Undergraduate student volunteer Nick Wiggins (UQ) excavating at Colosseum Chamber
Recently I wrote about an ongoing study at Colosseum Chamber, an extensive fossil deposit located at the Capricorn Caves tourist park, just north of Rockhampton in central eastern Queensland. The chamber occurs within an ancient cavernous limestone, which itself dates back to the Devonian (over 350 million years ago). The Colosseum deposit is around 2 m deep and, to put it simply, is chockfull of the fossilised remains of an ancient feast. The bones are the leftovers – the undigested parts – from the feeding activities of owls over the past several thousand years. The fossils consist of a huge number of teeth, jaws, and post-cranial skeletal elements from a range of small-bodied species such as frogs, skinks, bandicoots, dunnarts, antechinuses, planigales, possums, and rodents.
Having first identified the deposit back in the mid-2000’s, we were lucky enough to obtain some recent research funding from the Ian Potter Foundation, The University of Queensland and Australian Research Council to continue our excavations. In mid-April, we ventured out for a new fieldtrip to the site.
Lower jaw of brushtail possum from the Colosseum Chamber fossil deposit
The trip was led by Dr Julien Louys from UQ with me as second-in-charge, and we were joined by other colleagues from UQ, the Queensland Museum, and volunteers including PhD student Jonathan Cramb (QUT) and undergraduate student Nick Wiggins (UQ). Although these were the folk who did most of the digging, the trip just would not have been possible without the generous support of the Capricorn Caves tourist park who put us up and allowed access to the cave, and local cavers, Noel and Jeanette Sands who also assisted with the excavations (Noel also cooked up an awesome barbie for my last night in town!).
From our preliminary dating study, we know that the deposit accumulated over the last 80 thousand years. This is a particularly exciting time period to be investigating. The last 80 thousand years included an episode of great climatic upheaval, numerous species extinctions, and was also the time that saw humans first set foot on the continent. The goal of our work is to use the Colosseum Chamber
Maxilla of southern brown bandicoot from Colosseum Chamber. The species is extinct from the region today.
fossil record to explore how the local faunas reacted to such prehistoric events. Having a robust understanding of species response(s) to past environmental perturbations is absolutely fundamental in informing modern conservationists and climate scientists about the possible effects of climate change on living populations.
Previously we had excavated the deposit to a depth of around 90 cm from the modern cave floor. This year we were able to extend the dig much deeper, to almost 2 metres deep. The digging got quite difficult the further down we got- both logistically (it’s not particularly comfortable working in such a cramped environment with other sweaty, smelly palaeontologists!), and because we hit a lot of large chunks of limestone, signalling that we were getting close to the bottom of the deposit.
Lower jaw of an extinct rabbit rat, recently discovered by PhD student Jonathan Cramb
Thousands of kilograms of sediment were removed from the cave in buckets and were taken down to the bottom of the ridge for sieving. Digging is fun, but the sieving is where you get to see all the amazing fossils that the deposit contains. Jonathan, our resident rodent expert, recently discovered a new fossil species of Rabbit Rat from Colosseum Chamber (named Conilurus capricornensis– the species name is in honour of the Capricorn Caves tourist park), and was extremely excited to see a whole heap more of his unusual rodent emerge from the sieving!
During the trip we were able to collect new samples for dating including charcoal (radiocarbon dating), straw stalactites (uranium-series dating) and sediment (optically stimulated luminescence dating). Getting those samples dated is now the next major job, not to mention the huge amount of bones that need to be taxonomically identified and sorted into skeletal groups. No doubt we have a mammoth task in front of us, but the information that we can potentially extract from the deposit is just so critical and important for modern conservation that we just can’t ignore it. Updates to come!
