A 240 million-year-old fossil has finally been formally identified after being hidden behind a protective wall for decades. Researchers from UNSW Sydney and the Australian Museum have now named and described the ancient amphibian, drawing new attention to an unusual discovery that began in the 1990s.
This specimen was first uncovered by a retired chicken farmer who purchased rocks from a nearby quarry to build a garden protection wall. The stones also contained a fossil, which was later donated to the Australian Museum in Sydney.
Rare fossil preserves skeleton and skin
Lachlan Hart, a paleontologist affiliated with both UNSW Science and the Australian Museum, explains that the fossil, now named Aranerpeton supinatusmeaning ‘supine sand creeper’, is exceptionally well preserved. This includes almost the entire skeleton and even the faint outline of the animal’s skin.
“This fossil is a unique example of a group of extinct animals called temnospondyls, which lived before and during the dinosaurs,” says Mr Hart, a PhD candidate in the School of Biological, Earth and Environmental Sciences (BEES) at UNSW.
“We don’t often find skeletons with a fused head and body, and preservation of soft tissues is an even rarer phenomenon.”
A river hunter from the Triassic
Eranerpeton lived in freshwater environments in what is now the Sydney Basin during the Triassic period, about 240 million years ago. According to Mr Hart, it probably preyed on ancient fish like Clitherolepis. Furthermore, there is limited evidence about other species that share its habitat.
In appearance this creature may remind people of the modern Chinese giant salamander, especially given the shape of its head.
“Superficially, Eranerpeton resembles the modern Chinese giant salamander, especially in the shape of its head,” says Mr Hart.
“However, from the shape of the ribs and the outline of the soft tissue preserved on the fossil we can see that it was significantly heavier than its living descendants. It also had some beautiful teeth, including a pair of fangs on the roof of its mouth.”
size may have helped it survive
The most notable aspect of Arenaerpeton is its size. Mr Hart estimates it measured about 1.2 meters from head to tail, unusually large compared to many of its close relatives from the same period.
He notes that later temnospondyls continued to exist in Australia for another 120 million years, with some species reaching even larger sizes. This long history spans two major mass extinction events, which suggests that increased body size may have played a role in their survival.
A major fossil discovery in Australia
Dr Matthew McCurry, senior lecturer in UNSW’s School of BEES and curator of palaeontology at the Australian Museum, emphasizes the significance of the discovery.
“This is one of the most significant fossils found in New South Wales in the last 30 years, so it’s exciting to have it formally described,” says Dr. McCurry, who is also a co-author of the study. “It represents an important part of Australia’s fossil heritage.”
This research has been published in Vertebrate Paleontology Journal.