Chicken farmer discovered a new, very dead giant amphibian

Palaeontologists at UNSW have confirmed that a retired chook farmer discovered a new species of amphibian three decades ago. The fossil was encrusted in rocks bought for a retaining wall.

When farmer Mihail Mihailidis discovered that one of the rocks he’d sourced from a New South Wales Central Coast quarry contained fossilised remains of an unknown animal, he donated the slab to the Australian Museum.

Arenaerpeton supinatus fossil.
Arenaerpeton supinatus fossil. Credit: Supplied, UNSW Sydney/Richard Freeman

Apart from its display in a 1997 exhibition, the fossil has remained locked away from view in the museum’s archives. Now, the identity of the 240-million-year-old fossil has been revealed.

Arenaerpeton supinatus, which means “supine sand creeper” inhabited freshwater rivers around the vast Sydney Basin region, which today sprawls from Newcastle to Wollongong and inland toward the Blue Mountains. It belongs to the order Temnospondyli, a diverse group of primitive 4-limbed vertebrates known as tetrapods.

Palaeontologist Lachlan Hart, who named the fossil, likened its shape – including flattened head and large body – to the Chinese giant salamander (Andrias davidianus), which is found in the Yangtze River basin, in central China.

An artist’s imagining of the 1.2-metre-long A. supinatus was aided by the outline of its skin, something which is uncommon in such fossils.

“We don’t often find skeletons with the head and body still attached, and the soft tissue preservation is an even rarer occurrence,” says Hart, whose description of the animal appears in the Journal of Vertebrate Paleontology.

Fossil 120
Lachlan Hart with the A. supinatus fossil. Credit: UNSW Sydney/Richard Freeman

“However, from the size of the ribs and the soft tissue outline preserved on the fossil, we can see that it was considerably more heavyset than its living descendants.

“It also had some pretty gnarly teeth, including a pair of fang-like tusks on the roof of its mouth.”

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