Deep black darkness. Oppressive narrow spaces, muddy passages, icy waterfalls. Bats and spiders. Abseiling over rocky ledges into the unknown. How far would you go for a fossil? During a two-year, almost 60-hour recovery mission in an underground cave, we pushed ourselves to our limits – and went beyond them.
The limestone slope of Potholes Cave Reserve occurs in Gunaikurnai Country north of Buchan township in eastern Victoria, Australia. Here the river valley is dotted with shadowy entrances to underground caves. Portals barely large enough to allow a willing spelunker access to miles of underground passages covered in delicate crystals sparkling in the torchlight.
In one of them, the Nightshade Cave, is located Museums Victoria Research Institute led a team of recreational cavers and Park Victoria rangers to unearth an extraordinary fossil: a almost complete skeleton of the extinct short-nosed kangaroo Western Simosthenurus. It will go on display at the Melbourne Museum in June this year.
It started with an unusual skull
As is often the case in paleontology, discovery began with engaged citizens in nature. In 2011, a local caving group entered Nightshade Cave for the first time through an opening that had previously been blocked by earth. One of the group, Joshua Van Dyk, spotted an unusual animal skull.
He recognized the potential significance and reported the find to the Melbourne Museum. However, Van Dyk assumed it was irretrievable as it appeared to have been crushed under boulders in a narrow vertical collapse. The cave was sealed with a gate to protect its contents, and a decade passed quietly. In 2021, I became interested in the fascinating find. Members of Victorian Speleological Association were only too happy to assist in returning to the cave.
Using a rope line, we rappelled down a narrow, 10-meter (32.8-foot) gap, emptying our lungs to pass through narrow spaces in the air. We squeezed into a narrow passageway and snaked single file through low, vaulted chambers hung with dripping stalactites and covered in popcorn-like calcite formations.
The deeper she descended, the more the cave transformed into high, narrow, clean-walled crevices full of dark niches. Hours passed as we circled the hallways until a shout echoed around us: Found again! We climbed to a chimney-like slide stacked with pinned boulders to come face to face with an ancient human.
When I got there, I felt a sudden sadness: the beautiful petrified skull had begun to collapse in recent years. It appeared that despite its long survival, the fossil was recently vulnerable – only due to the changed air currents and humidity caused by the new cave entrance. We reinforced the exposed bones with protective resins, but left the cave after leaving them in place; More time would be needed to plan their repatriation.
A tedious search
On our return trips, I carefully wiped away fine layers of mud and we photographed and packaged the freshly uncovered fossils. The skull had a deep snout with powerful jaws and teeth that identified it as a short-faced (sthenurine) kangaroo.
There were more bones behind it. It was a wonder to see vertebrae, shoulders and hips, limbs and a narrow ribcage: many of the bones were completely undamaged and still in their original positions. It was a single animal and not a random collection of bones. It felt like a fossil holy grail.
A detailed comparison with fossils in the museum’s Victoria State Collection resulted in the identification of our skeleton Western Simosthenurus. With 150 bones preserved, it is the most complete fossil skeleton yet found in a Victorian cave.
The fact that it is a juvenile rather than an adult kangaroo further distinguishes it from other specimens of this species. Its teeth show little signs of wear, its skull bones are not yet fused, and the ends of its limbs were not yet connected, suggesting that it was at that time was still young when he died.
By the size of his limbsWe estimate it weighed about 80 kilograms (176 pounds) – the same as an average human – but would have been perhaps half that size in adulthood.
Australia’s extinct megafauna
Short-faced kangaroos appear in Australia’s fossil record as early as 10 to 15 million years ago, when extensive rainforests began to give way to drier habitats. They became particularly diverse during the shift to our current dry climate in the later part of the Pleistocene, around 500,000 years ago.
But in a pulse of extinction about 45,000 years agoThey disappeared across the continent, along with up to 85% of Australia’s megafauna. Radiocarbon dating by the Australian Nuclear Science and Technology Organization dated the burial of the skeleton to 49,400 years ago. This means ours Western St was among the very last of its kind.
Today the hills of east Gippsland are home to a valuable population of these animals Brush-tailed rock wallabyan endangered species. They once shared the land with larger relatives.
A key idea currently being investigated is whether sthenic kangaroos walked with a striding gait. instead of jumping. The skeleton we found has a uniquely complete spine and provides new insights that we were unable to gain from isolated bones. Thanks to detailed 3D models, this almost complete skeleton can also be examined from anywhere in the world.
This fossil, along with other fossils from Nightshade Cave, will now be permanently preserved and cared for Melbourne Museum. Through the Museums Victoria Research Institute we can maintain a connection to its former home of East Gippsland while opening a door to global research.
Tim ZieglerHead of Collection, Vertebrate Paleontology, Museums Victoria Research Institute. This article was republished by The conversation under a Creative Commons license. read this original article.