Fossils in Queensland
Capricorn Caves Prehistoric Past
When I first started volunteering at the Queensland Museum I was given a box full with hundreds of thousands of very tiny fossilised bones known as ‘microfossils’. These fossils belonged to a range of small-bodied vertebrate species such as frogs, lizards, birds, possums, bandicoots and rodents, just to name a few. These microfossils were excavated from a >100,000-5,000 year old cave deposit in Colosseum Chamber at Capricorn Caves near Rockhampton. My job was to carefully sort through these fossils, using fine brushes and tweezers, under a microscope and identify what part of the skeleton they came from and what species of animal they belonged to. What I didn’t know at the time was that I was essentially sorting through fossilised owl vomit and leftovers from Australia’s only carnivorous bat, the Ghost Bat (Macroderma gigas). The owls and bats would hunt their prey at night and bring them back to the cave to consume their meal. The bones are the undigested parts that owls regurgitate into pellets and become incorporated into the cave floor deposit over several thousand years. Bats are also very messy eaters and drop parts of their meal onto the ground. The bones of these small animals, ‘microfauna’, are very helpful when trying to understand the interactions between fossil species and their environment, ‘palaeoecology’, thousands of years ago.
Sorting through bones from Colosseum Chamber (left). Dig pit in Colosseum Chamber (right).
In 2012 my colleague, Dr Scott Hocknull (Queensland Museum), and I, discovered new fossil deposits at Capricorn Caves. As I was digging through sediment in a cave chamber I first pulled out a fossilised tooth belonging to a bandicoot that had lived in rainforests that once spread across north-eastern Queensland. Similar rainforest deposits have been found at nearby Mt Etna Caves National Park. Both Mt Etna and now Capricorn Caves contain the only definitely known Quaternary tropical rainforest vertebrate fossil record in Australia. Nearby we scrambled into a small chamber under a false floor and were amazed at what we saw above us. Our torches lit up a cave breccia that had cemented thousands upon thousands of bones into rock over several thousand years. This breccia contained fossils of a pig-footed bandicoot (Chaeropus sp.), a recently extinct species of bandicoot that once thrived in arid central Australia. For the first time at Capricorn Caves we had found evidence for a faunal succession from the oldest rainforest (>500,000-300,000 years ago) through to an arid ecology (>250,000-205,000 years ago) and finally to an environment similar to today (>100,000 years ago – present). These fossil deposits show the replacement and extinction of species impacted by environmental changes through time which have been initiated by climatic changes and eventually human activity
Excavating the rainforest deposit in Harp Chamber (left). Fossil breccia lining the ceiling of Fairy Chamber (right).
You can explore the cave’s prehistoric past and discover these amazing fossils deposits on the Fossil Tour at Capricorn Caves.
By Rochelle Lawrence, palaeontologist at Capricorn Caves