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A Dinosaur with an ID Crisis

The skeleton of Kunbarrasaurus ieversi

The skeleton of Kunbarrasaurus ieversi, Australia’s most complete dinosaur fossil. Photograph © A. O’Toole & L. Leahey

By Lucy Leahey

It’s little wonder that a dinosaur with a parrot-like beak, bones in its skin and an inner ear like a turtle confused the palaeontologists who discovered it in Queensland in 1990.

Most people dream about discovering ancient relics or dinosaurs in their backyard. This became a reality for the Ievers family in 1989 when they stumbled across a 100 million-year-old, near-perfectly preserved pliosaur (a marine reptile with flippers) in the paddock behind Marathon Station’s homestead near Richmond in north-west Queensland.

So it wasn’t too much of a surprise when a couple of months later they came across what they thought was another marine monster. They immediately contacted the Queensland Museum, and a very excited group of palaeontologists made the trek out from Brisbane in the scorching summer heat of January 1990.

Dr Ralph Molnar, who was the Museum’s curator, led the dig. He soon realised that this skeleton wasn’t from an animal that had lived in the Eromanga Sea – an ancient sea that had extended over the interior of Queensland – but that of an ankylosaur that had been washed out from the nearby land.

Ankylosaurs are often referred to as the “armoured tanks” of dinosaurs. They were herbivorous, rotund creatures with four stout legs, but their most unique feature was that they were covered in a diverse array of dermal armour similar to what we see in crocodiles today. While this armour would have included ossicles (small pebble-shaped bones), plates and spikes, they are most famous for possessing tail-clubs. They existed throughout the world approximately 170–65 million years ago and are closely related to the stegosaurs.

Upon their return to Brisbane, the Queensland Museum began work on the Ievers’ ankylosaur immediately. It turned out that in the modern world this was to become not only Australia’s most complete dinosaur skeleton but also one of the world’s best-preserved ankylosaurs. Approximately 95% of the skeleton is preserved, along with fossilised skin and the remains of the animal’s last meal.

Despite its scientific and geocultural significance, Molnar was only able to publish a partial description of the Ievers’ ankylosaur before retiring in the late 1990s. Molnar grouped it with Minmi paravertebra, the only other ankylosaur then known in Australia from fragmented remains discovered near Roma, Queensland. And there it remained for the next 15 years.

Minmi Gets a Makeover

Under the tutorage of Molnar and Dr Steve Salisbury of The University of Queensland, I began my work on the Ievers’ ankylosaur in 2007. This involved the description and interpretation of the skull bones as well as CT scanning at the Mater Adult Hospital in Brisbane.

Our investigations revealed that the Richmond ankylosaur discovered by the Ievers family was significantly distinct from the Roma specimen of Minmi paravertebra, as well as from all other known ankylosaurs, so we decided it warranted a new name. Thus Kunbarrasaurus ieversi was born. The word “Kunbarra” (pronounced koon-ba-rah) means “shield” in the Mayi language of the Wunumara people from the Richmond area, while the species name honours its discoverer Mr Ian Ievers, thus meaning “Ievers’ shield lizard”.

Kunbarrasaurus vs the World

Ankylosaurs are known for their armour, which not only occurs on the body but also extends onto the skull. In the majority of ankylosaur skeletons so far described, this amazing feature is so extensive that the individual bones of the skull are obscured from view so that the skull appears to be formed from a single bone. Therefore little is known about the configuration of the bones of the ankylosaur skull and its evolution.

Only four ankylosaur skulls exhibit sutures (junctions between the skull bones) that enable the shape of the skull bones to be examined. Kunbarrasaurus is one of these ankylosaurs. Of the three remaining ankylosaur skulls one belongs to Cedarpelta from North America, and the other two are juvenile specimens of a very advanced form of ankylosaur from Mongolia called Pinacosaurus.

Cedarpelta and Kunbarrasaurus were both found in Lower Cretaceous rocks approximately 100 million years old. This is a time in the early evolution of ankylosaurs from which little is known. The majority of our knowledge on the early evolution of the group comes from isolated and fragmentary specimens.

Despite this, current evidence suggests that the group was beginning to diversify around this time. Although Cedarpelta is contemporaneous with Kunbarrasaurus, it exhibits more advanced ankylosaurian characteristics. On the other hand, Kunbarrasaurus displays many features that are considered primitive to the group as they are shared with its last common ancestor, basal thyreophorans such as Scelidosaurus, and possibly more so than any other known ankylosaur. It is thus an ideal specimen in which to study the evolutionary transition between ankylosaurs and their immediate ancestors.

The evolution of some key ankylosaurian features of the skull have up until know been intelligently inferred. These features include the loss of sutures and the occurrence of ornamentation on the skull, as well as closure of fenestrae and foramina (openings in the skull that typically accommodate muscles, blood vessels and nerves).

From comparisons with other ankylosaurs the development of these features can be clearly seen in Kunbarrasaurus. For example, the loss of sutures via fusion occurs from the back of the skull and moves towards the snout. And the origin of ornamentation on the skull is formed through two different methods: armour fusing to the skull bones along with remodelling of the surface of individual skull bones. The closure of fenestrae and foramina is due to the enlargement of bones, and not by them being covered in armour.

Another interesting feature of Kunbarrasaurus is the evidence of a parrot-like beak. Small foramina bountifully dot the bone surface along its jaw. These foramina are also observed along the jaws of modern-day birds and turtles.

From observations of these modern creatures we know that these foramina allow vessels to travel through bone, delivering blood to the beak. Beaks are constantly being ground down as a result of foraging, grabbing and grinding food, and thus – similar to fingernails – they need be continually nourished and grown.

Evidence of beaks is relatively common among most herbivorous dinosaurs. Direct evidence in ankylosaurs, however, is not so common, most likely due to the enormous amount of bone remodelling on the skull.

Inner Headspace

The CT scanning and 3D reconstruction of Kunbarrasaurus raised just as many questions as answers. Initially, despite its extraordinary preservation, the internal structures of the skull were difficult to interpret due to minerals in the rock – most likely calcite, which has a similar density to fossil bone – that still occupy the internal spaces of the skull. Once this was overcome the inner workings of its headspace could be reconstructed.

The features found within the nasal cavity space of Kunbarrasaurus resulted in two potential scenarios to describe its airways. The first was a simple arch from the nostrils to the throat, while the second involved a passage with a single loop.

So far only two other ankylosaur skulls have undergone a similar analysis. Euoplocephalus and Edmontonia are highly advanced ankylosaurs, and both have highly convoluted, multi-looping nasal passages unlike anything seen in other dinosaurs. Thus the airways of Kunbarrasaurus are comparatively more complicated than other dinosaurs but less so than other ankylosaurs.

The North American ankylosaur’s rollercoaster-like airways are thought to have evolved to help control the temperature of the brain. These ankylosaurs sported very heavy armour and would have struggled to keep cool. Their uniquely-shaped airways would also have helped to retain water and may also have been used to create loud bellows. Kunbarrasaurus wasn’t as heavily armoured as other ankylosaurs, and thus may not have needed such a highly elaborate air-conditioning system.

The inner ear of Kunbarrasaurus is extremely large relative to the size of the skull, as well as with other ankylosaurs. Its shape is unlike that of any dinosaur yet known and is more similar to that of a turtle or tuatara. The curious array of structures observed for Kunbarrasaurus – a spherical shape, short semi-circular canals and unossified portions of the cochlear region – suggest possible functions that are incomprehensible at the moment.

The brain of Kunbarrasaurus is similar to other ankylosaurs but does exhibit some unique differences. The ratio of its brain size to the total skull length is almost double that of other ankylosaurs and, like the inner ear, some of the bones surrounding the cavity aren’t fully ossified. Compared with other ankylosaurs, Kunbarrasaurus’ brain shape is primitive but does have some more advanced features, such as the angle of the pituitary gland, which controls development and the endocrine system. The function of these features is yet to be fully examined.

The Next Chapter

The assignment of a new genus and species, Kunbarrasaurus ieversi, to the ankylosaur formerly known as Minmi sp. was based on many significant differences that distinguish it from other ankylosaurs. This study has not only provided an identity for one of Australia’s geotreasures but we’ve also been able to confirm long-held uncertainties about unique ankylosaur features – and raised new questions.

As part of my PhD, I’ve been working to uncover the details of Kunbarrasaurus and other ankylosaur fossils from Queensland. The next phase of the project will be to investigate the rest of the skeleton of Kunbarrasaurus and compare it with the other Queensland ankylosaurs as well as those from around the world.

For Australia, ankylosaurs are one of the most abundant forms of dinosaurs we have evidence for, but unfortunately they have remained mostly unstudied. Interestingly, however, on other continents they form a small percentage of the known dinosaur fauna.

Thus the Australian ankylosaurs are a key group in understanding the overall diversity of the group throughout the world, but particularly within Gondwana. They may also, as has been shown with Kunbarrasaurus, provide crucial insights into the evolution of the group.


Lucy Leahey is a PhD candidate at The University of Queensland’s Vertebrate Palaeontology & Biomechanics Lab. Kunbarrasaurus ieversi is on display at the Queensland Museum in Brisbane. The original research article is available at https://peerj.com/articles/1475