Austroraptor

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

Name, discovery and later study

Austroraptor combines Latin auster, “south” or “southern wind”, with raptor, “robber” or “grasper”. The usual translation is “southern robber”. The species name cabazai honours Héctor Tito Cabaza, founder of the municipal museum in Lamarque.

Holotype MML-195 was discovered in 2002 near Bajo de Santa Rosa. Fernando Novas and colleagues named the genus in a paper published online late in 2008. It immediately stood out as an enormous unenlagiid with an elongated head, small teeth and a short humerus, unlike smaller relatives such as Buitreraptor.

A second individual, MML-220, was found in the same region in 2008. It was somewhat smaller but preserved forearm, hand, foot and tail parts missing from the holotype. A detailed redescription by Matías Motta and Fernando Novas in 2025 reassessed both skeletons and highlighted the combination of gigantic size and reduced forelimbs.

What the two skeletons preserve

MML-195 includes much of the skull and lower jaw: frontals, postorbital, lacrimals, both maxillae with teeth, dentaries and bones from the rear of the mandible. Cervical and dorsal vertebrae, ribs and gastralia represent the axial skeleton.

Postcranial remains include a humerus, a hand ungual, part of the pubis, femur and tibia, ankle elements, the third metatarsal and several toe phalanges. MML-220 adds the ulna and radius, separate hand elements, caudal vertebrae and further foot bones.

No complete skeleton exists. Large portions of the trunk and tail, along with some limb elements, must be restored comparatively. The two specimens are nevertheless diagnostic and reveal the genus’s unusual proportions.

Size and body proportions

The original description estimated the holotype near five metres long. Later reconstructions often approach six metres, so 5–6 metres is more honest than one exact figure. Mass is still less secure. Values around 300–500 kilograms are plausible model outputs based partly on the femur, not a directly preserved body volume.

Austroraptor was among the largest known paravians. Large, relatively long hind limbs carried a horizontally balanced body, with the tail acting as a counterweight. The proportions permit active bipedal movement but do not provide a maximum speed.

The forelimbs were remarkably short. The humerus is much shorter than the femur, and the second specimen confirms that the forearm and hand retained their normal elements within a proportionally small limb. They were not absent or anatomically useless, but probably played less of a role in prey capture than the long arms of smaller unenlagiids.

The 2025 study explored a possible association between increased body size and relative arm reduction within Unenlagiidae. It documents a pattern, not a known evolutionary cause.

Skull and teeth

The skull was long, low and narrow, with a reconstructed length near 80 centimetres. An especially elongated maxilla formed much of the side of the snout. The jaws carried numerous comparatively small conical teeth without the coarse cutting serrations of many large flesh-slicing theropods.

The crowns were unusually rounded in cross-section even among unenlagiids. A long snout and conical teeth could hold fish or other small slippery prey. This functional match explains the frequent fish-eating reconstruction, but no stomach content or feeding trace demonstrates a specialised diet.

Forelimbs, hind limbs and raised toe

The short hand still carried claws and muscle attachments. It should not be described as wholly non-functional, although it offered less reach than the arms of long-limbed relatives. A feathered forelimb is plausible without implying flight.

The femur and tibia were large and the metatarsus comparatively elongated. As an unenlagiid paravian, Austroraptor probably retained a functionally enlarged second toe. The characteristic claw is not complete enough to fix its size or use for this genus. Long legs indicate mobility, while several hundred kilograms of body mass separate it from tiny fast-running paravians.

Classification and recognised species

Only Austroraptor cabazai is recognised. The two individuals belong to the same diagnostic form rather than separate named species. At its description Austroraptor entered Unenlagiinae within Dromaeosauridae, the traditional arrangement for these southern paravians.

Alternative analyses have long placed unenlagiids closer to birds. A large 2025 phylogenetic study recovered Unenlagiidae as early-diverging Avialae. Other matrices continue to place them within Dromaeosauridae, so this result has not ended the debate. Austroraptor is securely a paravian and an unenlagiid; whether that lineage is a southern dromaeosaur branch or nearer early birds remains unresolved.

Environment and potential food

The Allen Formation records late Campanian to early Maastrichtian landscapes in Patagonia, around 70 million years ago. Its deposits formed in varied continental and coastal settings including rivers, lakes, floodplains and shallow waters influenced by a nearby sea.

Titanosaurs, hadrosauroids, other theropods, crocodylomorphs, turtles and fish occur in the formation. Their presence shows ecological possibilities, not direct feeding links with Austroraptor. The animal was carnivorous and may have caught fish and small terrestrial vertebrates or scavenged when opportunities arose.

Two skeletons do not form a mass assemblage and reveal nothing secure about pack hunting. Daily activity, calls, courtship and parental care are unknown.

Feathers and external appearance

No feather impression is associated with either specimen. Its position within Paraves makes at least some plumage probable, but Austroraptor was much larger than most paravians with direct body coverings. Feather density in a mature individual cannot be specified.

Colour and pattern are entirely unknown. Short arms may still have carried feathers, yet they were not wings capable of powered flight. Head soft tissues and the full tail outline also remain reconstructed.

Common errors and scientific importance

The most persistent mistake is to enlarge the familiar movie Velociraptor. Austroraptor had a much longer, lower skull, conical teeth and far shorter arms. Another overstatement turns plausible fish consumption into an obligatory specialised diet.

Calling it simply a dromaeosaurid hides the live phylogenetic dispute, while calling it definitively an early bird overstates one set of analyses. Exact speed and mass values likewise exceed the incomplete skeletons.

Austroraptor demonstrates that Gondwanan paravians could reach very large body sizes and evolve an unexpected combination of cranial and limb proportions. The 2025 redescription also makes it a key case for studying how forelimbs changed as body size increased and for testing the competing positions of Unenlagiidae.

Evidence, inference and reconstruction