Australia: The Land Where Time Began
For many years dinosaurs were little known in Australia.
Cetiosaurs (whale lizards) are believed to be primitive sauropods. It is uncertain if the group forms a natural family or is instead a mixture of primitive and poorly known dinosaurs.
Rhoetosaurus brownei, Middle Jurassic, from the Injune Creek Beds, Eurombah Creek, Taloona Station, Roma, Queensland.
The fragmentary skeleton consisted of almost complete leg and pelvic bones, about 28 consecutive tail vertebrae, 7 incomplete dorsal vertebrae and rib fragments, and a single partial cervical vertebra. Subsequently a few more bones were recovered from the same site.
This is one of the most complete sauropod skeletons known from Australia. It is estimated to have been about 12-12 m long and about 4 m high at the hip, and a weight of about 20 tonnes has been estimated. Based on the elongate neck vertebrae it is believed it had a relatively long neck. It has several primitive features, and is the earliest known sauropod in the world. It is believed to have been similar to Cetiosaurusi from the Upper Jurassic of Oxfordshire, England. It lacks any specialised features that could relate it to any of the distinctive sauropod families. As there are many hollow cavities in the bones, a weight-saving mechanism in bones, indicates that it is possibly more advanced than other cetiosaurs. It had a short, rapidly tapering stiff tail that had been interpreted as a way of propping the animal up, as with a kangaroo, when it is feeding from high branches. It has sine been suggested that it could possibly have bonne a weapon on its tail, as did some club-tailed sauropods found in China such Shunosauraus.
In this genus a suite of characters of its caudal vertebrae distinguish it from all other sauropods. The anterior vertebrae are amphicoelus with a solid centra and expanded elliptical articulating surfaces, the centra being slightly laterally compressed. Elongated prezygapophyses with vertical articulating surfaces, absent postzygopophyses and a well-developed hyposphene. The neural spines are robust, not elongated, the anterior ones being subrectangular in lateral view, with an oval median process on the posterior margin above the junction with the hyposphene. Anterior chevorns anr massive, not elonagted, not confluent with their vertebral attachment. In the anterior caudals the neural canal is relatively large. The dorsal vertebrae are opisthocoelus with lateral pleurocoels, complex neural arches with bracing laminae, zygopophysial articulations are small and elevated, and extensive intermural cavities.
Indeterminate Indeterminate, Middle Jurassic (Bajocian) Colalura Sandstone, Bringo Cutting near Geraldton, Western Australia. this pecimen is a small caudal vertebrae. It is believed to be from a sauropod, based on the comparison of the specimen, 6.3 cm long by 4.7 cm wide, with other dinosaur caudal vertebrae. It appears most similar to that of Austrosaurus.
Ozraptor subataii, Middle Jurassic (Bajocian) Colalura Sandstone, Bringo Cutting near Geraldton, Western Australia. The specimen is a single bone, the distal end of a tibia (shin bone). The character of the specimen indicated that it was from an agile theropod about 2 m long. The anatomical features of the shin-ankle connection differ from those of any known theropod, suggesting it may represent a line of dinosaur unique to Gondwanan. It was apparently fairly advanced for its age. It is the oldest theropod bone known from Australia.
This genus is distinguished by its high, almost square-shaped, astragalar groove that has a distinct vertical ridge. The tibia, that is 4 cm wide, has a very narrow medial buttress.
Included in the Allosauridae are many carnivorous dinosaurs from the Late Jurassic ot the Late Cretaceous. They are more advanced than the primitive theropods in a number of features. On the bubis is a 'boot' that is longer anteriorly than posteriorly, reduced forearms with 3-fingered hands and a specialised foot with a reduced 5th digit.
Allosaurus sp. Early Cretaceous (Aptian/Albian), in the Strzelecki Group, 100 m east of Eagle's Nest, between Inverloch and Cape Paterson, eastern Victoria.
The specimen eventually was revealed, after preparation, as an almost complete astragalus (ankle bone) of Allosaurus. At about 5-6 m long and about 2m high, the Victotrian allosaurus was smaller, but more robust, than the North American species, A.fragilis, that reached at least 12 m. The known American species were extinct by the end of the Jurassic, so the Victorian Allosaurus was yet another late survivor in Australia. There is also some evidence, in the form of a partially weathered claw, estimated to have been 15 cm long, that at least 1 much larger Allosaurus species also lived in Australia.
During the Jurassic Victoria was situated close to the South Pole. Although the South Pole wasn't ice-covered at the time, it would still have been cold, too cold for what were previously believed to be cold blooded, scale covered dinosaurs. As some evidence has been found elsewhere that at least some dinosaurs were warm-blooded and at least some were covered with feathers or fur, it seems likely that Australian Jurassic dinosaurs were prime candidates for some sort of warm covering.
The astragalus of the Allosauridae is different from that of all other theropods in restriction of the ascending process to the lateral part of the bone, the median process is large compared with the lateral condyl and across the face of the condyl is a lower horizontal groove. In 6 of the main features of the astragalus the Victorian astragalus resembles more closely that of A. fragilis than any other known form - distinct fibular facet, high and medially restricted ascending process, an inflection on the medial margins of the ascending process, the medial condyl is larger than the lateral one, well-defined calcaneal notch, a distinct groove across the condyles. There are also 6 differences that have been noted between astragalus of A. fragilis and the Victorian specimen, concluding that the differences reflect the ligamentous attachment mode between the astragalus and the tibia, the mode of interlocking between the astragalus and the calcaneum is a specialised condition that is seen only in these 2 forms, indicating that the Victorian specimen is a member of the genus Allosaurus.
?Coeluridae - clade Coelurosauria
Major groups of Coelurosauria (UCMP Berkeley)
These were small, lightly built, fast running carnivores. They were previously believed to be primitive theropods but are now thought to be more specialised than the allosaurids, megalosaurids, abelisaurids and ceratosaurs. Included in Coelurosauria are Compsognathus, oviraptorids, ornithomimosaurids, troodontids, elmisaurids, tyrannosaurids, dromaeosaurids. The hands and feet are often less specialised than in later theropods, and the skull is generally slender with large orbits.
A study has found evidence that many coelurosaurs that were believed to be carnivores may actually been herbivores, or possibly omnivores. (7)
Raptor ornitholestiodes, Early Cretaceous, Grimm Creek Formation, Lightning Ridge, New South Wales.
This specimen consisted of a single opalised hand bone. It would probably been about the size of a small adult Allosaurus, about 9 m long. It is believed by some that other theropod bones from Lightning Ridge probably belong to Raptor. It appears to be completely different from other known families from this time, but it relationships are uncertain.
It is characterised by its first metacarpal bone having an elongated posteromedial process. The feature had previously been seen only in Ornitholestes. It differs from Ornitholestes by the first carpal bone being considerably larger, broader relative to length, more robust and the posteromedial process is more prominently developed.
Indeterminate Indeterminate, Early Cretaceous, Maree Formation, Coober Pedy Opal Fields, South Australia
These were long-necked, long-legged, with very large eyes, looking somewhat like an ostrich. They were mostly toothless and probably had a horny beak on the jaws. Based on track-way measurements they are believed to have been the fastest dinosaurs, possibly reaching speeds of 60-100 km/h. These speed estimates have been disputed by some scientists. They are thought to have been at least partially insectivorous, also feeding on small animals and eggs. From what is known of the fossil record, they appear to have been most diverse during the Late Cretaceous of Mongolia and North America.
Timimus hermani, Early Cretaceous, (Albian), Otway Group, coastal exposure Dinosaur Cove, Victoria.
Besides a ornithomimosaur that is possibly from the Late Jurassic of southern Africa, Elaphrosaurus, all other known ornithomimosaurs are from the Late Cretaceous of North America and Asia. The relationship of Elaphrosaurus to ornithomimosaurs has been challenged. Based on the discovery of T. hermani it has been suggested that the ornithomimosaurs arose in Gondwana, only later spreading to Asia and North America.
These theropods are known mainly from the Late Cretaceous of Asia and North America. They had a strange appearance, with unusual lower jaws that had angular and surangular bones with short, toothless dentaries. They are thought to be close to the ancestry of birds, more recently it has been suggested that they are in fact primitive birds.
Based on an early discovery in the Gobi Desert of an oviraptorid near a dinosaur nest with eggs in it, it was believed that it was probably trying to feed on the eggs of Protoceratops when it died. More recent finds suggest that it may have been brooding its own eggs. The discovery of a possible oviraptorosaur in Australia suggests that they may have arisen in Gondwana, spreading to Northern Hemisphere later.
Indeterminate Indeterminate, Early Cretaceous, (Albian), Otway Group, coastal exposure Dinosaur Cove, Victoria.
This species is represented by part of a lower jaw bone. The lower jaw would have measured about 20 cm, suggesting an overall length of about 2 m. The features of the jaw are intermediate between those of dromaeosaurids and oviraptorosaurids. An isolated theropod vertebrae has been tentatively identified as belonging ot the same group.
These wee small to medium sized theropods. They had a well-developed sickle claw on the inner toe of each foot, and their hads had unusually large claws. They are considered by some to be the dinosaur group most closely related to birds. The genera Veloceraptor and Deinonychus belong to this group.
Indeterminate Indeterminate, Early Cretaceous, (Albian), Otway Group, coastal exposure Dinosaur Cove, Victoria.
Walgettosuchus Woodwardi, Early Cretaceous, Grimm Creek Formation, Lightning Ridge, New South Wales.
Indeterminate Indeterminate, Early Cretaceous, Birdrong Sandstone, north of Kalbarri, Western Australia.
Indeterminate Indeterminate, Early Cretaceous, Molecap Greensand, Molecap Quarry, near Gingin, Western Australia.
Indeterminate Indeterminate, Late Cretaceous, Miria Formation, Giralia Range, south of Exmouth Gulf, Western Australia.
Until recently the Titanosauridae were believed to be represented in the Late Cretaceous, now a find in Mongolia dating from the Late Cretaceous has been referred to a new family, the Nemegtosauridae. Titanosaurids had very robust front leg bones. Some Gondwanan forms reached huge sizes that make them amongst the largest known animals to have ever lived.
Austrosaurus mackillopi, Early Cretaceous, Allaru Mudstone (probably also Winton formation), Cluth Station, about 60 km from Maxwelton, West of Townsville, Queensland.
Indeterminate Indeterminate, Early Cretaceous, unknown formation, near Hughenden, Queensland.
The Thyreophorans are the dinosaur group containing armoured stegosaurs, nodosaurs, ankylosaurs and ceratopsians. Ankylosaurids were small to medium sized quadrupedal dinosaurs with bony armour plates in the skin, some also having well-developed spines and tail clubs. The had broad heads, and some grew to massive sizes, e.g., Ankylosaurus reached at least 10 m in length.
Minmi paravertebra, Early Cretaceous, Minmi Member, Bungil Formation, just south of Mack Gulley, north of Roma, south central Queensland.
Minmi sp., Allaru Mudstone & Toolebuc Formation, near Richmond, central Queensland,
?Leptoceratops indeterminate, Early Cretaceous (Aptian), Strzelecki Group, coastal exposures, The Arch, near Inverloch, southeastern Victoria.
This family of dinosaurs filled the niche held by gazelles in the modern world, being mostly small herbivores with high-crowned teeth with numerous ridges for chewing tough plant material.
Leaellynasaura amicographica, Early Cretaceous (Aptian/albian), Otway and Strzelecki Groups, coastal exposures, including Dinosaur Cove, Otway and Strzelecki Ranges, Victoria.
Atlascopcosaurus loadsi, Early Cretaceous (Aptian/albian), Otway and Strzelecki Groups, coastal exposures, including Dinosaur Cove, Otway and Strzelecki Ranges, Victoria.
Fulgurotherium australe, Early Cretaceous, Grimm Creek Formation, Lightning Ridge, New South Wales. Possibly also Otway and Strzelecki Groups, coastal exposures, including Dinosaur Cove, Otway and Strzelecki Ranges, Victoria.
Indeterminate Indeterminate, Early Cretaceous, Grimm Creek Formation, Lightning Ridge, New South Wales.
Muttaburrasaurus langdoni, Early Cretaceous, Mackunda Formation, Thompson River near Muttaburra, Queensland. Also Allaru Mudstone, Dunluce near Hughenden, Queensland & Grimm Creek Formation, Lightning Ridge, New South Wales.
|Author: M.H.Monroe Email: firstname.lastname@example.org Sources & Further reading|