Tag Archives: fossils

Discovering the world’s largest kangaroo- Part 1: In the field

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

As the weather begins to cool, the ‘dig’ season starts for us (palaeontologists) as we venture off along the coast and into the outback heart of Queensland. Over the last ten years we have been investigating a series of fossil sites at South Walker Creek located near the town of Nebo, west of Mackay. It is here that we are finding some of Australia’s last tropical ice age megafauna.

The dig team excavate megafauna bones at the main fossil site on an ancient floodplain. Image Credit: Rochelle Lawrence.

Our dig team usually consists of palaeontologists, along with other scientists and specialists who contribute and volunteer their time. During the year of 2016 one of our volunteers, Noel Sands, who specializes in caving (and their fossil deposits!) called speleology, found a very large fossilized bone. Using an array of brushes and dig tools, Noel carefully excavated the sediment from around the bone to expose its shape and size. It was identified as a tibia (shinbone) [Sketchfab 1] from a kangaroo, but not just any kangaroo, the world’s largest species of kangaroo!

Using a palaeontologist’s tool kit to remove the sediment and find the extent of the bone. Image Credit: Rochelle Lawrence.

Once the position of the bone was established, we trenched around the specimen to create a pedestal so it could be isolated, with its surrounding sediment, from the rest of the dig site. The bone was then recorded and photographed in situ (the original place of deposition). We also place a temporary paddle pop stick [Sketchfab 6, 7)] with an identifying field number on the bone so it can be plotted in 3-D using a process called photogrammetry.

Scott and Rochelle doing the ‘photogrammetry shuffle’ where they take overlapping photos at different heights and angles of the exposed bones across the entire dig site. These photos are uploaded to special software to reconstruct them in 3-D, kind of like a 3-D puzzle. Image Credit: Clare O’Bryen.

To begin the process of extraction, we first cover the bone and pedestal with foil to act as a protective layer. It is then covered with strips of wet newspaper, which provides cushioning for the jacket we are going to make to contain the bone. To make the jacket we use strips of hessian dipped in a plaster mix (casting plaster and water) and wrap them around the pedestal with the bone and wait for it dry. This is always the fun job!

The large tibia bone on the pedestal ready to be jacketed.
Scott, Christina and Natalia have fun plastering the specimen. Images Credit: Rochelle Lawrence.

Once the plaster jacket is dry, the field number and a directional north arrow are written on it so we know which specimen it is and its position in the site. The next step of the process is always tricky and is about getting it just right to roll the jacket over with the specimen kept in one piece. We use a hammer to bang in chisels at the base of the pedestal to loosen it from the underlying sediment. When it becomes loose it is ready to be quickly rolled over. If we have made a good jacket the specimen should stay all in one piece. On rare occasions we are not so lucky, but this time it went without a hitch! You can see this whole process in the video below, check it out!

Scott using a hammer and chisel to slowly wedge the plaster jacket away from the ground.
Noel and Scott sit happy and proud with the successful roll over of the plaster jacket. Images Credit: Rochelle Lawrence.

Finally, the other side of the plaster jacket is sealed with the same plastering process to form a lid. Now the specimen is protected in a hard, egg-like shell to be transported back to the Queensland Museum and stored temporarily in the Geosciences collection with other unprocessed specimens awaiting preparation. There was also a distal tibia epiphyses (end cap) bone [Sketchfab 3] sitting on the shaft of the tibia and a bone shard [Sketchfab 4] nearby that were carefully collected so they were out of the way of extracting the tibia. We will be able to see if these bones are associated (connected) to the tibia.

Scott and Christina make the lid to the plaster jacket so it is sealed and protecting the specimen inside on its travels back to the museum. Image Credit: Rochelle Lawrence.

Another challenge of the fieldwork is getting large jackets from the dig site back to the field vehicle. As the terrain is quite rough and our excavations occur in an eroded creek bed we cannot drive very close to the dig site. We have to use trollies, stretchers and manual handling to slowly walk the jackets with their specimens out of the dig site. Whilst excavating fossils by hand is exciting, it is also a lot of hard work. It involves good fitness, experience, precision, problem solving and most importantly team work.

Scott and Peter are tasked with transporting the large plaster jacket across the bumpy terrain to the field vehicle using a trolley. Image Credit: Rochelle Lawrence.

Check out Part 2: In the Lab as we go behind the scenes to investigate the giant kangaroo leg further.

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 dig team sit proudly around the tibia of the world’s largest species of kangaroo, all ready to be extracted. Image Credit: Rochelle Lawrence.

 

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.