Fossil of ancient lizard-like creature unearthed in Australia

Reportedly, temnospondyls amphibians survived two of Earth's five mass extinction events. 

Palaeontologist Lachlan Hart, who led this fossil examination, mentioned that “we don’t often find skeletons with the head and body still attached, and the soft tissue preservation is an even rarer occurrence.”

The extinct thrived in the freshwaters of Sydney

During the Triassic period, about 240 million years ago, the giant carnivorous amphibian thrived in freshwater rivers of the present-day Sydney Basin. The ancient creature hunted fish such as Cleithrolepis. 

“Superficially, Arenaerpeton looks a lot like the modern Chinese Giant Salamander, especially in the shape of its head. 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,” said Hart. 

Arenaerpeton measured roughly around 3.9 feet (1.2 meters) from head to tail. While other closely related animals that coexisted with this species were most likely smaller in size. 

“The last of the temnospondyls were in Australia 120 million years after Arenaerpeton, and some grew to massive sizes. The fossil record of temnospondyls spans across two mass extinction events, so perhaps this evolution of increased size aided in their longevity.”

The paleontologists mention that the latest findings could "rewrite the evolution of amphibians in Australia." This remarkable fossil will be on exhibit later this year at the Australian Museum in Sydney.

The study was published in the Journal of Vertebrate Paleontology. 

Study abstract:

Compared with other Mesozoic tetrapod groups, chigutisaurid fossils from Australia are rare, with only three named taxa described from the continent. From Queensland, Keratobrachyops australis is known from the Triassic, and Siderops kehli from the Jurassic. Koolasuchus cleelandi, from the Cretaceous of Victoria, represents the youngest-known temnospondyl globally. Here we describe the first chigutisaurid from New South Wales, from the Early–Middle Triassic Terrigal Formation. The specimen (AM F125866) comprises an articulated, near-complete skeleton, presented in ventral aspect, as well as outlines of soft tissue. The new taxon preserves features that indicate an affinity with Chigutisauridae, confirming previous hypotheses on the presence of large-bodied chigutisaurids in the Triassic of Australia. The new Terrigal chigutisaurid is only the second chigutisaurid known from the Lower Triassic and fourth from Australia overall. The distribution of brachycephalic temnospondyls throughout the Mesozoic suggests specific adaptations led to the long-term survival of chigutisaurids, especially across the end-Triassic extinction event.