Austroraptor
Encyclopedia
Austroraptor was a genus of dromaeosaurid dinosaur
that lived about 70 million years ago during the Cretaceous period in what is now modern Argentina
. The type species
for the genus
, Austroraptor cabazai, was described in late 2008 by Fernando Novas of the Museo Argentino de Ciencias Naturales. The fossil specimen was discovered in the Late Cretaceous
deposits located in the Río Negro Province
of Argentina. The species was named in honor of Alberto Cabaza, who founded the Museo Municipal de Lamarque where the specimen was partially studied.
. Particularly notable about the taxon
were its relatively short forearms, much shorter in proportion compared to those of other members of its family. The relative length of its arms has caused Austroraptor to be compared to another, more famous short-armed dinosaur, Tyrannosaurus
.
The type specimen, labeled MML-195, consisted of a fragmentary skeleton including parts of the dinosaur's skull, a few neck and torso vertebrae, some ribs, a humerus, and assorted bones from both legs. The remains were found among deposits of the Allen Formation
of Argentina, dating from the Campanian
to the Maastrichtian
stages of the Late Cretaceous
period 70 million years ago. However little of the entire skeleton was found, what bones were available for analysis expressed some distinct characteristics that differentiate Austroraptor from other dromaeosaurs. A. cabazais 80 centimeter-long skull was low and elongated, much more so than that of other dromaeosaurs. Several of its skull bones bore some resemblance to that of the smaller troodontid deinonychosaurs
. The front limbs of this taxon were short for a dromaeosaur, with its humerus
less than half the length of its femur
. Austroraptor had conical, non-serrated teeth, which Novas et al. compared to those of spinosaurids
.
of the Dromaeosauridae
. Some of these characteristics include the geometry and formation of the specimen's vertebral elements. It was determined that Austroraptor was a close relative of the unenlagiine dromaeosaur Buitreraptor
.
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...
that lived about 70 million years ago during the Cretaceous period in what is now modern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. 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...
for the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, Austroraptor cabazai, was described in late 2008 by Fernando Novas of the Museo Argentino de Ciencias Naturales. The fossil specimen was discovered in the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
deposits located in the Río Negro Province
Río Negro Province
Río Negro is a province of Argentina, located at the northern edge of Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean.Its capital is Viedma...
of Argentina. The species was named in honor of Alberto Cabaza, who founded the Museo Municipal de Lamarque where the specimen was partially studied.
Anatomy
Considered large for a dromaeosaur, Austroraptor cabazai measured around 5 metres (16.4 ft) in length from head to tail. It is the largest dromaeosaur to be discovered in the Southern HemisphereSouthern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
. Particularly notable about the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
were its relatively short forearms, much shorter in proportion compared to those of other members of its family. The relative length of its arms has caused Austroraptor to be compared to another, more famous short-armed dinosaur, Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
.
The type specimen, labeled MML-195, consisted of a fragmentary skeleton including parts of the dinosaur's skull, a few neck and torso vertebrae, some ribs, a humerus, and assorted bones from both legs. The remains were found among deposits of the Allen Formation
Allen Formation
The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous The Allen Formation is a geological formation in Argentina whose strata date back to the...
of Argentina, dating from the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
to the Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stages of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
period 70 million years ago. However little of the entire skeleton was found, what bones were available for analysis expressed some distinct characteristics that differentiate Austroraptor from other dromaeosaurs. A. cabazais 80 centimeter-long skull was low and elongated, much more so than that of other dromaeosaurs. Several of its skull bones bore some resemblance to that of the smaller troodontid deinonychosaurs
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...
. The front limbs of this taxon were short for a dromaeosaur, with its humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
less than half the length of its femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
. Austroraptor had conical, non-serrated teeth, which Novas et al. compared to those of spinosaurids
Spinosauridae
Spinosauridae is a family of specialised theropod dinosaurs. Members of this family were large, bipedal predators with elongated, crocodile-like skulls, sporting conical teeth with no or only very tiny serrations. The front dentary teeth fanned out, giving the animal a characteristic look...
.
Phylogeny
A cladistic analysis of the specimen's anatomical features by the describers placed Austroraptor within the subfamily UnenlagiinaeUnenlagiinae
Unenlagiinae is a subfamily of Dromaeosauridae. Unenlagiines are one of the most basal lineages of dromaeosaurids. Unenlagiines are known from South America and Madagascar....
of the Dromaeosauridae
Dromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
. Some of these characteristics include the geometry and formation of the specimen's vertebral elements. It was determined that Austroraptor was a close relative of the unenlagiine dromaeosaur Buitreraptor
Buitreraptor
Buitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Buitreraptor was described in 2005. The type species is Buitreraptor gonzalezorum...
.
