Paleo Profiles: Muttaburrasaurus

A Muttaburrasaurus from Queensland Museum

Australia is not well known for its dinosaurs. When one thinks of palaeontology and Australia we normally think of the megafauna which went extinct within the last ten thousand years. However, Australia has a plethora of dinosaurs from largely the Cretaceous period which shows the variety of dinosaurs which once roamed the world. We'll look at one of them today: Muttaburrasaurus. The Muttaburrasaurus was a herbivorous dinosaur which would have remained very obscure if not for the famous BBC documentary from 1999 Walking with Dinosaurs. 

Discovery and Fossils

Naturally Muttaburra is proud of its famous local

Muttaburrasaurus was discovered in 1963 just outside the town of Muttaburra in Queensland by a grazier (sheep/cattle farmer) called Doug Langdon. It is rare that a dinosaur skeleton has most of the bones through various reasons regarding preservation so it was a surprise that one would be found by accident in Australia. Due to this word spread fast that a dinosaur had been discovered so locals wanting a souvenir went out to take pieces of the fossil. As a result it took until 1981, and a general amnesty for those who took the bones, for the dinosaur to be formally described. This dinosaur was well preserved with it having a nearly complete skull, vertebrae, parts of the pelvis, and parts of the limbs. This doesn't sound well preserved but it is extremely rare to find this amount of bones belonging to one dinosaur - the weather, scavengers and soil can prevent fossilisation never mind leaving it for millions of years. Taking almost twenty years to be described in 1981 Alan Bartholomai and Ralph Molnar would name this dinosaur Muttaburrasaurus langdoni - Muttaburrasaurus with it coming from Muttaburra and langdoni after its discoverer. Since then several other skeletons, or parts of it, have been discovered making it one of the best known dinosaurs from Australia. Most happen to be teeth from Queensland and northern New South Wales and in 1987 a possible second skull, called the 'Dunluce Skull', was found by a fourteen-year old in Queensland. However, to this day the skull offers confusion about what it means as it resembles the first skull, but it also has some differences. The Dunluce Skull is slightly older than the Muttaburra one possibly indicating that as the dinosaur got older the crest on the skull changed; another theory suggests that one could be male and the other female; and a final theory, suggested by Molnar, that it could be a different species of Muttaburrasaurus. Muttaburrasaurus is the genus, not the species. If it turns out that the two skulls are from different species then it would be similar to a difference between a wild horse and a zebra.

Biology

A Muttuburrasaurus in Queensland Museum

What type of dinosaur was Muttaburrasaurus? First off Muttaburrasaurus was in the group Ornithopoda which was an incredibly diverse group of herbivorous dinosaurs which included the Camptosaurids and the very famous duck-billed dinosaurs, or Hadrosaurs like Parasaurolophus. Originally Muttaburrasaurus was assigned into a family called Iguanadontidae which was named after the second dinosaur to ever be described, Iguanodon. As a result Muttaburrasaurus was often recreated to resemble Iguanodon including giving it a thumb spike similar to Iguanodon - these spikes have never been found so they were eventually taken out of reconstructions. However, it was debated and a 2010 paper determined that Muttaburrasaurus was in fact part of a family closely related to iguanodontids called Rhabdodontids. Ornithopods shared several key biological similarities with many being both bipedal and quadrupedal. The forelimb of the Muttaburrasaurus has hands perfect for supporting weight indicating that it would spend large amounts of times on all fours, and the structure of the pelvis adds to this. Similar to Iguanodon it had a long tail held stiff by strong tendons to act as a counterbalance essential for bipedalism. However, this was noted when it was believed that Muttaburrasaurus was an iguanodontid; Iguanodon was capable of bipedalism and quadrupedalism. The Rhabdodontids were more quadrupedal than bipedal, with some incapable of bipedalism, so Muttaburrasaurus was likely more bipedal than quadrupedal. We also have a question of was it warm-blooded and did it have feathers? The debate about both is skill going on. In 2014 a paper by John Grady and other palaeontologists suggested that non-avian dinosaurs were mesothermic - neither warm or cold-blooded. The debate still rages on, however, and at times gears more towards mesothermy while at other times endothermy. Protofeathers have been discovered on primitive Ornithiscians, (the order containing Ornithopods and other groups including stegosaurids and ceratopsians like Triceratops), called Tianyulang and Kulindadromeus. These were not feathers as you see on a modern bird but more like filaments and fuzz. As a result, more and more palaeontologists are believing that all dinosaurs could have some level of filaments mixed with scales. If you find this hard to believe remember that elephants, rhinos and whales all have hair. We can imagine that Muttaburrasaurus may also have had some form of filaments on its body.

The Muttaburrasaurus with its unique crest

Muttaburrasaurus was a medium sized herbivore reaching around 7 metres, or just under 23 foot, in length and being about 2 metres, or six and a half feet, tall. The most interesting thing about Muttaburrasaurus is its skull. Rising from the front of the snout is a large, hollow nasal crest. One theory has it that it was a large cavity for smell; something useful to smell out potential predators. However, the more recognised theory, and the one shown in Walking with Dinosaurs, that this crest acted as a resonating chamber allowing it to make various unique calls that can be heard over a wide area. The calls could indicate an approaching predator, to a greeting, to possible mating calls. Furthermore, the crest potentially could have been brightly coloured if used for communication - individuals could have different colouring or it could help attract a potential mate. As tissue very rarely preserves it is difficult to know. The two skulls we have have slightly differently shaped crests indicating that it could be differently aged animals, sexes, or species. Finally, we have the teeth. Cretaceous ornithopods normally had teeth adapted to grinding plant matter, and the later hadrosaurs evolved the ability to chew, but Muttaburrasaurus had different teeth. The teeth of Muttaburrasaurus were adapted to sheering and the dinosaur was unlikely able to chew. Molnar originally hypothesised that Muttaburrasaurus was partially omnivorous relying heavily on scavenging. In the 1990s Molnar would re-evaluate the scavenging hypothesis instead noticing the similarities to the ceratopsians, like Triceratops. Ceratopsians had teeth adapted to sheering tough vegetation, mainly cycads, so Muttaburrasaurus could be an example of convergent evolution - like ceratopsians it needed to sheer through hard foliage so evolved teeth and jaws to do exactly that.

When and Where

Cretaceous Australia

As mentioned earlier Muttaburrasaurus was from the Cretaceous; all the Australian dinosaurs that we know of come from either the Jurassic or Cretaceous. The Cretaceous was the last period in which non-avian dinosaurs existed in lasting from 145 million years ago to 66 million years ago. Muttaburrasaurus existed in the Albian and early Cenomanian of the Cretaceous which was near the start of the period with it existing from 112 until 99 million years ago. The Australia which Muttuburrasaurus existed in was very different to the Australia of today. Australia was drifting apart from the continent of Gondwana and up to 50% of today's Australia was covered in shallow seas. This potentially could explain why the Muttaburrasaur fossils we have are well preserved. Plant fossils indicate that Australia was covered in ferns and conifers, all hard foliage indicating Muttaburrasaurus's sheering teeth. Part of southern Australia was attached to Antarctica and was slowly splitting off forming a large rift valley and was in the polar regions. Was Muttaburrasaurus a polar dinosaur? The answer is possibly no. Southeast Australia was in the polar regions and Muttaburrasaurus so far has only been found in the north. Furthermore, Muttaburrusaurus has been found in formations near formations, geographically and in age, where sauropods (long-necked dinosaurs) are found. This is important as sauropods favoured warmer climates. Therefore, we can imagine that at least some parts of the year Muttaburrasaurus lived in a warm climate. Due to the Australia's proximity to Antarctica and an inland sea the climate would not be too warm - Muttaburrasaurus lived in a climate not too dissimilar to Central Europe or New Zealand today, warm in the summer and cold in the winter. Quite possibly to keep warm in the colder periods Muttaburrasaurus had thicker filaments on their bodies. By the Late Cretaceous the inland sea started to vanish and temperatures changed which likely led to its extinction.

Neighbours

Walking with Dinosaurs had Muttaburrasaurus and Leaellynasaura co-existing 

With a habitat that was not too warm or too cool the Muttaburrasaurus had several notable neighbours. The ferns and conifers of Cretaceous Australia had the newly evolved flowering plants growing alongside them allowing for a wide range of dinosaurs to feed off of them. Muttaburrasaurus fossils have not explicitly been found next to other dinosaurs but based on where they have been found and the time they lived we can make guesses. Among them include the ankylosaurid Kunbarrasaurus and various sauropods including Wintonotitan. Pterosaurs flying between the various seas and looking over the rivers would have been a common sight. We know of a few carnivorous dinosaurs from Australia, such as the Australovenator which existed four million years after Muttaburrasaurus went extinct, so we can imagine that some form of carnivore hunted Muttaburrasaurus. Walking with Dinosaurs portrayed them as being migratory existing in the polar regions during the summer and moving north during the winter; this is not too far-fetched but we will have to wait to see if more are unearthed. If future ones are found exclusively in the north we'll know that they didn't migrate and only existed in warmer climates. Only time will tell.

Thank you for reading. The sources I have used are as follows:

-'Muttaburrasaurus', Prehistoric-Wildlife.com, (Accessed 30/08/2018)

-'Australia in the Cretaceous', Western Australian Museum, (Accessed 30/08/2018)

-A. Bartholomai and R.E. Molnar, 'Muttaburrasaurus: a new Iguanodontid (Ornithischia: Ornithopod) dinosaur from the Lower Cretaceous Queensland', Memoirs of the Queensland Museum, (1981), 20:2, 319-349

-Andrew T. McDonald , James I. Kirkland, Donald D. DeBlieux, Scott K. Madsen, Jennifer Cavin, Andrew R. C. Milner, and Lukas Panzarin, 'New Basal Iguanodonts from the Cedar Mountain Formation of Utah and the Evolution of Thumb-Spiked Dinosaurs', PLoS ONE, (2010), 20:2

-Andrew T. McDonald, 'Phylogeny of Basal Iguanodonts (Dinosauria: Ornithischia): An Update', PLoS ONE, (2012), 7:5

-John M. Grady, Brian J. Enquist, Eva Dettweiler-Robinson, Natalie A. Wright, and Felisa A. Smith, 'Evidence for Mesothermy in Dinosaurs', Science, (2014), 344:6189, 1268-1272

-Walking with Dinosaurs, (1999), BBC, 1 November

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