Agrosaurus
Encyclopedia
Agrosaurus is the name given to the remains of what was originally believed to be a Triassic
prosauropod from Australia
. Agrosaurus would thus be the oldest dinosaur
from that country. However, this appears to have been an error, and the material actually appears to come from Thecodontosaurus
or a Thecodontosaurus-like animal from Bristol
, England
. The type species
is Agrosaurus macgillivrayi.
Members of an expedition from the British sloop
HMS Fly
supposedly collected a tibia
, a claw and some other fragments in 1844 from Cape York, Queensland. The original block was purchased by the British Museum of Natural History in 1879, but the remains were not studied until 1891. Harry Govier Seeley in that year named it Agrosaurus macgillivrayi. The block was prepared in the late 1980s. Following the preparation, Ralph Molnar (1991) noticed similarities to the prosauropod Massospondylus
. Galton and Cluver (1976) saw Agrosaurus as close to Anchisaurus
. Vickers-Rich, Rich, McNamara and Milner (1999) equated Agrosaurus and Thecodontosaurus
antiquus, claiming that the British Museum remains were mislabelled. The difficulty in correctly identifying the source of the fossil lies in the fact that the log of the Fly does not record it. The matrix
in which the prosauropod bones were preserved was tested with rocks of similar age in Cape York and Durdham Downs, the latter being beds where Thecodontosaurus remains have been found in the Bristol area of England. The English beds compared most favourably. In fact, as early as 1906 Friedrich von Huene
had described the rock matrix as 'extremely reminiscent of the bone breccia at Durdham Downs near Bristol' and had renamed the species Thecodontosaurus macgillivrayi. Remains of the jaw of a sphenodont identical to Diphyodontosaurus avonis, a lizard-like reptile common to the Bristol Triassic beds have been extracted. This reinterpretation of Agrosaurus as a misidentified British specimen has been accepted in later works.
From the scant remains the living animal would appear to have been about three metres long (10 ft), with a typically prosauropodan appearance: bulky body, long neck, small head and clawed feet. Like other prosauropods, it was probably equally comfortable on all fours as well as on its elongated hind legs. It was herbivorous or may have been an omnivore
.
The name Agrosaurus is now generally considered to be a nomen dubium
or a junior synonym of Thecodontosaurus. If Agrosaurus is not from Australia, which seems most probable, Rhoetosaurus
and Ozraptor
, both from the Bajocian
(Middle Jurassic
) would be the oldest known Australian dinosaurs. Fortunately they are well documented.
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
prosauropod from 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...
. Agrosaurus would thus be the oldest dinosaur
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 that country. However, this appears to have been an error, and the material actually appears to come from Thecodontosaurus
Thecodontosaurus
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....
or a Thecodontosaurus-like animal from Bristol
Bristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. The type species
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...
is Agrosaurus macgillivrayi.
Members of an expedition from the British sloop
Sloop
A sloop is a sail boat with a fore-and-aft rig and a single mast farther forward than the mast of a cutter....
HMS Fly
HMS Fly (1831)
HMS Fly was an 18-gun sloop of the Royal Navy. She was responsible for the exploration and charting of much of Australia's north-east coast and nearby islands. She was converted to a coal hulk in 1855 and broken up in 1903.-Design and construction:...
supposedly collected a 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....
, a claw and some other fragments in 1844 from Cape York, Queensland. The original block was purchased by the British Museum of Natural History in 1879, but the remains were not studied until 1891. Harry Govier Seeley in that year named it Agrosaurus macgillivrayi. The block was prepared in the late 1980s. Following the preparation, Ralph Molnar (1991) noticed similarities to the prosauropod Massospondylus
Massospondylus
Massospondylus and ) is a genus of prosauropod dinosaur from the early Jurassic Period . It was described by Sir Richard Owen in 1854 from remains found in South Africa, and is thus one of the first dinosaurs to have been named...
. Galton and Cluver (1976) saw Agrosaurus as close to Anchisaurus
Anchisaurus
Anchisaurus is a genus of basal sauropodomorph, and was an early herbivorous dinosaur. Until recently it was classed as a member of Prosauropoda. The name comes from the Greek αγχι/agkhi...
. Vickers-Rich, Rich, McNamara and Milner (1999) equated Agrosaurus and Thecodontosaurus
Thecodontosaurus
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....
antiquus, claiming that the British Museum remains were mislabelled. The difficulty in correctly identifying the source of the fossil lies in the fact that the log of the Fly does not record it. The matrix
Matrix (geology)
The matrix or groundmass of rock is the finer grained mass of material in which larger grains, crystals or clasts are embedded.The matrix of an igneous rock consists of finer grained, often microscopic, crystals in which larger crystals are embedded. This porphyritic texture is indicative of...
in which the prosauropod bones were preserved was tested with rocks of similar age in Cape York and Durdham Downs, the latter being beds where Thecodontosaurus remains have been found in the Bristol area of England. The English beds compared most favourably. In fact, as early as 1906 Friedrich von Huene
Friedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
had described the rock matrix as 'extremely reminiscent of the bone breccia at Durdham Downs near Bristol' and had renamed the species Thecodontosaurus macgillivrayi. Remains of the jaw of a sphenodont identical to Diphyodontosaurus avonis, a lizard-like reptile common to the Bristol Triassic beds have been extracted. This reinterpretation of Agrosaurus as a misidentified British specimen has been accepted in later works.
From the scant remains the living animal would appear to have been about three metres long (10 ft), with a typically prosauropodan appearance: bulky body, long neck, small head and clawed feet. Like other prosauropods, it was probably equally comfortable on all fours as well as on its elongated hind legs. It was herbivorous or may have been an omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
.
The name Agrosaurus is now generally considered to be a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
or a junior synonym of Thecodontosaurus. If Agrosaurus is not from Australia, which seems most probable, 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...
and Ozraptor
Ozraptor
Ozraptor is an abelisauroid theropod dinosaur from the Middle Jurassic 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...
, both from the 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....
(Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
) would be the oldest known Australian dinosaurs. Fortunately they are well documented.