Austroraptor cabazai was one of the largest known paravians, living in Patagonia near the end of the Cretaceous. Two partial skeletons from the Allen Formation reveal an animal around 5–6 metres long with an approximately 80-centimetre narrow skull, many small conical teeth and arms much shorter than expected for its relatives.
Quick facts
| Scientific name | Austroraptor cabazai Novas et al., 2008 |
|---|---|
| Group | Paraves, Unenlagiidae; traditionally Unenlagiinae within Dromaeosauridae |
| Age | Late Cretaceous, late Campanian–early Maastrichtian |
| Range | Allen Formation, Río Negro, Argentina |
| Length | Approximately 5–6 m |
| Mass | Roughly 300–500 kg |
| Diet | Carnivorous; fish and small prey are plausible |
| Species | A. cabazai |
| Fossil record | Two partial skeletons with skull, vertebral and limb elements |
An unusual giant paravian
Cranial bones support a narrow skull near 80 centimetres with numerous small conical teeth.
The humerus is short relative to the femur; the second specimen confirms a small but functional forearm and hand.
Jaw and tooth shape fit slippery small prey, but no gut contents show a narrow specialisation.
Unenlagiids may be southern dromaeosaurids or early avialans in different analyses.
Discovery and fossils
The holotype MML-195 was found in 2002 at Bajo de Santa Rosa. Fernando Novas and colleagues named it in 2008, honouring museum founder Héctor Cabaza. It preserves much of the skull and lower jaw, vertebrae, ribs, a humerus, pelvis and major hind-limb bones. MML-220, found in the same region, adds forearm, hand, foot and tail elements.
Body plan
The skull was long, low and narrow. Small rounded teeth lacked the large serrations typical of many meat-slicing theropods. The arms were proportionally short, while the hind limbs were large and relatively elongated. This combination makes Austroraptor unlike an enlarged Velociraptor.
Length estimates of 5–6 metres are better expressed as a range; mass estimates of 300–500 kilograms depend on incomplete-body models. Long legs suggest active bipedal movement, not a measured maximum speed. A specialised second toe is expected, but the claw is not complete enough to fix its form.
Diet and habitat
Conical teeth and the long snout could grip fish and other small, slippery animals. Fish-eating is a useful hypothesis, not a recovered meal. Small terrestrial vertebrates and carrion remain possible. Allen Formation environments included rivers, lakes, floodplains and coastal influence, with fish, turtles, crocodile relatives and dinosaurs.
Classification and feathers
Traditional analyses place Austroraptor in Unenlagiinae within Dromaeosauridae. Other work places Unenlagiidae nearer early birds. This disagreement changes the label, not the reality of the two diagnostic skeletons. The broader issue belongs in dinosaur classification.
No feather impressions are preserved. Its position within Paraves makes plumage likely, while density and colour are unknown. Short arms could still carry feathers without being flight-capable.
Evidence, inference and reconstruction
| Direct | Long skull, conical teeth, short arms and large hind limbs |
|---|---|
| Strong inference | Large terrestrial carnivore and feather covering |
| Unresolved | Fish specialisation and dromaeosaurid versus avialan placement |
| Unknown | Colour, speed, social life and usual prey |
Frequently asked questions
When and where did Austroraptor live?
It lived in Patagonia during the late Campanian to early Maastrichtian, around 70 million years ago, and comes from Argentina’s Allen Formation.
How large was Austroraptor?
Its incomplete skeletons support a length of roughly 5–6 metres and a mass of several hundred kilograms, commonly estimated around 300–500 kilograms.
Why were Austroraptor’s arms short?
The evolutionary cause is unknown. Its proportions show real forelimb reduction, possibly associated with increased body size in unenlagiids.
Did Austroraptor eat fish?
Its long jaws and small conical teeth are compatible with catching fish and other small prey, but no stomach contents prove specialised fish-eating.