Phorusrhacidae

Phorusrhacidae, colloquially known as terror birds, is a family of large carnivorous, mostly flightless birds that includes possibly several subfamilies containing many genera, including the eponymous Phorusrhacos. The exact number of genera is uncertain, as some taxa such as Brontornis may be different forms of bird instead. All phorusrhacids lived during the Cenozoic era in the Americas. However, fossils have been recorded from Africa and Europe that may belong to phorusrhacids. Possible specimens have also been discovered from the La Meseta Formation of Seymour Island, Antarctica, suggesting that this group had a wider geographical range in the Paleogene. While a majority of phorusrhacids are known from South America, Titanis is known from the southern United States. Their definitive fossil records range from the Middle Eocene to the Late Pleistocene around 43 to 0.025 million years ago, though some specimens suggest that they were present since the Early Eocene. Phorusrhacids ranged widely in size, with the smallest members like Psilopterus measuring 1 meter (3.3 ft) tall whereas giants like Devincenzia possibly reached 3 meters (9.8 ft) tall. Their closest modern-day relatives are believed to be the 80-centimetre-tall (31 in) seriemas. Phorusrhacids were bipedal carnivores with large skulls that terminated in elongated, sharp beaks. Although it varies between genera, most phorusrhacids had elongated, lithe hindlimbs with a sickle claw on their innermost toe. In contrast, their arms were relatively small and bore no functional digits. Phorusrhacidae was coined by Argentine paleontologist Florentino Ameghino in 1889 and it initially included just two genera: Phorusrhacos and Tolmodus (a synonym of Patagornis). At the time, Ameghino believed it was a family of giant, edentulous xenarthran mammals possibly related to anteaters. In 1891, Argentine paleontologist Francisco Moreno pointed out that phorusrhacids were giant birds instead. The two scientists engaged in a heated scientific rivalry for decades,...