Fossils of new species of skinks discovered in Australia

A new species of extinct skink that lived in the Oligocene era has been identified from fossilized remains found in South Australia.

The swamp skink (Lissolepis coventryi), which is probably the most similar living lizard to Proegernia mikebulli. Image credit: Mark Hutchinson, South Australian Museum & Flinders University.

The newly identified species lived around 25 million years ago, making it the known skink of Australia.

Appointed Proegernia mikebulli, it belongs to Egerniinae, a large subfamily of social skinks – including bluetongue, sleeping lizards (shingles), ground mules, and spiny-tailed skinks – within the family Scincidae.

“The species is named after Professor Michael Bull of Flinders University, South Australia, who has spent decades documenting the ecology of Australian egerniine skinks,” said lead author Dr Kailah. Thorn, a paleoherpetologist at the South Australian Museum and Flinders University, and his colleagues.

Several incomplete jaws of the ancient lizard were recovered from the Namba Formation outcropping at Pinpa Lake and Billeroo Creek, a seven hour drive north of the capital Adelaide.

The fossiliferous deposits of this formation also support abundant aquatic resources (such as fish, the giant platypus Obdurodon and waterfowl) and terrestrial vertebrates (such as opossums, dasyuromorphs and skinks).

The fossilized remains of Proegernia mikebulli.  Abbreviations: adf - adductor fossa;  anf - angular facet;  art.  - articular;  D.  - dental;  gl - glenoid fossa;  iaf - inferior alveolar foramen;  mg - Meckel's sulcus;  psf - posterior surangular foramen;  rap - retroarticular process;  san.  - surangular;  and sy - symphysis.  Image credit: Thorn et al., Doi: 10.1098 / rsos.201686.

The fossilized remains of Proegernia mikebulli. Abbreviations: adf – adductor fossa; anf – angular facet; art. – articular; D. – dental; gl – glenoid fossa; iaf – inferior alveolar foramen; mg – Meckel’s sulcus; psf – posterior surangular foramen; rap – retroarticular process; san. – surangular; and sy – symphysis. Image credit: Thorn et al., doi: 10.1098 / rsos.201686.

“Some of Australia’s most famous animals including koalas and kangaroos can be traced back to their fossil ancestors in remarkable finds in central South Australia,” said Dr Thorn.

“The importance of this site containing the ancestors of the first Australian marsupials was already well established, but no fossil lizards had ever been found in the Namba formation.”

“It was 45 degrees Celsius in the shade that day and some hard work digging in the clay, but it was well worth it once the smallest of the bone fragments turned out to be the ones from the oldest Australian skink. “

“Fossil lizards are often too small to identify when you’re in the field, and lizard skulls are made up of over 20 individual bones that all fall apart when they fossilize,” added Dr Thorn.

“The discovery of tiny fossil lizards in an area the size of a million football fields was made possible by understanding the geology of the area and targeting bands of silt to sift and sort in the lab. “

The teams paper was published in the journal Royal Society Open Science.

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KM Thorn et al. 2021. A new kind of Proegernia the Namba Formation in South Australia and the early evolution and environment of Australian egerniine skinks. R. Soc. open science 8 (2): 201686; doi: 10.1098 / rsos.201686

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