosa), but is even larger and more heavily armoured, according to the new study published in Proceedings of the Royal Society of London B: Biological Sciences.

“These large, slow armoured lizards might have filled the ecological niche of small land tortoises, absent from modern Australia,” said co-author Professor Michael Lee from Flinders University and South Australian Museum.

Researchers said the extinction of Frangens coincided with the disappearance of megafauna and suggested end-Pleistocene extinctions were more extensive, affecting smaller creatures as well.

“Deciphering how Pleistocene animals adapted, migrated, or what eventually caused their extinctions might help us conserve today’s fauna, which faces pressures such as changing climate and habitat destruction,” Thorn said.

Diana Fusco, from the university’s palaeontology lab, says the mega skink’s existence was carefully pieced together from bones unearthed at Wellington Caves in NSW and fossils already held in museums around Australia.

“In the dig at Wellington Caves, we started finding these spiked armoured plates that had surprisingly never been recorded before,” she said.

“We knew we had something interesting and unique.”

Thorn said caves can be treasure troves when it comes to getting a handle on prehistoric biodiversity.

And that’s certainly been true of Cathedral cave in the Wellington system, where Frangens bones continue to be found.

“There used to be a natural hole in the ceiling … so there’s marsupial lions and thylacines and stuff in there as well that have fallen in, or wandered in, and not been able to get out again,” Thorn said.

“It’s a great way to sample biodiversity in a snapshot of time.”

A paper about the Frangens has been published in the Royal Society’s flagship biological research journal.