Temporal range: 62–2Ma Middle Paleocene - Early Pleistocene
|Reconstructed skeleton of Titanis, Florida Museum of Natural History|
Phorusrhacids, colloquially known as terror birds, were a clade of large carnivorous flightless birds that were the largest species of apex predators in South America during the Cenozoic, 62–2 million years (Ma) ago.
They were roughly 1–3 metres (3.3–9.8 ft) 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.
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 (28 in), nearly intact skull. The beak is roughly 46 cm (18 in) long and curves in a hook shape that resembles an eagle's beak. Most species described as phorusrhacid birds were smaller, 60–90 cm (2.0–3.0 ft) tall, but the new fossil belongs to a bird that probably stood about 3 m (9.8 ft) tall. Scientists theorize that the large terror birds were extremely nimble and quick runners able to reach speeds of 48 km/h (30 mph).
The etymology of the name Phorusrhacidae is based on the type genus Phorusrhacos. When first described by Florentino Ameghino in 1887, the etymology of Phorusrhacos was not given. Current thinking is that the name is derived from a combination of the Greek words "phoros", which means bearer or bearing, and "rhacos", which translates to wrinkles, scars or rents.
Systematics and taxonomy 
- Subfamily Brontornithinae — gigantic species, standing over 2.3 metres (7.5 ft) high. Placement in Phorusrhacidae and/or monophyly disputed.
- Subfamily Phorusrhacinae — giant species 3.2 metres (10 ft) high, but somewhat slender and decidedly more nimble than the Brontornithinae
- Subfamily Patagornithinae — intermediate sized and very nimble species, standing around 1.7 metres (5.6 ft) high
- Subfamily Psilopterinae — small species, standing 70–100 centimetres (2.3–3.3 ft) high
- Subfamily Mesembriornithinae — medium-sized species, standing between 1.2–1.5 metres (3.9–4.9 ft) 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, according to the last nuclear studies, are a clade conformed by Falconidae, Psittaciformes and Passeriformes
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)
- GeoWhen Database - Gelasian December 2007, from Internet archive
- Ameghino, F (1889). "Contribuición al conocimiento de los mamíferos fósiles de la República Argentina". Actas Academia Nacional Ciencias de Córdoba (in Spanish) 6: 1–1028.
- Blanco, R. E.; Jones, W. W. (2005). "Terror birds on the run: a mechanical model to estimate its maximum running speed". Proceedings of the Royal Society B 272 (1574): 1769–1773. doi:10.1098/rspb.2005.3133.
- Baskin, J. A. (1995). "The giant flightless bird Titanis walleri (Aves: Phorusrhacidae) from the Pleistocene coastal plain of South Texas". Journal of Vertebrate Paleontology 15 (4): 842–844. doi:10.1080/02724634.1995.10011266.
- MacFadden, Bruce J.; Labs-Hochstein, Joann; Hulbert, Richard C.; Baskin, Jon A. (2007). "Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange" (PDF). Geology 35 (2): 123–126. doi:10.1130/G23186A.1.
- Mourer-Chauviré, C. et al. (2011) A Phororhacoid bird from the Eocene of Africa. Naturwissenschaften doi:10.1007/s00114-011-0829-5
- Bertelli, Sara; Chiappe, Luis M; Tambussi, Claudia (2007). "A New Phorusrhacid (Aves: Cariamae) from the Middle Miocene of Patagonia, Argentina". Journal of Vertebrate Paleontology 27 (2): 409–419. doi:10.1671/0272-4634(2007)27[409:ANPACF]2.0.CO;2.
- Ben Creisler, "Phorusrhacos “wrinkle bearer (jaw)”: Etymology and Meaning", Dinosaur Mailing List, 26 June 2012 http://dml.cmnh.org/2012Jun/msg00306.html
- Alvarenga, Herculano M.F.; Höfling, Elizabeth (2003). "Systematic revision of the Phorusrhacidae (Aves: Ralliformes)". Papéis Avulsos de Zoologia 43 (4): 55–91. doi:10.1590/S0031-10492003000400001.
- Mayr, Gerald (2005-04-15). "Old World phorusrhacids (Aves, Phorusrhacidae): a new look at Strigogyps ("Aenigmavis") sapea (Peters 1987)" (abstract). PaleoBios 25 (1): 11–16. Retrieved 2008-07-04.
- Hackett, Shannon J.; et al. (2008-06-27). "A Phylogenomic Study of Birds Reveals Their Evolutionary History". Science 320 (5884): 1763–1768. doi:10.1126/science.1157704. PMID 18583609. Retrieved 2008-10-18.
- Alexander Suh et al. (2011-08-23). "Mesozoic retroposons reveal parrots as the closest living relatives of passerine birds". Nature Communications 2 (8). doi:10.1038/ncomms1448. PMC 3265382. PMID 21863010.
|Wikimedia Commons has media related to: Phorusrhacidae|
- Hooper Museum
- Terror Birds: Bigger and Faster (Science)
- Darren Naish: Tetrapod Zoology: "terror birds"
- Darren Naish: Tetrapod Zoology: "Raven, the claw-handed bird, last of the phorusrhacids" includes links to other articles on phorusrhacids