Giant 240-Million-Year-Old “Sand Creeper” Discovered in Retaining Wall

In an incredible twist of fate, a retired chicken farmer unearthed a 240-million-year-old amphibian fossil in a pile of rocks meant for a garden wall, leading to one of the most extraordinary paleontological finds in New South Wales.

Ancient Fossil Discovery in a Backyard Wall

A fossilized amphibian that dates back 240 million years has now been officially named and described by researchers from UNSW Sydney and the Australian Museum. The discovery was first made in the 1990s when a retired chicken farmer collected stones from a local quarry to build a garden retaining wall. Among those rocks was a remarkable fossil, which was later donated to the Australian Museum in Sydney.

The fossil belongs to a newly identified species called Arenaerpeton supinatus, meaning “supine sand creeper.” According to palaeontologist Lachlan Hart, who works with both UNSW Science and the Australian Museum, the specimen includes most of the skeleton and, unusually, also preserves the outlines of its skin.

Bones, Skin, and a Peek Into the Past

“This fossil is a unique example of a group of extinct animals known as temnospondyls, which lived before and during the time of 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 the head and body still attached, and the soft tissue preservation is an even rarer occurrence.”

Arenaerpeton lived in freshwater river systems that once flowed through the Sydney Basin during the Triassic period. Mr. Hart believes it likely preyed on ancient fish such as Cleithrolepis, although little else is known about the other creatures it may have coexisted with at the time.

A Hefty Creature With Fierce Features

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

“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.”

Mr. Hart says what is exciting about the discovery is that Arenaerpeton is large, estimated to be about 1.2m from head to tail, when most other closely related animals that lived at the same time were small.

Evolution Through Extinction Events

“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.”

Dr. Matthew McCurry, Senior Lecturer in UNSW’s School of BEES and Curator of Palaeontology at the Australian Museum says the fossil is a significant find in Australian paleo history.

“This is one of the most important fossils found in New South Wales in the past 30 years, so it is exciting to formally describe it,” says Dr. McCurry, who is also a co-author on the study. “It represents a key part of Australia’s fossil heritage.”

The study has been published in the Journal of Vertebrate Paleontology.

Reference: “A new chigutisaurid (Brachyopoidea, Temnospondyli) with soft tissue preservation from the Triassic Sydney Basin, New South Wales, Australia” by Lachlan J. Hart, Bryan M. Gee, Patrick M. Smith and Matthew R. McCurry, 3 August 2023, Journal of Vertebrate Paleontology.
DOI: 10.1080/02724634.2023.2232829

A version of this article was originally published in August 2023.

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