The Tracks That Proved a Continent Once Touched Antarctica: Victoria's Genoa River Tetrapod Footprints

A slab of grey sandstone in eastern Victoria holds the footprints of an animal that walked through mud 350 million years ago. The impressions are small, about the size of a child's hand, and they do not look like the tracks of a fish or a reptile. They are the earliest evidence of four-legged land animals ever found in the Southern Hemisphere.

A Discovery in River Rock

The tracks were found in 2024 near the Genoa River, close to the New South Wales border, in a formation called the Snowy Plains Volcanics. The rock was laid down in the Devonian-Carboniferous transition, roughly 350 million years ago, when the continents were arranged very differently.

At that time, what is now eastern Australia sat near the South Pole, connected to Antarctica as part of the supercontinent Gondwana. The climate was cool, but not frozen. Rivers and floodplains stretched across the landscape, and the first tetrapods—vertebrates with four limbs—were beginning to explore land.

The Genoa River footprints are not the oldest tetrapod tracks in the world; those belong to Poland and Scotland, dating to around 390 million years ago. But they are the oldest in Australia by tens of millions of years, and they fill a gap in the global record of how animals moved from water to land.

Reading the Impressions

The footprints are preserved in fine-grained sandstone, originally deposited as silt on a riverbank or floodplain. The mud was soft enough to take an impression but firm enough to hold its shape, and later sediments filled the tracks, creating natural casts.

Paleontologists identified five distinct tracks, each showing the imprint of a foot with four or five digits. The spacing between prints suggests the animal was small, perhaps 30 to 40 centimetres long, and walked with a sprawling gait not unlike a modern salamander.

What makes the tracks significant is not their size but their location. Most Devonian tetrapod fossils come from the Northern Hemisphere—Greenland, Scotland, Pennsylvania. The Genoa River footprints prove that tetrapods had reached high southern latitudes by the end of the Devonian, and that their dispersal was global.

A Continent on the Move

The Genoa River site also records the slow separation of continents. The sandstone that preserves the footprints was once part of a continuous basin that extended into what is now Antarctica. When Gondwana broke apart, the basin split, and the tracks ended up in Australia.

Similar Devonian rocks occur in the Beacon Supergroup of Antarctica's Transantarctic Mountains, and geologists have long suspected that the two landmasses share a geological history. The footprints provide a tangible link: the same animals likely walked across both, leaving traces that later drifted thousands of kilometres apart.

The tracks are a kind of fossilised handshake between continents, a reminder that Australia's eastern coast was once the edge of a much larger land.

What Came Before

Tetrapods evolved from lobe-finned fishes, animals like Tiktaalik from the Canadian Arctic, which had fins with bones that could support weight. The transition took place in shallow, oxygen-poor waters where the ability to crawl onto land offered advantages—access to new food sources, escape from predators, or travel between drying ponds.

The Genoa River footprints do not tell us which species made them; no bones were found nearby. But the tracks capture a moment in that transition, a small animal hauling itself across a muddy bank in a polar landscape, leaving marks that would outlast the continent it walked on.

The Larger Record

Australia's fossil record of early tetrapods is sparse. For decades, the only Devonian tetrapod material from the continent was a single jawbone fragment from New South Wales, discovered in the 1970s. The Genoa River tracks add a second data point and a more complete picture of behaviour.

They also raise questions. If tetrapods lived in polar Gondwana, they must have coped with months of darkness each winter. Did they hibernate? Did they migrate? Did they simply adapt to low-light conditions? The tracks cannot answer these questions, but they place them in a new geographic context.

The same basin that preserved the footprints also contains fossilised plants and fish, suggesting a rich ecosystem. Club mosses and horsetails lined the riverbanks. Lungfish and placoderms swam in the channels. And on the mudflats, the first four-legged animals left their mark.