Phorusrhacos (pronounced "FOR-rus-RAH-kos") ("Rag-Bearer") was a genus of giant flightless predatory birds that lived in Patagonia, containing the single species Phorusrhacos longissimus. Their closest living relatives are Seriema birds. It was much larger than the seriemas, however, and looked more like an ostrich in appearance. These birds lived in woodlands and grasslands.
Among the bones found in the stratum of the Santa Cruz Formation (now considered as mainly of mid-Miocene date) was the piece of a mandible which Florentino Ameghino (1887) at first described as that of an edentate mammal. In 1891, it was recognized to be a bird. Remains are known from several localities in the Santa Cruz Province, of Argentina.
Phorusrhacos stood around 2.5 meters (8 ft) tall and weighed approximately 130 kilograms (280 lbs) (Alvarenga & Höfling, 2003). It was nicknamed the "Terror Bird" for obvious reasons: it was one of the largest carnivorous birds to have ever existed, along with Titanis, and its rudimentary wings formed arm-like structures with claws shaped like a meat hook for tackling prey, which was then killed with the massive beak. It ate small mammals and carrion. It is thought that the bird grasped its prey with its beak and smashed it to the ground repeatedly like its modern relatives, the Seriemas. It had an enormous skull up to sixty centimeters long, armed with a powerful, hook-tipped beak. The structure of the beak and the large claws on the toes show that this was a bird of prey. It raced over the grassy plateaus and hills of Patagonia, catching small reptiles and mammals.