Phorusrhacos

Phorusrhacos (meaning "bearer of scars" or "bearer of wrinkles") is an extinct genus of phorusrhacid, a group of predominantly large, predatory flightless birds commonly known as terror birds. It lived during the Early to Middle Miocene, approximately 18–13 million years ago, in what is now southern Argentina. The first fossil attributed to the genus, an isolated fragment of the mandible (lower jaw), was discovered in 1887 by Argentine paleontologist Carlos Ameghino in sediments of the Santa Cruz Formation in Santa Cruz Province, Argentina. Later that year, his brother, Florentino Ameghino, formally described the specimen as the new genus and species Phorusrhacos longissimus. Florentino initially interpreted the fossil as belonging to a giant, toothless sloth and assigned the genus to its own family, Phorusrhacidae. In 1891, however, Argentine naturalist Francisco Moreno recognized that the specimen was avian rather than mammalian. Since its initial description, Phorusrhacos has become one of the best-known phorusrhacid genera, with fossils documented from numerous localities in southern Argentina. Phorusrhacos is estimated to have stood 1.4–1.9 meters (4.6–6.2 ft) tall and weighed around 93 kilograms (205 lb), placing it among the largest known phorusrhacids. Despite its size, it was more lithe and cursorial (built for running) than the similarly sized Kelenken and Devincenzia. Like other phorusrhacids, it had a tall, elongated skull with a sharply hooked beak. The skull was laterally compressed, particularly when viewed from the front. Its cervical vertebrae were short, thick, and broad, features that may have strengthened the neck for delivering powerful strikes. The hindlimbs were long and slender, with the tarsometatarsus measuring approximately 70% the length of the tibiotarsus and possessing a relative slender shaft. During the Miocene, the region of present-day Santa Cruz Province was characterized by a mosaic of savanna-like grasslands, shrublands, and woodlands. At the time, South America remained geographically...