A different kind of raptor
In December 2002, paleontologists discovered the partial skeleton of a large, unusual predator in the Bajo de Santa Rosa locality of Río Negro Province, Argentina. Unearthed from the Allen Formation, a geological layer dating to the late Campanian-Maastrichtian ages about 70 million years ago, the fossil was formally named Austroraptor cabazai in 2008. The name translates to "southern thief," honoring its discovery in the Southern Hemisphere.
Austroraptor was a large dromaeosaurid, a family of feathered theropods popularly known as "raptors." It measured an estimated 5 to 6 meters (16 to 20 feet) in length and may have weighed between 300 and 520 kilograms (660 to 1,150 pounds). This makes it one of the largest dromaeosaurids known from anywhere in the world. Its most distinctive feature is its skull, which is disproportionately long and low. At an estimated 80 centimeters (31 inches), the skull is more elongated than that of any other dromaeosaurid. This elongated snout, combined with numerous small, conical teeth, shows a strong similarity to the skulls of spinosaurids—dinosaurs known to have been at least partially fish-eaters. This suggests Austroraptor was a specialized predator, likely hunting fish and other small prey in the coastal environments of Late Cretaceous Argentina.
An unconventional hunter
Another of Austroraptor's strange characteristics is its unusually short forelimbs. Its humerus (upper arm bone) was less than half the length of its femur (thigh bone), giving it proportionally shorter arms than even Tyrannosaurus rex. This is a departure from the long, grasping arms seen in many of its Northern Hemisphere relatives like Deinonychus and Velociraptor, which are thought to have used their arms to restrain prey. Austroraptor likely relied more on its specialized jaws for hunting.
The fossil remains of Austroraptor were found in the Allen Formation, which preserves a record of a complex coastal environment. Sedimentary evidence points to a mix of estuaries, tidal flats, and river systems under a semi-arid climate. This environment supported a diverse fauna. Alongside Austroraptor, paleontologists have found fossils of titanosaur sauropods, hadrosaurs, ankylosaurs, turtles, crocodiles, and various fish. The presence of both freshwater and marine life, including plesiosaurs, in the same formation indicates Austroraptor lived at the boundary between land and sea, a perfect setting for a large, wading, fish-eating predator.