Austroraptor (AW-stroh-RAP-tor; “Southern thief”) is a genus of dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period, approximately 70 million years ago, in what is now Argentina, South America. The name comes from the Latin word ‘australis’ meaning “southern” and ‘raptor’ meaning “thief” or “plunderer.” Austroraptor was first scientifically described in 2008 by paleontologist Fernando Novas and his colleagues based on fossils found in the Allen Formation. It is one of the largest dromaeosaurs discovered, particularly from the Southern Hemisphere.

Description and Classification

Austroraptor was a large dromaeosaur, a type of meat-eating dinosaur often called “raptors.” Scientists estimate it grew to be about 5 to 6 meters (16 to 20 feet) long, making it significantly larger than more commonly known dromaeosaurs like Velociraptor. Despite its size, Austroraptor had a relatively slender and graceful build compared to some other large dromaeosaurs, such as the powerfully built Utahraptor from North America.

One of its most unusual features was its skull, which was very long and low, measuring about 80 centimeters (31 inches) in length. This is quite different from the shorter, deeper skulls seen in many other dromaeosaurs. Its teeth were small, conical, and lacked serrations, suggesting it might have hunted or eaten differently than its relatives which often had larger, blade-like teeth for tearing flesh. Another surprising feature was its forelimbs (arms), which were quite short for a dromaeosaur of its size, especially when compared to dinosaurs like Deinonychus. Like other members of its family, Austroraptor would have had a sickle-shaped claw on the second toe of each foot, although this claw was proportionally smaller than in many of its relatives from the Northern Hemisphere.

Austroraptor belongs to the family Dromaeosauridae, a group of theropod dinosaurs known for their bird-like features, including feathers (though no direct evidence of feathers has been found for Austroraptor, it is inferred based on its close relatives). Within this family, Austroraptor is often classified as part of the Unenlagiinae, a subfamily of dromaeosaurs primarily found in the Southern Hemisphere (Gondwana). Other unenlagiines include dinosaurs like Unenlagia and Buitreraptor, which also show some unique adaptations compared to dromaeosaurs from Laurasia (the northern continents).

Distinguishing Features

• An unusually long and low skull, distinct from the shorter, boxier skulls of many other dromaeosaurs.
• Relatively small, conical teeth that were not serrated, suggesting a specialized diet.
• Proportionally short forelimbs compared to its hindlimbs and overall body size, which is uncommon for dromaeosaurs.
• Large body size, ranking it among the largest known dromaeosaurids.
• A more slender build compared to some robust dromaeosaurs found in North America.

Paleoenvironment and Diet

Austroraptor lived in what is now the Río Negro Province of Argentina during the Late Cretaceous period. The fossils were discovered in the Allen Formation, which represents an ancient coastal plain environment. This area likely featured rivers, floodplains, swamps, and estuaries, with a humid climate. Austroraptor shared this habitat with a variety of other dinosaurs, including large sauropods like titanosaurs (such as Aeolosaurus), hadrosaurs (duck-billed dinosaurs), and other predatory theropods like abelisaurids.

As a dromaeosaur, Austroraptor was a carnivore. However, its unique features, particularly its long snout and small, conical teeth, have led paleontologists to suggest it may have specialized in catching different types of prey than other dromaeosaurs. Some scientists propose that Austroraptor might have hunted smaller, quicker animals, or perhaps even included fish in its diet (piscivory), similar to the way some modern crocodiles or even spinosaurid dinosaurs are thought to have hunted. Its large size would have still made it a dangerous predator, capable of taking down medium-sized prey.

Significance and Ongoing Research

The discovery of Austroraptor has been very important for understanding the diversity and evolution of dromaeosaurid dinosaurs, especially in the Southern Hemisphere. It showed that these “raptor” dinosaurs in Gondwana evolved unique body plans and likely filled different ecological roles compared to their relatives in North America and Asia. Its unusual combination of features, like the long skull and short arms, challenges previous assumptions about dromaeosaur anatomy and behavior.

Ongoing research on Austroraptor focuses on several areas. Scientists are keen to find more complete fossil material to better understand its full anatomy and how it moved. Further studies on its skull and teeth aim to clarify its diet and hunting strategies. Comparing Austroraptor with other dromaeosaurs, particularly other Gondwanan forms like Unenlagia and those from Laurasia like Achillobator, helps to piece together the evolutionary history of this fascinating group of dinosaurs and how they adapted to different environments across the globe.