Tag Archives: EXTINCTION

A Crime scene of the past – investigating tropical ice age megafauna

By Rochelle Lawrence, Palaeontological Research Assistant, and Scott Hocknull, Senior Curator, Geosciences, Queensland Museum

In 2008, an extraordinary discovery was made at South Walker Creek, located near the town of Nebo, west of Mackay in Queensland, Australia. Traditional owners of the area, the Barada Barna people, were conducting a cultural heritage survey for the South Walker Creek Mine when they came across some interesting bones. These bones were not the usual white colour, like those of cows you find in the paddock, nor were they light in weight or becoming brittle from exposure to the sun. They were dark coloured, a little heavier than usual and quite solid in form.

We have found the white, brittle bones of modern cows and sheep on many of our fossil surveys. Image Credit: Rochelle Lawrence.
 A fossil osteoderm (bone plate) from the scales along a crocodile’s back and a piece of bone below that was first found at South Walker Creek. Image Credit: Andrea Bull.

The bones were fossils! Fossils are the remains or traces of organisms (animals and plants) from a past geological age. Most fossils form from the bones and hard parts of animals and plants, but sometimes in rare conditions the soft parts, such as flesh and organs, can be preserved. The feathers, fur and stomach contents of animals have also been preserved, as well as small creatures, like insects, trapped in the sticky sap of trees, which has hardened into amber over millions of years. Trace fossils can include animal droppings, burrows, eggs or footprints, which can tell us a lot about the animal’s habits. They are all evidence of once-living things!

Brachiood fossil found at Homevale National Park on 29/09/2008 by Josh Moulds.

Fossils are found all over the world, but they only represent a few of the many organisms that have existed on the planet. Special conditions are required for an organism to become a fossil and survive the changes within the Earth’s sediment through time. Firstly, an organism has to be buried by sediment, such as mud and sand, which is usually washed in by water. The next stage of fossilisation depends on the organism itself and the environmental conditions. The bones from South Walker Creek have undergone a process called (per)mineralisation. Minerals from the soil and water in the creeks enter the cracks and pores of the bone making it harder over time and giving it a stony appearance.

White cards with field numberes were used to indicate the fossil bones found within the ancient creek. The one on the left is an arm bone (humerus) from a giant kangaroo, which has a whole other story – stay tuned with future blogs. Image Credit: Josh Moulds.

The environmental officers of the mine contacted the Queensland Museum where they were put in touch with palaeontologist, Dr. Scott Hocknull, who studies fossils of ancient life. Dr. Scott and his team worked with the traditional owners and mine officers to conduct natural heritage surveys, looking for more fossil remains and traces of past ecosystems within the geological landscape (geology) along the Walker Creek system.

The team surveys the ancient creeks and floodplains of the area looking for other fossil sites. Image Credit: Josh Moulds.

On inspection of the fossils, Dr. Scott identified them belonging to extinct giant creatures, not dinosaurs, but megafauna! The megafauna we refer to here occurred during the ice ages of the Quaternary Period from 129,000 to 11,700 years ago. An exciting find was waiting for them in the form of a partial skull from the giant wombat-like marsupial, Diprotodon optatum.

The tooth rows from a skull of the giant wombat-like marsupial, Diprotodon optatum, were eroding out of the ground. Image Credit: Josh Moulds.

The megafauna fossils from South Walker Creek mostly represent †extinct species, some of which are new to science, along with a few extant (living) species that survive today. We have found predators such as crocodiles †Pallimnarchus (giant freshwater crocodile), † ‘Quinkana’ (terrestrial crocodile) and Crocodylus (saltwater crocodile), the giant goanna †Megalania (Varanus priscus) and the marsupial ‘lion’ †Thylacoleo.

A fossil tooth from a crocodile found while surveying. Image Credit: Josh Moulds.

These predators would have preyed on the herbivores (plant eaters) that they lived with, such as the giant wombat-like marsupial, †Diprotodon optatum, giant wombats like †Phascolonus gigas, the strange giant sloth bear-like marsupial, †Palorchestes, and kangaroos, including the giant forest wallaby, †Protemnodon, a short-faced kangaroo (†Sthenurine), the red kangaroo (Osphranter rufus), a giant wallaby (†Notomacropus) and a giant deer-like kangaroo (†Macropus sp.). 00Rare fossils, including eggshell, of the emu (Dromaius novaehollandiae) have also been found.

Dr. Scott excavates the tooth rows and partial skull of the Diprotodon to carefully remove it from the ground. Image Credit: Josh Moulds.

In among the megafauna bones we also find small fauna of both aquatic (water-dwelling) and terrestrial (land-dwelling) species, along with the fossil impressions of leaves and seeds from the plants that grew in the environment at the time of the megafauna. These delicate remains are rarely preserved in fossil sites of this age and are especially uncommon in the tropics making these sites extra special for palaeontologists. Since 2008, teams have undertaken fieldwork to survey, salvage and excavate fossil sites at South Walker Creek and this work continues today.

Dr. Scott and field volunteer, Noel Sands, carefully carry the partial skull of Diprotodon out of the site as if it were the Ark of the Covenant from Indiana Jones. Image Credit: Josh Moulds.

The fossil discoveries from South Walker Creek are exciting because little is known about the megafauna from the tropical northern regions of Australia compared to those that have been studied in southern Australia. The site is significant as it preserves fossil evidence that is very close to the time of the megafauna’s ultimate extinction in Australia. By studying the site, we are finding answers to our questions surrounding the evolution and extinction of megafauna. Documenting the responses of megafauna to past environmental change is important to better understand the impacts of future change on our living species.

The team celebrate their exciting fossil finds and Diprotodon treasure. Image Credit: Queensland Museum and BHP.

Stay tuned for future blogs on South Walker Creek fossils as we take you behind the scenes and delve deeper into the past of these tropical ice age megafauna.

Project DIG is a partnership between Queensland Museum and BHP that will digitise and scan our collections and research for people worldwide. Check out our Tropical Megafauna in 3D!

Top Image – The main site of the South Walker Creek megafauna fossils where we are excavating their remains within an ancient floodplain. Image Credit: Josh Moulds.

What are megafauna?

By Rochelle Lawrence, Palaeontological Research Assistant, and Scott Hocknull, Senior Curator, Geosciences, Queensland Museum.

Megafauna are giant animals usually weighing over 44 kilograms (kg). Most megafauna are now extinct (no longer exist) and were closely related to living species of animals we see today. You have probably heard of the more commonly known megafauna species, like the saber-toothed cat and woolly mammoth from North America.

Here is a cast of a saber-toothed cat, Smilodon fatalis, from the La Brea Tar Pits in Los Angeles, California, United States of America, that I walk by in our Queensland Museum’s Geosciences collection. Image Credit: Rochelle Lawrence.

However, Australia is unique with its own megafauna ranging from huge and sometimes strange marsupials (mammals with a pouch), like the giant sloth bear-like Palorchestes to very large monitor lizards like the giant goanna, Megalania. There were giant wombat-like marsupials the size of a rhinoceros like Diprotodon, an array of giant kangaroos different to today’s species and a weird super-predator called Thylacoleo, which means pouched-lion. Australia even had giant, armoured tortoises with clubbed tails, land-dwelling crocodiles, giant constricting snakes and huge flightless birds.

Reconstruction of one of my favourite megafauna, Palorchestes. Image Credit: Andrey Atuchin, Rochelle Lawrence, Scott Hocknull © Queensland Museum.

Megafauna can also refer to species that weighed less than 44 kg, but resemble a giant version of a closely related living species. For example, the extinct ‘giant’ koala (Phascolarctos stirtoni) was larger than the living koala (Phascolarctos cinereus) and probably weighed under 15 kg. Others include a giant echidna, (Megalibgwilia), the Thylacine or Tasmanian Tiger and a larger relative of the Tasmanian devil, Sarcophilus laniarius. The term ‘megafauna’ is still used to refer to our largest living animals today such as the elephant.

Can you think of any other living megafauna or extinct?

A species of living megafauna, the elephant, we saw on safari in Namibia, Africa. Image Credit: Rochelle Lawrence.

The megafauna arose well after the extinction of the dinosaurs at the end of the Cretaceous Period, 66 million years ago. In Australia they reached their largest size during the Quaternary Period (2.58 million to 11,700 years ago). The rapidly changing climatic and environmental conditions created grasslands and open habitats favouring the worldwide evolution of gigantic animals. Towards the end of the Quaternary, extinctions of megafauna occurred with nearly two-thirds of Australia’s largest animals dying out, along with many smaller species.

Skeletons of extinct megafauna, including the woolly mammoth, we saw in the Palaeontological Museum of Liaoning in China. Image Credit: Rochelle Lawrence.

There is a great debate in palaeontology (study of ancient life) and archaeology (study of human history) surrounding the big questions of why and how did the megafauna go extinct? Answers revolve around an extended period of severe climate change or human activity, or a combination of both, resulting in extreme changes to the environment. To answer these questions, we have to keep searching for the evidence and investigate more megafauna fossil sites – if they have been lucky enough to be preserved and can be found! Each individual site is a reflection of the different creatures and environmental conditions that existed within the ecosystem of that region representing a small piece of a bigger puzzle involving the whole of Australia and even the world. 

Reconstruction of a Diprotodon who had met its fate. Image Credit: Robert Allen © Queensland Museum.

Climate change here refers to the long-term, natural processes that can change the Earth’s climate such as its orbit around the Sun, changes in solar radiation, levels of greenhouse gases, and plate tectonics (movement of the Earth’s crust). These changes appear locally in the form of sustained changes in weather patterns, like decreases and increases in temperature, the frequency of droughts or flooding and overall intensifying aridity. Human activity during this time refers to hunting and disturbance patterns to the environment such as the burning of the landscape.

The drying and cracking of the earth I captured in outback Queensland. Image Credit: Rochelle Lawrence.

Today climate change includes anthropogenic drivers, like pollution from increased industrial activities of humans. Some of these include the burning of fossil fuels that generate extra greenhouse gases, pollutants and deforestation. These influence how the temperatures across the globe are regulated and drive global warming, a rise in the average temperature of the Earth’s climate system.

Smog from pollutants, such as cars, released into the atmosphere surrounding a bustling city in Asia. Image Credit: Rochelle Lawrence.

Megafauna fossils have been found around Australia and throughout Queensland. Those from the Quaternary Period have been found within sites in southern Queensland like the Darling Downs and Eulo. These sites are well known for the world’s largest wombat-like marsupial, Diprotodon optatum. Diprotodon would have browsed and grazed through the open woodlands and grassy plains of the downs and around the mud springs of Eulo, where on occasion they got stuck, leaving their bones for us to find tens of thousands of years later.

During this excavation we used the numbers to show where the bones of Diprotodon are situated within the ancient mud spring near Eulo. Image Credit: Rochelle Lawrence.

As we head north into the subtropics of central eastern Queensland we find fossils of megafauna from The Caves region near Rockhampton. The fossil remains of these animals that lived around and inside the cave systems have accumulated in cave chamber deposits. These deposits are unique as they record fossil fauna from different environments that transitioned through time from wet rainforests to dry open-arid habitats and then to today’s special vine thicket refugia (habitat supporting refuge). Here we find fossils of the extinct giant tree-kangaroo, Bohra, who is a larger version of today’s living tree-kangaroo species found in Far North Queensland and New Guinea.

Reconstruction of Bohra from the rainforest deposits. Image Credit: Robert Allen © Queensland Museum.
Dig pit in Colosseum Chamber of Capricorn Caves preserving fossils of animals from modern refugia. Image Credit: Rochelle Lawrence.

Even further north in Queensland, west of Mackay, fossils of megafauna are being excavated from sites at South Walker Creek. These fossil deposits are rare because they preserve a tropical megafauna. Not many megafauna fossil sites have been found in northern Australia. Many of the fossil bones have puncture marks made by predatory crocodiles including the extinct giant freshwater crocodile, Pallimnarchus. These crocodiles would have inhabited the billabongs and creeks, hunting at their edge for unaware megafauna that would come to drink.

Reconstruction of Pallimnarchus. Image Credit: Robert Allen © Queensland Museum.

Research into the megafauna is helping us understand their responses to environmental change during the Quaternary Period and hopefully it will answer the many questions surrounding their extinction. If we can track down our past, we can better understand how our present has been shaped by the extinction of the megafauna and hopefully use that knowledge to prepare for the future impacts of environmental change.

Can you think of any impacts to our environments today that affects our living species?

Project DIG is a partnership between Queensland Museum and BHP that will digitise and scan our collections and research for people worldwide. Check out our Tropical Megafauna in 3D!

Top Image – Reconstruction of megafauna from the Darling Downs. Image Credit: Robert Allen © Queensland Museum.