Elliot and Mary fact files

Classification

Order Dinosauria, Suborder Saurischia, Infraorder Sauropoda, Family incertae sedis

Elliot and Mary are sauropod dinosaurs. Sauropods were gigantic four-legged plant-eaters, characterised by long necks and tails, pillar-like legs, and disproportionately small heads. Even the smallest sauropods, which were about 8 metres long and weighed almost 10 tonnes, were larger than most other dinosaurs. Some of the larger sauropods, such as Argentinosaurus and Paralititan, are thought to have exceeded 30 metres in length and weighed as much as 80?90 tonnes, making them the largest animals ever to have walked the Earth.

At present it is unclear exactly what type of sauropod Elliot and Mary represent. All the previous sauropod fossils found in the Winton Formation are thought to belong to a type of dinosaur named Austrosaurus. The first specimen of Austrosaurus was discovered on ?Clutha' Station, 60 km north-west of Maxwelton in the late 1920s. This specimen comprised portions of at least nine enormous vertebrae, embedded in several large blocks of pale grey mudstone. This specimen was described by Heber Longman in 1933 as a distinct species - Austrosaurus mckillopi. Portions of five additional sauropod skeletons were collected from three different localities around Winton in the late 1950s and early 1970s. The first was collected by Dr Alan Bartholomai, a former Director of the Queensland Museum, and the others by Dr Mary Wade. These specimens were described in 1981 by Dr Walter Coombs and Dr Ralph Molnar. Coombs and Molnar were hesitant to refer this material to Austrosaurus mckillopi, but considered it similar enough to the material described by Longman to place it in Austrosaurus sp.

In the past it has been suggested that Austrosaurus belongs to either Cetiosauridae, Brachiosauridae or Titanosauridae, although none of these assignments seems satisfactory. In 2000, Dr Ralph Molnar (Museum of Northern Arizona) reassessed the taxonomic affinities of some of the material referred to Austrosaurus. Although he thought that some of the material previously assigned to Austrosaurus showed clear affinities with tinanosauriform sauropods, the remainder is too fragmentary to confidently refer it to any known sauropod group. Together with Dr Salisbury, Dr Molnar is continuing to review this material, and the results of their research should be available soon. 

Based on the parts of their skeletons that have been found so far, it's very likely that both Elliot and Mary can be referred to Austrosaurus. The alternative is that they may belong to a new genus that was very similar to Austrosaurus. At present, it is unclear whether they belong to the same species, but it seems probably. These questions can only be answered when more material has been collected and fully prepared and studied. 

Other Australian sauropods of similar age

Fossils of other Australian sauropods of a similar age to Elliot, Mary and the other Winton sauropods are few and far between. Isolated teeth are known from Lightning Ridge, and an isolated tail vertebra has been found in the Geraldton region of Western Australia. In the mid 1980s, part of a neck vertebra was discovered near Hughenden, a couple of hundred kilometres north-east of Winton. The Hughenden neck vertebra is thought to belong to a Brachiosaurus-like animal, initially estimated to have been around 20 metres long. But after having seen the mounted skeleton of Brachiosaurus in the Berlin Museum, Dr Salisbury thinks it was much smaller ? probably around 14-16 m. A review of this material is currently being undertaken by Dr Salisbury and Dr Molnar.

Size

The length of his thighbone indicates that Elliot was somewhere between 16 and 21 metres long, 3.5-4 metres high at the rump and weighed approximately 22-28 tonnes (equivalent to five African elephants!). Mary was much smaller, being about half the size of Elliot. Bones that can be confidently referred to her ? a tibia, radius and several thoracic vertebrae ? indicate she was probably about 10-12 metres long and might have weighed about 14-16 tonnes. 

We've known for more than a decade that Australia was home to sauropods as large as Elliot, but until now there have been no bones to prove it. Between 1987 and 1993, enormous sauropod footprints were discovered on the wave-washed rock platforms around Broome, Western Australia. Most of the Broome sauropod footprints are 45-90 cm wide, but at least one set of tracks belongs to an animal with feet an incredible 1.5 m wide ? wider than the diameter of the tyres on most semi-trailers! Footprints this size can only have been produced by a truly gigantic animal, whose size may well have surpassed even that of the mighty Argentinosaurus and Paralititan. Work on the Broome trackways is currently being undertaken by Dr Tony Thulborn.

Age

Elliot and Mary's bones were found in 98-95 million-year-old rocks from the Lower Cretaceous (latest Albian-earliest Cenomanian) Winton Formation. This rock unit blankets large areas of central-western Queensland, and consists of sedimentary rocks such as sandstone, siltstone and claystone. The sediments that make up these rocks represent the remnants of the inland sea that covered large parts of Queensland and central Australia 98-95 million years ago. Great meandering rivers, forest pools and swamps, creeks, lakes and coastal estuaries all left behind a different type of sediment.

In some areas, the Winton Formation is over 400 metres thick. To bring with them such a huge amount of sediment, the rivers that flowed across these plains must have been comparable in size to the present day Amazon or Mississippi. As more and more sediment was brought in, the margins of the inland sea slowly contracted. By around 95 million years ago, the job was complete and the inland sea would never to be seen again.

Relavent scientific references

Coombs, W. P., Jr., & R. E. Molnar, 1981. Sauropoda (Reptilia, Saurischia) from the Cretaceous of Queensland. Memoirs of the Queensland Museum, 20:351-373.

Dettmann, M. E., R. E. Molnar, J. G. Douglas, D. Burger, C. Fielding, H. T. Clifford, J. Francis, P. Jell, T. Rich, M. Wade, P. V. Rich, N. Pledge, A. Kemp and A. Rozefelds, 1992. Australian Cretaceous terrestrial faunas and floras: biostratigraphic and biogeographic implications. Cretaceous Research,13:207-262.

Long, J. A. 1992. First dinosaur bones from Western Australia. The Beagle, Records of the Northern Territory Museum of Arts and Sciences, 9 (1), 21-28.

Longman, H. A. 1926. A giant dinosaur from Durham Downs, Queensland. Memoirs of the Queensland Museum, 8 183-194.

Longman, H. A. 1927. The giant dinosaur: Rhoetosaurus brownei. Memoirs of the Queensland Museum, 8 183-194. 

Longman, H. A., 1933. A new dinosaur from the Queensland Cretaceous. Memoirs of the Queensland Museum, 10:131-144. 

Molnar, R. E., 1991. Fossil reptiles in Australia. In, P. Vickers-Rich, J. M. Monaghan, R. F. Baird, T. H. Rich, E. M. Thompson & C. Williams, eds., Vertebrate Palaeontology of Australasia, (Pioneer Design Studio & Monash University Publications Committee: Melbourne) pp. 605-702.

Molnar, R. E., 2000. A reassessment of the phylogenetic position of Cretaceous sauropod dinosaurs from Queensland, Australia. In, H. A. Leanza, ed., VII International Symposium on Mesozoic Terrestrial Ecosystems, Asociacion Paleontologica Argentina Publicacion Especial, 7:139-144.

Molnar, R.E. & Salisbury, S.W. 2005. Observations on Cretaceous sauropods from Australia. 454-465 In Carpenter, K. & Tidwell, V. (eds). Thunder-Lizards: the sauropodomorph dinosaurs. Indiana University Press, Bloomingon, Indiana. 

Salisbury, S. W. 2002a. A giant awakes. Australian Geographic, 65: 100-105.

Salisbury, S., 2002b. Clash of the titans. Nature Australia, 27, 7:44-51.

Thulborn, R. A., T. Hamley & P. Foulkes. 1994. Preliminary report on sauropod dinosaur tracks in the Broome Sandstone (Lower Cretaceous) of Western Australia. Gaia, 10:85-94.

Thulborn, R. A., & M. Wade, 1984. Dinosaur trackways in the Winton Formation (mid-Cretaceous) of Queensland. Memoirs of the Queensland Museum, 21:413-517.