Research website of Dr Gilbert Price

Diprotodon’s big day out

The early stages of preparing the Diprotodon skull (photo: I. Sobbe)

The early stages of preparing the Diprotodon skull (photo: I. Sobbe)

I recently wrote about a giant Diprotodon skull that was discovered fossilised in Pleistocene-aged deposits on the Darling Downs. It is a monstrous skull, measuring around 90 cm in length, and discovered by a local simply walking along the creek. With the help of the discoverer, we excavated the skull, then my friend, Ian Sobbe, a local farmer and amateur palaeontologist, set to work preparing the skull.

Ian spent the best part of a year working on the specimen. Simply put, Ian did a cracking job. It’s a wonderfully preserved skull with exquisite detail. Ian used a combination of brushes, dental picks, scrapers, glues and other consolidants to remove the surrounding sediments and ensure that the skull wouldn’t crack and break as it dried out.

The Diprotodon skull nearly finished (photo: I. Sobbe)

The Diprotodon skull nearly finished (photo: I. Sobbe)

With the original discoverer’s blessing, the skull was donated to the Queensland Museum in September 2012. By having the skull in an institution like the Queensland Museum, it ensures that the specimen will be well-looked after and stored in the most appropriate conditions (temperature and humidity controlled storage and so on) to ensure its long-term preservation. The skull will most likely also go on display to the public sometime in the next year or so.

Ian and I have some big plans for the skull. We’d like to eventually write-up a description of the specimen and have it published in a peer-reviewed science journal. We are also working with a PhD student from Monash University, Alana Sharp, who is conducting a study on the nasals of the big guy.

Ian Sobbe and the Diprotodon

Ian Sobbe and the Diprotodon

I have also drilled tiny tooth samples from the skull that will allow me to directly date it using uranium-series methods (currently in preparation). I already have some radiocarbon dates for the skull, and hopefully soon, some optically-stimulated luminescence (OSL) dates by my colleague, Dr Kathryn Fitzsimmons (Max Planck Institute for Evolutionary Anthropology, in Germany). If we can get some really good results- dating, anatomy and biology, it’ll be just so important for learning more about how Diprotodon lived and died.

Digging up Diprotodon

It was around August 2011 that my friend, Ian Sobbe, received a phone call from a local on the Darling Downs: “I’ve found a skull in the dirt- it looks like a Grand Angus bull”, the caller said. Well, Ian, being not only a local farmer from the Downs but also an amateur fossil collector, started to get excited. Knowing a lot about the fossils from the region, Ian checked out the photos that the local had emailed him and immediately called me up. The skull was not a Grand Angus at all, but as Ian correctly identified, it belong to the extinct mega-marsupial, Diprotodon.

The Diprotodon skull was found eroding out of this creek bank

The Diprotodon skull was found eroding out of this creek bank

Diprotodon was a giant among giants- not only the largest marsupial that lived on the Darling Downs during the Pleistocene, but is also the largest marsupial that ever lived… at any time… anywhere on the entire planet! Resembling an oversized long-legged wombat, Diprotodon was truly the king of Ice Age Australia. The cause of its extinction around 40 thousand years ago is heavily debated. The leading hypotheses developed to explain its extinction are centred around climate change associated with the last glacial cycle, or human impacts (such as through overhunting). The debate is one of the most polarised in Australian palaeo-sciences. The difficulty in determining the cause of the extinction of Diprotodon and other megafauna, is in part, due to a lack of reliable data with which to test the leading extinction hypotheses- especially well-dated fossil records. But here, Ian and I saw a great opportunity to travel out to the new fossil site, not only to excavate the new specimen, but to collect some samples critical for dating.

The Diprotodon is over 90cm long!

The Diprotodon is over 90cm long!

Ian and I met with the discoverer and travelled down to the creek where the skull was found eroding out of an ancient deposit. Our jaws dropped when we saw it- it was a monster, measuring around 90 cm in length! With the help of the discoverer, we excavated the skull. During the day, I spent a bit of time documenting the geology of the area, as well as collecting some sediments for optically-stimulated luminescence (OSL) dating. There was also a little bit of charcoal buried in amongst the skull- I also collected it with the plan to date it using radiocarbon methods.

The plaster jacket containing the skull weighed around 170 kg!

The plaster jacket containing the skull weighed around 170 kg!


We put a plaster jacket around the skull to protect it, but it was just so enormous that the three of us were not able to carry it. We were able to lift it with some difficulty- Ian and the local on the back-end, me on the front, but we just couldn’t move it out of the deposit- we sunk right down into the mud and couldn’t move. We ended up going back to the vehicles and drove around the neighbourhood looking for help. We came across some electrical tradies and asked them for assistance- thankfully they said ‘yes’! It took five of us to get the skull up out of the gully, carried across the field, and lifted into the back of Ian’s ute. We estimated that the plaster jacket, with the skull and surrounding sediment, weighed around 170 kg!

Ian is currently in the process of preparing the skull. It’s starting to look pretty good too- one of the best preserved skulls that has ever been discovered, not only on the Darling Downs, but across the entire continent. I’ll be sure to post some pics of the skull when it is finally cleaned up!

Excavating the owl’s dinner plate

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!

Redating the Neds Gully megafauna deposit

Debate over the timing and causes of extinction of Australia’s Pleistocene megafauna has become polarised in part due to a paucity of reliable geochronological information for the extinct forms. Thus, it is difficult to accurately test leading extinction hypotheses in relation to human continental colonisation and climate change events.

The Neds Gully megafauna site on the Darling Downs, southeastern Queensland, has a central role in the extinction debate. Although it is commonly regarded as the continent’s youngest megafauna-bearing deposit (possibly dating to around 40-50 thousand years ago), the provenance of existing dates to the fossils and general stratigraphy of the site has never been formally demonstrated. Thus, the significance of the deposit with respect to the broader extinction debate remains unclear.

So there remains the question: Is Neds Gully really the youngest megafauna fossil site in Australia? Providing the answer to this important question has been the focus of some of my recent work on the Darling Downs.

The Neds Gully fossil deposit was excavated in the 1990’s, long before I was even interested in studying palaeontology. Numerous specimens were collected and accessioned into theQueenslandMuseum. Unfortunately, a comprehensive description of the site was never published. Over the past couple of years, I’ve been revisiting the site to try to determine exactly where the fossils and dating samples were collected from. Fortunately, I have had the help of my friend and colleague, Ian Sobbe. Ian wears a couple of different caps- one as a local farmer, and the other as an amateur palaeontologist. Ian was one of the original excavators of Neds Gully, so finding the site again was no problem.

We reopened the site, bringing in some earth moving equipment to clear overgrowth and sediments that built up over the deposit. We were able to identify the stratigraphic horizon that produces the fossils and even found some new specimens in the process. Armed with some aluminum tubes and a sledge hammer, Ian and I took some new sediment samples for dating. The samples were sent to my colleague, Dr Andrew Murray atAarhusUniversityinDenmark. Andrew is a specialist in optically stimulated luminescence (OSL) dating and was able to produce some new dates for us.

In additional to the OSL dates, I also produced new uranium-thorium (U/Th) dates directly on the fossils using the thermal ionization mass spectrometer (TIMS) at the Radiogenic Isotope Facility (The University of Queensland). The new dates are particularly exciting for us and match perfectly with the OSL dates.

Without giving too much away, the results broadly support the idea that Neds Gully is one of the youngest megafauna deposits inAustralia. However, we have not found evidence for a mass extinction event as commonly as been suggested. I’m currently in the process of writing this work up, with a view to submit it to a scientific journal very soon, so watch this space!