Ozraptor
Encyclopedia
Ozraptor is an abelisauroid theropod dinosaur
from the Middle Jurassic
(Bajocian
) Colalura Sandstone
of Australia
.
In 1967 a group of four twelve-year-old Scotch College
schoolboys found a fossil
at the Bringo Railway Cutting site near Geraldton
, which they showed to Professor Rex Prider of the University of Western Australia
. He had a cast made that he sent to experts of the British Museum of Natural History in London
who thought it likely belonged to an extinct turtle
. Re-evaluation of the bone in the nineties after being prepared out of the rock by John Albert Long and Ralph Molnar
showed that it actually was the shinbone of some sort of theropod.
In 1998 Long and Molnar named and described the type
(and only) species Ozraptor subotaii. The generic name is derived from "Ozzies", the nickname for Australians, and a Latin
raptor, "seizer". The specific name honours a fictional character, the swift-running thief and archer "Subotai" from the movie Conan the Barbarian.
The holotype
, UWA 82469, was found from layers of the Colalura Sandstone Formation, dating to the middle Bajocian, about 170 million years old. It consists of the distal
or lower end of a left tibia
. Together with Rhoetosaurus
, Ozraptor belongs to the oldest known Australian dinosaurs.
The specimen is eight centimetres long and four centimetres wide at the lower end. From this a total length for the shinbone was estimated of about seventeen to twenty centimetres and for the animal as a whole of about two metres. Three diagnostic features were established enabling it to be upheld as a distinct species of dinosaur: the ascending process of the astragalus
had a rectangular shape with a straight upper end; the astragalar facet had a vertical ridge; the medial condyle
was weakly developed.
Only known from one partial leg bone, Ozraptor is difficult to classify. In 1998 the describers could not more precisely determine the classification than a Theropoda
incertae sedis
. In 2004 Thomas Holtz thought it was a member of the Avetheropoda. In 2005 another study, by Oliver Rauhut, suggested that it was indeed a theropod, and more specifically, a member of the Abelisauroidea based on the presence of the distinct vertical median ridge on the astragalar groove. If so, it would be the oldest known abelisauroid.
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Middle Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
(Bajocian
Bajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
) Colalura Sandstone
Colalura Sandstone
The Colalura Sandstone is a Middle Jurassic geologic formation. Dinosaur remains have been recovered from the formation.-Paleofauna:* Ozraptor subotaii - "Distal tibia."* Indeterminate sauropod remains - "caudal vertebra"-See also:...
of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
In 1967 a group of four twelve-year-old Scotch College
Scotch College, Perth
Scotch College , is one of Australia's leading independent schools for boys, situated in Swanbourne, Western Australia, Australia. The school is a member of the Public Schools Association and is now a Uniting Church school, although it was founded in 1897 by the Presbyterian Church of Australia...
schoolboys found a fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
at the Bringo Railway Cutting site near Geraldton
Geraldton, Western Australia
Geraldton is a city and port in Western Australia located north of Perth in the Mid West region. Geraldton has an estimated population at June 2010 of 36,958...
, which they showed to Professor Rex Prider of the University of Western Australia
University of Western Australia
The University of Western Australia was established by an Act of the Western Australian Parliament in February 1911, and began teaching students for the first time in 1913. It is the oldest university in the state of Western Australia and the only university in the state to be a member of the...
. He had a cast made that he sent to experts of the British Museum of Natural History in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
who thought it likely belonged to an extinct turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
. Re-evaluation of the bone in the nineties after being prepared out of the rock by John Albert Long and Ralph Molnar
Ralph Molnar
Ralph E. Molnar is a paleontologist who had been Curator of Mammals at the Queensland Museum and more recently associated with the Museum of Northern Arizona. He is also a research associate at the Texas natural Science Centre. He co-authored descriptions of the dinosaurs Muttaburrasaurus, Kakuru,...
showed that it actually was the shinbone of some sort of theropod.
In 1998 Long and Molnar named and described the type
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
(and only) species Ozraptor subotaii. The generic name is derived from "Ozzies", the nickname for Australians, and a Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
raptor, "seizer". The specific name honours a fictional character, the swift-running thief and archer "Subotai" from the movie Conan the Barbarian.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, UWA 82469, was found from layers of the Colalura Sandstone Formation, dating to the middle Bajocian, about 170 million years old. It consists of the distal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
or lower end of a left tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
. Together with Rhoetosaurus
Rhoetosaurus
Rhoetosaurus , named after Rhoetus, a titan in Greek Mythology, is a genus of sauropod dinosaur from the Jurassic of what is now eastern Australia. Rhoetosaurus is estimated to have been about 12–15 metres long...
, Ozraptor belongs to the oldest known Australian dinosaurs.
The specimen is eight centimetres long and four centimetres wide at the lower end. From this a total length for the shinbone was estimated of about seventeen to twenty centimetres and for the animal as a whole of about two metres. Three diagnostic features were established enabling it to be upheld as a distinct species of dinosaur: the ascending process of the astragalus
Talus bone
-External links:* *...
had a rectangular shape with a straight upper end; the astragalar facet had a vertical ridge; the medial condyle
Condyle
A condyle is the round prominence at the end of a bone, most often part of a joint - an articulation with another bone. It is one of the markings/features of bones, and can refer to:* On the femur, in the knee joint:** Medial condyle** Lateral condyle...
was weakly developed.
Only known from one partial leg bone, Ozraptor is difficult to classify. In 1998 the describers could not more precisely determine the classification than a Theropoda
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
. In 2004 Thomas Holtz thought it was a member of the Avetheropoda. In 2005 another study, by Oliver Rauhut, suggested that it was indeed a theropod, and more specifically, a member of the Abelisauroidea based on the presence of the distinct vertical median ridge on the astragalar groove. If so, it would be the oldest known abelisauroid.