Australian Research Expedition Finds Native Lizard Ancestor

Some animals widely associated with the Australian continent - wombats, platypuses, kangaroos, and even the extinct thylacine (marsupial tiger) - were found to have fossil ancestors located in central parts of South Australia.

A new expedition, this time to a large inland salt lake, has uncovered a tiny new skink - a fossil ancestry to the modern Australian blue-tongued lizards. Found in the earth deposits of the Namba Formation, the new discovery will be named in honor of renowned Flinders University professor and lizard researcher Mike Bull who passed away in 2016.

Oldest Skink To Date

With their findings detailed in a Royal Society's Open Science report, researchers have designated the discovered fossil Proegernia mikebulli. The skink has been dated at 25 million years old, making it the oldest discovery on the continent. It was discovered by an expedition team from Flinders University, together with volunteers and paleontologists from the South Australian Museum, at a fossil site in Lake Pinpa - situated on a 602,000 square hectare area known as the Frome Downe Station.

By tracing the crusted shoreline of the saltwater Pinpa, researchers soon came across a cross-section of sediments which was the site of previous excavations for the koala, predatory bird, and thylacine specimens were found. Aside from the ancient lizard, the expedition also yielded remains of fishes, platypuses, dolphins, and crocodiles on the site.

Dr. Kailah Thorn, lead author of the study and a palaeo-herpetologist (focused on the study of extinct reptiles and amphibians), recalls the extreme temperatures and hard work required to dig through the layers of clay in the site in a news release from Flinders. "But it was definitely worth it once the tiniest of bone fragments turned out to be those of the oldest Australian skink," she adds.

Finding Lizard Bones in Large Areas

The interior lands of Australia - previously green with life - have been widely considered as the cradle of its animal biodiversity, and the same applies to reptiles.

Thorn also notes that fossil lizards are usually too small to be identified out in the field, further explaining that lizard skulls are composed of more than twenty different bones that start to "disarticulate" once they start fossilizing. She further explains that they were able to locate these tiny fossils "in an area the size of one million soccer fields" was made possible by understanding the geology of the area, closing in on fossiliferous bands of silt that are recovered and sorted at the laboratory.

"These lizard fossils owe their discovery to the patient sorting of tiny bones," notes vertebrate paleontologist Trevor Worthy, lead author and an associate professor at Flinders. He stresses that a teaspoonful of deposit could hold hundreds of small bones, discovered under microscopes.

"Once every 30 spoons something else is found among the fish-usually a tiny mammal tooth. But the 2017 discovery of the oldest skink was a golden moment for a paleontologist," Worthy adds.