Paleontologists have formally identified a 240-million-year-old giant amphibian fossil that spent decades hidden inside a suburban retaining wall in New South Wales, Australia. The specimen, now named Arenaerpeton supinatus or “supine sand creeper,” ranks among the most significant Triassic finds in the region.
Researchers from UNSW Sydney and the Australian Museum confirmed details of the discovery on May 6, 2026, per ScienceDaily. The fossil preserves not only bones but also an outline of the creature’s skin, offering rare insights into a freshwater predator from the Middle Triassic period.
A retired chicken farmer discovered the fossil in the 1990s while sourcing sandstone slabs from a local quarry for a garden retaining wall on the Central Coast north of Sydney, reported ABC News. He noticed unusual impressions on one slab, donated it to the Australian Museum, and it remained largely unstudied until recent analysis.
The creature, estimated at about 1.2 to 1.6 meters (4 to 5.2 feet) long, lived in ancient river systems of the Sydney Basin. It belongs to the temnospondyl group, distant relatives of modern salamanders. Scientists describe it as a robust predator with powerful jaws suited for freshwater environments, LiveScience.
Paleontologist Lachlan Hart, affiliated with UNSW Science and the Australian Museum, led the formal description. “It’s an incredibly rare find,” Hart said, noting the exceptional preservation that includes soft tissue outlines.
The sandstone block originated from formations typical of the Narrabeen Group. Rapid burial in a coastal or riverine setting helped preserve fine details. The species name Arenaerpeton supinatus translates to “supine sand creeper,” reflecting its position when found and its likely lifestyle, reported Mirage News.
This temnospondyl adds to the understanding of post-Permian recovery ecosystems in eastern Australia. Similar amphibians thrived after the mass extinction event around 252 million years ago, filling niches before dinosaurs came to dominate, reported SciTechDaily.
The fossil underwent CT scanning and detailed preparation at the Australian Museum. It will eventually go on public display. The find demonstrates how citizen discoveries contribute to science, as the original finder recognized its importance and preserved the slab.
Australian heritage laws protect the specimen, which remains state property, reported the National Post. No commercial transactions occurred. Researchers plan further studies on its evolutionary relationships to other Triassic amphibians.
