Fossils of this snake, dubbed Najash, show how the flexible skull of snakes evolved from lizard ancestors, a statement said.
Flinders University scientists were part of an international team that carried out CT scans and light microscopy of preserved skulls of Najash. The research was published in the journal Science Advances.
Dr Alessandro Palci, of the College of Science and Engineering at Flinders, said: "Snakes are famously legless, but then so are many lizards. What truly sets snakes apart is their highly mobile skull, which allows them to swallow large prey.
“Najash has the most complete, three-dimensionally preserved skull of any ancient snake, and this is providing an amazing amount of new information on how the head of snakes evolved.
"It has some, but not all of the flexible joints found in the skull of modern snakes. Its middle ear is intermediate between that of lizards and living snakes and, unlike all living snakes, it retains a well-developed cheekbone, which again is reminiscent of that of lizards.”
Flinders University and South Australian Museum researcher Professor Mike Lee, who was also part of the study, added: “Najash shows how snakes evolved from lizards in incremental evolutionary steps, just like Darwin predicted.”
The new snake family tree also shows that snakes possessed small, but perfectly formed, hind legs for the first 70 million years of their evolution.
The study was led by Fernando Garberoglio at Universidad Maimónides in Buenos Aires, with collaborators M.W. Caldwell at University of Alberta, Dr Alessandro Palci and Professor Mike Lee at Flinders University and the South Australian Museum in Adelaide, R.O. Gómez at Universidad de Buenos Aires, R.L. Nydam at Midwestern University Arizona; H.C.E. Larsson at McGill University and T.R. Simões at Harvard University.