Pitch-black darkness. Crushing squeezes, muddy passages, icy waterfalls. Bats and spiders. Abseiling over ledges into the unknown. How far would you go for a fossil? On a two-year retrieval mission of almost 60 hours in an underground cave, we met our limits—and went past.
The limestone slope of Potholes Cave Reserve is present in Gunaikurnai Nation, north of the township of Buchan in japanese Victoria, Australia. Right here, the river valley is peppered with shadowy entrances to underground caves. Portals barely giant sufficient to allow a keen caver open into kilometers of subterranean passages encrusted with delicate crystals twinkling in torchlight.
In one among them, Nightshade Cave, the Museums Victoria Research Institute led a staff of leisure cavers and Parks Victoria rangers to excavate a rare fossil: a near-complete skeleton of the extinct short-faced kangaroo Simosthenurus occidentalis. In June this 12 months, it’s going to seem on show at Melbourne Museum.
It began with an uncommon cranium
As is so typically the case in palaeontology, the invention started with engaged residents out in nature. In 2011, a neighborhood caving group first entered Nightshade Cave by a gap beforehand blocked by soil. One of many group, Joshua Van Dyk, sighted an uncommon animal cranium.
Recognising its potential significance, he reported the discover to Melbourne Museum. Nevertheless, Van Dyk reckoned it was irretrievable, showing to be crushed below boulders in a slim vertical collapse. The cave was gated shut to guard its contents and a decade handed quietly. In 2021, I took an curiosity within the intriguing discover. Members of the Victorian Speleological Association have been solely too completely satisfied to help a return to the cave.
Rigging a ropeline, we abseiled down a good 10-meter (32.8-foot) rift, emptying our lungs to move tight factors in midair. We corkscrewed right into a slim passage and wormed, single-file, by low-domed chambers hung with dripping stalactites and plastered by popcorn-like calcite formations.
Descending deeper, the cave reworked into tall, slim, clean-walled rifts, stuffed with darkish recesses. Hours handed as we circuited the passages, till a shout echoed round: discovered once more! We scrambled to a chimney-like chute stacked with pinned boulders, to come back eye to eye with an historical.
On reaching it, I felt sudden grief: the gorgeous fossilised cranium had within the intervening years begun to break down. It appeared that, regardless of its lengthy survival, the fossil was newly susceptible—from little greater than the altered air currents and altering humidity brought on by the brand new cave entrance. We strengthened the uncovered bones with protecting resins, however exited the cave having left them in place; extra time could be wanted to plan their retrieval.
A painstaking retrieval
On our return journeys, I rigorously brushed away fantastic layers of mud and we photographed and packed the newly freed fossils. The cranium had a deep muzzle, with sturdy jaws and tooth that marked it as a short-faced (sthenurine) kangaroo.
Behind it have been extra bones. It was a marvel to see vertebrae, shoulders and hips, limbs and a slim ribcage: lots of the bones have been wholly undisturbed and nonetheless of their unique positions. This was a single animal, not a random scattering of bones. It felt like a fossil holy grail.
An in depth comparability to fossils within the Museums Victoria State Assortment gave our skeleton its identification as Simosthenurus occidentalis. Comprising 150 preserved bones, it’s the most full fossil skeleton present in a Victorian cave so far.
That it’s a juvenile slightly than grownup kangaroo additional distinguishes it from different examples of the species. Its tooth present little put on, its cranium bones are nonetheless unfused, and its limb ends had not but joined, suggesting it was nonetheless younger at its time of dying.
From the size of its limbs, we estimate it weighed round 80 kilograms (176 kilos)—as a lot as a median individual—however may need grown half as giant once more had it reached maturity.
Australia’s extinct megafauna
Brief-faced kangaroos seem in Australia’s fossil document from 10 to fifteen million years in the past, as widespread rainforests started to provide strategy to drier habitats. They turned notably numerous through the shift towards our present arid local weather within the later a part of the Pleistocene Epoch, from round 500,000 years in the past.
However in a pulse of extinction around 45,000 years ago, they vanished throughout the continent, together with as much as 85% of Australia’s megafauna. Radiocarbon relationship by the Australian Nuclear Science & Technology Organisation dated the skeleton’s burial to 49,400 years in the past. This implies our S. occidentalis was among the many final of its sort.
At this time, the hills of japanese Gippsland host a valuable inhabitants of the brush-tailed rock-wallaby, a susceptible species. As soon as, they shared the nation with bigger kin.
A key concept below investigation is whether or not sthenurine kangaroos walked with a striding gait, rather than hopped. The skeleton we discovered has a uniquely full vertebral column, offering new insights we couldn’t get from remoted bones. With the good thing about detailed 3D fashions, this near-complete skeleton can be studied from anyplace on this planet.
This fossil, together with others from Nightshade Cave, is now housed and cared for in perpetuity at Melbourne Museum. By means of Museums Victoria Analysis Institute, we are able to protect a hyperlink to its as soon as house of East Gippsland, whereas opening a door to international analysis.
Tim Ziegler, Assortment Supervisor, Vertebrate Palaeontology, Museums Victoria Research Institute. This text is republished from The Conversation below a Inventive Commons license. Learn the original article.