Beneath the world's largest limestone plateau, caves preserve the last meals of marsupial lions and reveal megafauna survived 40,000 years longer than we thought.
A Plateau of Pitfalls
The Nullarbor Plain is the largest single piece of limestone on Earth, a vast, semi-arid plateau covering 200,000 square kilometers. Its name, derived from the Latin for "no trees," aptly describes the sparse vegetation on its surface. But beneath this flat expanse lies a complex world. Over millions of years, rainwater has seeped through the porous limestone, dissolving the rock to create a massive karst landscape of sinkholes, blowholes, and thousands of caves.
These caves became perfect traps. Unwary animals wandering the plain could fall through a surface opening—a collapsed doline or sinkhole—into a cavern below. The cool, dry, and stable environment of the caves then preserved their skeletons with incredible fidelity. Some fossil skeletons are found fully articulated, appearing as if the animal only recently died, when in fact they can be hundreds of thousands of years old. This exceptional preservation makes the Nullarbor caves a record of Australia's past ecosystems.
The Lion's Den
Among the most spectacular finds are the remains of Australia's apex predator, Thylacoleo carnifex, the marsupial lion. Roughly the size of a modern leopard but with a heavier, bear-like build, this powerful carnivore possessed a bite force stronger than any known mammal, living or extinct. Instead of canine teeth, it had massive, blade-like premolars that functioned like bolt-cutters to slice through flesh, and a large, retractable claw on each thumb likely used to disembowel prey.
Caves such as Flight Star Cave and the appropriately named Thylacoleo Cave have yielded complete skeletons of these formidable predators. Multiple individuals, including mothers with young, suggests they used the caves as dens. Found alongside the Thylacoleo bones are the remains of their prey, including giant short-faced kangaroos like Procoptodon goliah, which could grow up to 3 meters tall. Some of these prey bones show distinctive v-shaped incisions, clear evidence of being sliced by Thylacoleo's unique teeth.
A New Extinction Timeline
For decades, the scientific consensus held that Australia's megafauna—animals over 45 kilograms—largely vanished by about 42,000 years ago, shortly after the arrival of humans. The discoveries on the Nullarbor Plain challenge this timeline. The region appears to have been a refugium, a place where stable conditions allowed multiple species to persist long after they disappeared from other parts of the continent.
While many fossils date to the mid-Pleistocene (around 130,000-780,000 years ago), some remains are significantly younger. Discoveries at sites like Cuddie Springs have placed megafauna alongside human tools as recently as 30,000 to 35,000 years ago, suggesting a much longer period of coexistence. The Nullarbor fossils provide a critical, high-fidelity record that helps scientists piece together a clearer picture of extinction—one potentially driven by a mosaic of climate change and human pressures over many millennia. The caves preserve bones and a detailed environmental history in stalactites and stalagmites that records ancient climate and vegetation.
💡Fun Facts
Pound for pound, the marsupial lion (*Thylacoleo carnifex*) had the most powerful bite of any mammal ever recorded. A 101 kg specimen could bite with the force of a 250 kg African lion.
The Nullarbor Plain is the world's largest continuous area of limestone, covering about 200,000 square kilometers.
Some Nullarbor caves are known as "blowholes" because they "breathe." Changes in atmospheric pressure cause winds of up to 70 km/hr to rush in or out of small surface openings.
Besides marsupial lions, the caves contain fossils of giant kangaroos, massive wombat-like *Diprotodons*, and the huge flightless bird *Genyornis*.
The fossil caves are not open to the public. They are remote, dangerous, and scientifically protected sites. A few select caves, like the Murrawijinie Caves, are accessible to the public for viewing.
Admission
Access to the Nullarbor National Park and designated lookouts is generally free.
Accessibility
The Nullarbor Plain is crossed by the sealed Eyre Highway. Access to specific features like the Murrawijinie Caves is via unsealed tracks, which may require a 4WD vehicle depending on conditions. Access to the cliff edges is restricted to three official, safe lookouts.