Phorusrhacidae

Phorusrhacids ("Rag-Thieves"), colloquially known as "terror birds" as the larger species were apex predators during the Miocene, were a clade of large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2 million years (Ma) ago. They were roughly 1–3 meters (3–10 feet) tall. Their closest modern-day relatives are believed to be the 80 cm-tall seriemas. Titanis walleri, one of the larger species, is known from Texas and Florida in North America. This makes the phorusrhacids the only known example of large South American predators migrating north during the Great American Interchange (which occurred after the volcanic Isthmus of Panama land bridge rose ca. 3 Ma ago). It was once believed that T. walleri only became extinct around the time of the arrival of humans in North America, but subsequent datings of Titanis fossils have failed to provide evidence for their survival more recently than 1.8 Ma ago.

Possible phorusrhacid remains have recently been recovered from the Eocene of Algeria.

A recently discovered species, Kelenken guillermoi from Middle Miocene some 15 million years ago, discovered in Patagonia in 2006, represents the largest bird skull yet found. The fossil has been described as being a 71 cm, nearly intact skull. The beak is roughly 46 cm long and curves in a hook shape that resembles an eagle's beak. Most species described as phorusrhacid birds were smaller, 60 - 90 cm tall, but the new fossil belongs to a bird that probably stood about 3 m tall. Although scientists cannot be sure, they theorize that the large terror birds were extremely nimble and quick runners able to reach speeds of 48 km/h.

Systematics and taxonomy
Following the revision by Alvarenga and Höfling (2003), there are now 5 subfamilies, containing 14 genera and 18 species:
 * Subfamily Brontornithinae — gigantic species, standing over 2.3 m high. Placement in Phorusrhacidae and/or monophyly disputed.
 * Genus Brontornis (Early - Middle Miocene)
 * Genus Paraphysornis (Late Oligocene/Early Miocene of São Paulo State, Brazil)
 * Genus Physornis (Middle - Late Oligocene of Santa Cruz Province, Argentina)
 * Subfamily Phorusrhacinae — giant species 3.2 m high, but somewhat slender and decidedly more nimble than the Brontornithinae
 * Genus Devincenzia (Late Miocene - Early Pliocene of NE Argentina and Arroyo Roman, Uruguay)
 * Genus Kelenken (Middle Miocene of Río Negro province, Argentina (largest known phorusrhacid))
 * Genus Phorusrhacos (Early - Middle Miocene)
 * Genus Titanis (Early Pliocene - Early Pleistocene)
 * Subfamily Patagornithinae — intermediate sized and very nimble species, standing around 1.7 m high
 * Genus Patagornis (Santa Cruz Early - Middle Miocene of Santa Cruz Province, Argentina) - includes Morenomerceraria, Palaeociconia, Tolmodus
 * Genus Andrewsornis (Middle - Late Oligocene of S Argentina)
 * Genus Andalgalornis (Late Miocene - Early Pliocene)
 * Subfamily Psilopterinae — small species, standing 70 - 100 cm high
 * Genus Psilopterus (Deseado Middle Oligocene - Arroyo Chasicó Late Miocene of S and E Argentina)
 * Genus Procariama (Late Miocene - Early Pliocene of Catamarca Province, Argentina)
 * Genus Paleopsilopterus (Middle Paleocene of Itaboraí, Brazil)
 * Subfamily Mesembriornithinae — medium-sized species, standing between 1.2 - 1.5 m high
 * Genus Mesembriornis (Late Miocene - Late Pliocene)

Alvarenga and Höfling did not include the Ameghinornithidae from Europe in the phorusrhacoids; these have meanwhile turned out to be more basal members of Cariamae. Though traditionally considered as members of the Gruiformes, based on both morphological and genetic studies (the latter being based on the seriema ) that they may belong to a separate group of birds (the Cariamae) and their closest living relatives are the Falconidae, Psittaciformes and the Passeriformes

Synonyms
The family Phorusrhacidae have been described under a number of synonyms:


 * Phororhacosidae Ameghino, 1889
 * Pelecyornidae Ameghino, 1891
 * Brontornithidae Moreno & Mercerat, 1891
 * Darwinornithidae Moreno & Mercerat, 1891
 * Stereornithidae Moreno & Mercerat, 1891
 * Phororhacidae Lydekker, 1893 (unjustified emendation)
 * Patagornithidae Mercerat, 1897


 * Hermosiornidae Rovereto, 1914
 * Psilopteridae Dolgopol de Saez, 1927
 * Devincenziidae Kraglievich, 1932
 * Hermosiorniidae Kraglievich, 1932 (unjustified emendation)
 * Mesembriorniidae Kraglievich, 1932
 * Hermosiornithidae Wetmore, 1934 (unjustified emendation)