Etymology
Pterosaur – meaning ‘winged lizard’ in Greek.
Currently two pterosaur species that have been named from the Richmond and Hughenden region:
Aussiedraco molnari – The genus name ‘Aussie’ (a shortened form of Australian) and ‘draco’, from Latin meaning dragon. The species name molnari honors Dr Ralph Molnar who made many important contributions to our knowledge of Australian vertebrate fossils.
Mythunga camara – The genus name ‘Mythunga’, referring to a constellation depicting a hunter (from an unspecified western Queensland aboriginal dialect). The species name camara (kamara), from the Greek meaning chamber, referring to the hollow, boxlike structure of the snout.
Relationships
Pterosaurs are close cousins of dinosaurs and crocodiles; belong in the Archosauria which literally translate as ‘ruling reptiles’. Pterosaurs and dinosaurs specifically sit within the Ornithodira, a group charcteristed by moderately large heads with numerous holes in the skull, hollow limb bones and the three middle fingers (digits II–IV) bound together as a functional hand.
The ancestor of all pterosaurs is still uncertain, mainly because they are a highly derived (‘advanced’) animal having specialised features in the skeleton for flight. Hence, pterosaurs look quite different to their nearest relatives, making a comparison of anatomy almost impossible. The earliest true pterosaurs appeared over 228 million years ago in the Late Triassic. They diversifying in both the Jurassic and Early Cretaceous, before declining quickly in the Late Cretaceous. Finally, they went extinct during mass extinct event 65 million years ago along with most marine reptiles and dinosaurs.
All the pterosaurs found in Queensland belong to the Pterodactyloidea. This suborder appeared during the Middle Jurassic, and differ from the more ancestoral “rhamphorhynchoid” pterosaurs by having much shorter tails and longer wing metacarpals (hand bones). Within the Pterodactyloidea the species found around Richmond and Hughenden mostly belong to a subgroup called the Ornithocheirae. These were relatively large pterosaurs (wingspans seven metres) with large, fang-like teeth and a low crest placed at the front of the snout. However, there’s evidence that another group of pterosaurs, the Ctenochasmatoidea, were also present. This is a more ancient group of pterodactyloids which have long, slender snouts and small teeth.
Discoveries
The pterosaur record in Australia is very poor, possibly due to the lack of good rock exposures of the right age on the continent. Known discoveries to date include two bones from Western Australia, several fragmentary bones from Victoria, three tiny fragments from the opal fields of Lightning Ridge in New South Wales and over 20 isolated bones from northern and western Queensland. This is in contrast to the discovery of entire skeletons in some countries around the world. With the exception of one isolated specimen from the Walsh River in far north Queensland, all of the Queensland pterosaur discoveries have come from the Eromanga Basin in the western districts of the State.
Presently there is only a single named species that has been found near Richmond, Mythunga camara – represented by an incomplete skull fragment and partial mandible. Mr Phillip Gilmore found these bones in 1991 on Dunluce Station. Later the material was donated to the Queensland Museum, where Dr Ralph Molnar and Dr Tony Thulborn described it in 2007. Other pterosaur material from the same region was described in 2010 by Dr Tamara Fletcher and Dr Steve Salisbury. It included only fragmentary remains which have been assigned to indeterminate species such as: Ornithocheiridae indet., cf. Anhanguera sp., and Ctenochasmatoidea indet.
Aussiedraco molnari is the other named species of pterosaur in Australia – it’s based on a fragment of lower jaw. It was originally found at an unspecified locality some 13 km South of Hamilton Hotel, about 70 km East of Boulia and mentioned by Dr Tony Thulborn in 1980. At first it was regarded as representing a species closely related to Ornithocheirus. Later it was placed in was questionably assigned to the species Anhanguera? cuvieri, before being placed in the genus Lonchodectes and then back to Ornithocheirus. Finally the specimen was full redescribed and named by Dr Alexander Kellner, Dr Taissa Rodrigues and Dr Fabiana Costa in 2011.
Kronosaurus Korner currently has the remains of two ornithocheirid crests found by Mr Ian Bool and Mr Len Shaw in 2011 at the Free Fossil Hunting Site 1 near Richmond. These specimens are currently being studied by researchers at the Queensland Museum. They may prove to be from a creature very similar to Mythunga camara.
Geology
The pterosaurs from the Early Cretaceous of Queensland are best known from the Late Albian Toolebuc Formation (approximately 100 million years old). However a few scattered remains have also been collected from the younger Mackunda Formation. These units belong to the Rolling Downs Group of Northwest Queensland.
Description
Although they were unrelated, pterosaur had a very bat-like appearance. The wing of pterosaurs comprised of leathery skin stretched under the arm from the tip of the elongate fourth finger (also called digit IV or the ring finger) to the ankle. The fifth finger was lost, and the digits I, II and III were free of the wing in a small hand. The "pteroid" bone, unique to the pterosaur group, attached to the wrist and pointed toward the shoulder, also helped support the wing.
The Ornithocheirae found around Richmond and Hughenden (including Mythunga camara and Aussiedraco molnari) were relatively large pterosaurs, with a wingspan of approximately 4 m in length. They would have had long slender skulls up to 60–70 cm and lined with up to 26 fang-like teeth. At the tip of the snout was a large keel-shaped crest on the upper and lower jaws.
Conversely, the species assigned to the Ctenochasmatoidea would have been much smaller pterosaurs. Although there are no complete examples in Australia, close cousins such as Ctenochasma and Gnathosaurus suggest a wingspan of only 1.5–2 m. These close cousins also have a shorter skull at 28 centimetres long, often with over 100 long needle-like teeth in a flat, spoon-shaped jaw.
Palaeobiology
Pterosaurs in the Richmond region likely lived near the coastline and feed on the abundant fish in the Eromanga Sea. In particular, their fang-like teeth (in species like Mythunga camara) suggests these pterosaurs were well suited for gripping small, slippery prey. Large bony crests on the jaws of some pterosaurs may have also helped them to minimize hydrodynamic resistance as they plucked their victims from the water, like modern Frigatebirds. Like other pterosaurs, the species from Richmond may have had hair-like filaments known as “pycnofibers” cover much of the head and body. The presence of structures suggest that these pterosaurs were endothermic (warm-blooded). Given that flight requires a lot of energy, it seems likely that pterosaurs would have been to warm-blooded to keep such active lifestyle.
ReferencesBennet, C. S. and Long, J. A. 1991. A large pterodactyloid pterosaur from the Late Cretaceous (Maastrichtian) of Western Australia. Records of the Western Australian Museum 15: 435–444.
Fletcher, T. L. and Salisbury, S. W. 2010. New pterosaur fossils from the Early Cretaceous (Albian) of Queensland, Australia. Journal of Vertebrate Paleontology, 30, 1747–1759.
Kellner, A. W., Rodrigues, T. and Costa, F. R. 2011. Short note on a pteranodontoid pterosaur (Pterodactyloidea) from western Queensland, Australia. Anais da Academia Brasileira de Ciências, 83, 301–308.
Molnar, R. E. 1987. A pterosaur pelvis from Western Australia. Alcheringa 11, 87–94.
Molnar, R. E. and Thulborn, R. A. 1980. First pterosaur from Australia. Nature 288, 361–363.
Molnar, R. E. and Thulborn, R. A. 2007. An incomplete pterosaur skull from the Cretaceous of north-central Queensland, Australia. Arquivos so Museo Nacional, Rio de Janeiro, v. 65, No. 4, 461–470.
Molnar, R. E. and Wiffen, J. 1994. A Late Cretaceous polar dinosaur fauna from New Zealand. Cretaceous Research 15, 689–706.