Two-Year Dig Yields Stunning Kangaroo Fossil From Deep Underground Caves

Pitch-black darkness. Crushing squeezes, muddy passages, icy waterfalls. Bats and spiders. Abseiling more than ledges into the unknown. How far would you go for a fossil? On a two-year retrieval mission of practically 60 hours in an underground cave, we met our limits—and went beyond.

The limestone slope of Potholes Cave Reserve is located in Gunaikurnai Nation, north of the township of Buchan in eastern Victoria, Australia. Right here, the river valley is peppered with shadowy entrances to underground caves. Portals barely significant sufficient to permit a prepared caver open into kilometers of subterranean passages encrusted with delicate crystals twinkling in torchlight.

In one particular of them, Nightshade Cave, the Museums Victoria Study Institute led a group of recreational cavers and Parks Victoria rangers to excavate an extraordinary fossil: a close to-comprehensive skeleton of the extinct brief-faced kangaroo Simosthenurus occidentalis. In June this year, it will seem on show at Melbourne Museum.

It began with an uncommon skull

As is so typically the case in palaeontology, the discovery started with engaged citizens out in nature. In 2011, a neighborhood caving group very first entered Nightshade Cave by means of an opening previously blocked by soil. One particular of the group, Joshua Van Dyk, sighted an uncommon animal skull.

Recognising its prospective significance, he reported the come across to Melbourne Museum. Having said that, Van Dyk reckoned it was irretrievable, appearing to be crushed beneath boulders in a narrow vertical collapse. The cave was gated shut to safeguard its contents and a decade passed quietly. In 2021, I took an interest in the intriguing come across. Members of the Victorian Speleological Association had been only also satisfied to help a return to the cave.

Rigging a ropeline, we abseiled down a tight ten-meter (32.eight-foot) rift, emptying our lungs to pass tight points in midair. We corkscrewed into a narrow passage and wormed, single-file, by means of low-domed chambers hung with dripping stalactites and plastered by popcorn-like calcite formations.

Descending deeper, the cave transformed into tall, narrow, clean-walled rifts, complete of dark recesses. Hours passed as we circuited the passages, till a shout echoed about: located once more! We scrambled to a chimney-like chute stacked with pinned boulders, to come eye to eye with an ancient.

On reaching it, I felt sudden grief: the attractive fossilised skull had in the intervening years begun to collapse. It seemed that, in spite of its lengthy survival, the fossil was newly vulnerable—from small additional than the altered air currents and altering humidity brought on by the new cave entrance. We strengthened the exposed bones with protective resins, but exited the cave getting left them in spot additional time would be necessary to program their retrieval.

A painstaking retrieval

On our return trips, I meticulously brushed away fine layers of mud and we photographed and packed the newly freed fossils. The skull had a deep muzzle, with robust jaws and teeth that marked it as a brief-faced (sthenurine) kangaroo.

Behind it had been additional bones. It was a marvel to see vertebrae, shoulders and hips, limbs and a narrow ribcage: several of the bones had been wholly undisturbed and nonetheless in their original positions. This was a single animal, not a random scattering of bones. It felt like a fossil holy grail.

A detailed comparison to fossils in the Museums Victoria State Collection gave our skeleton its identification as Simosthenurus occidentalis. Comprising 150 preserved bones, it is the most comprehensive fossil skeleton located in a Victorian cave to date.

That it is a juvenile rather than adult kangaroo additional distinguishes it from other examples of the species. Its teeth show small put on, its skull bones are nonetheless unfused, and its limb ends had not however joined, suggesting it was nonetheless young at its time of death.

From the size of its limbs, we estimate it weighed about 80 kilograms (176 pounds)—as significantly as an typical person—but may well have grown half as significant once more had it reached adulthood.

Australia’s extinct megafauna

Brief-faced kangaroos seem in Australia’s fossil record from ten to 15 million years ago, as widespread rainforests started to give way to drier habitats. They became specifically diverse through the shift toward our present arid climate in the later component of the Pleistocene Epoch, from about 500,000 years ago.

But in a pulse of extinction about 45,000 years ago, they vanished across the continent, along with up to 85% of Australia’s megafauna. Radiocarbon dating by the Australian Nuclear Science &amp Technologies Organisation dated the skeleton’s burial to 49,400 years ago. This indicates our S. occidentalis was amongst the incredibly final of its type.

Right now, the hills of eastern Gippsland host a valuable population of the brush-tailed rock-wallaby, a vulnerable species. After, they shared the nation with bigger kin.

A crucial concept beneath investigation is whether or not sthenurine kangaroos walked with a striding gait, rather than hopped. The skeleton we located has a uniquely comprehensive vertebral column, delivering new insights we couldn’t get from isolated bones. With the advantage of detailed 3D models, this close to-comprehensive skeleton can also be studied from anyplace in the globe.

This fossil, along with other folks from Nightshade Cave, is now housed and cared for in perpetuity at Melbourne Museum. By means of Museums Victoria Study Institute, we can preserve a hyperlink to its when household of East Gippsland, though opening a door to worldwide study.

Tim Ziegler, Collection Manager, Vertebrate Palaeontology, Museums Victoria Study Institute. This short article is republished from The Conversation beneath a Inventive Commons license. Study the original short article.