Category Archives: Palaeontology

Reconstructing the Kronosaurus

Kronosaurus queenslandicus was the largest predatory reptile to swim the seas of western Queensland 105 million years ago. This icon of the paleontological world is thought to have grown up to 11 metres in length, with around two metres of that dedicated to its unusually large skull, containing a mammoth set of jaws and dozens of enormous teeth.

Recently, an opportunity arose for the Queensland Museum to add to the State Collection with the acquisition of two lower jaw pieces from a large individual Kronosaurus. Although the Kronosaurus is an iconic animal, surprisingly little is known about its biology, with skulls and jaws a relatively rare find.

Kronosaurus queenslandicus was named in 1924 by Queensland Museum palaeontologist and former museum Director, Heber Longman, based on a piece of jawbone that was discovered near Hughenden, in central Queensland. It was named after the Greek Titan Kronos; so horrible that he ate his own children. Kronosaurus is a pliosaur, an extinct short-necked marine reptile. Its powerful jaws – which worked in a similar way to a crocodile’s – contain rows of large conical teeth, the biggest of which are nearly 30 centimetres long. Kronosaurus was a fierce predator – remains of its stomach contents found in central western Queensland indicate that it fed on turtles and other long-necked marine reptiles. Kronosaurus fossils have been found in the sediments deposited by the inland seas and turned to rock, ranging in age from 112-100 Million years, during the Early Cretaceous Period.

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This particular specimen was found by a private collector near Boulia in western Queensland and, through negotiations with Dr Andrew Rozefelds, Head of Geosciences, Queensland Museum, was acquired through generous Queensland Museum Foundation donations directed towards object acquisition. The jaw adds to the Queensland Museum’s collection of Kronosaurus specimens. The acquisition of the specimen will ensure that this important piece of Queensland’s geoheritage is preserved in the State Collection for perpetuity. Importantly, it will also provide an opportunity for both researchers and the broader community to get up close to this fascinating specimen.

But as is the case with most specimens of this nature, the jaw was not in perfect condition, which meant that certain work needed to be done before the object could be properly studied, displayed and stored safely within the collection. The main goal for the Geosciences team was to cradle the pieces of fossil as best possible, whilst demonstrating the aspects of the jaw that were missing, especially its teeth. Senior Technical Officer, Ms Debra Lewis took on this meticulous and detailed work.

To present the jaw in a life-like pose whilst also safeguarding it from damage, Debra began work on a bespoke base that would serve the dual purpose of supporting the specimen whilst allowing it to be displayed. Debra said that creating such a base is a lengthy process due to how customised it needs to be.

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“The base is made of timber but each one contains an individual cradle sculpted from polymer plaster to suit the weight, angle and intricacies of each piece of jaw. The cradle was glued to the timber and filled in with expandable polyurethane foam, which was then sanded off to create the shape of the base’s sides. Over that, two layers of fibreglass were carefully applied to give the structure strength. The final step was a coat of paint in a specially chosen shade that would not detract from the ‘hero’, our Kronosaurus jaw.”

As the teeth and part of the bone were missing, careful work was done to demonstrate this as accurately as possible. The teeth were made using 3-D modelling and printing – technology that Dr Scott Hocknull, Senior Curator, Geosciences, has developed within Queensland Museum and has become a key feature of his research and engagement work.

“In this case, the benefits of this technology served as a huge time saver,” said Scott.

The usual method for producing replicas is creating a plasticine sculpture and using that to make a mould and then cast from it. In this case, the process would need to be repeated for each individual tooth – all 16 of them – which Debra and Scott estimate could have taken a month of work or more. The same result using 3-D modelling and printing took about 36 hours, with most of this made up of printing time rather than manual labour. This is achieved through digitally modelling one tooth, then digitally sculpting a 3-D model of each of the 16 teeth. Using photographs of the original tooth, a 3-D model of it was created, which can then be modified and printed out. Debra then hand painted each tooth in a colour that matched the remaining bone. The final piece of the puzzle was to come up with a way that the teeth could be displayed so that it was obvious to viewers which part was original fossil and which was a reconstruction.

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“Part of the bone was missing, so rather than replicating this on top of the original, we decided to use clear perspex rods to place the teeth at the correct height and show the position of the teeth as they would have been in the jaw,” said Debra.

This was done by gluing each newly made replica tooth to a clear rod and placing it into a small indentation drilled into the matrix (a build-up of rock where the tooth would have sat) so that the rod would fit snugly and can easily be removed and replaced. So where to from here for our “revamped” Kronosaurus jaw?

The Geosciences team hope that the specimen will go on display, possibly within the permanent Lost Creatures exhibition at Queensland Museum, where it can be enjoyed by visitors. It is currently available to researchers and is being studied by a PhD student, who has been 3-D scanning the pieces of the jaw to reconstruct the animal digitally and learn more about its palaeobiology. Of course, a scientist’s work is never truly done – there is always more to learn and new examples of these extinct species to be unearthed, which in turn will bring new opportunities for research and discovery.

“We’ve known about the enigmatic Kronosaurus for a long time – hopefully we can continue to find out more about this icon of the Cretaceous inland sea,” said Scott.