Belongs within: Cariamiformes.
The Phorusrhacidae include the ‘terror birds’ of South America, flightless carnivorous birds that lived from the mid-Palaeocene to the Upper Pliocene/Lower Pleistocene. The latest surviving species, Titanis walleri, is also notable for being found in southern North America. Some phorusrhacids reached significant sizes, with heights comparable to a human; other species were smaller, possibly a little over two feet in height (Alvarenga & Höfling 2003).
Alvarenga & Höfling (2003) recognised five subfamilies within the Phorusrhacidae. The smallest phorusrhacids belonged to the Psilopterinae, and the largest to the Phorusrhacinae and Brontornithinae. The Phorusrhacinae were of a more slender and cursorial build than the heavy, robust Brontornithinae. The Patagornithinae are medium-sized phorusrhacids with a more slender build than Phorusrhacinae.
Characters (Alvarenga & Höfling 2003): Large or even gigantic build; body slim in frontal view, especially the premaxila, pelvis and thorax being laterally flattened; premaxilla bulky, especially high, with a pointed strong apex in the form of a hook; jaw with very solid symphysis; ample and pervious nostrils (septum absent); palate desmognate; basipterigoid processes well-developed; pterigoids with evident articulation for basipterigoid process in mid-portion; ribs lacking uncinate processes; pubis atrophied in cranial half; wings reduced; coracoid with extreme reduction of procoracoidal and acrocoracoidal processes, possessing an ample scapular facet, in the form of a groove in the apex; humerus with internal tuberosity bulging proximally, proximal half of diaphysis being strongly bent and processus flexorius distally prominent; tarsometatarsus with triangular-shaped hypotarsus when viewed from below and without tendon grooves; strongly curved ungual phalanx.
<==Phorusrhacidae (see below for synonymy)
| i. s.: Kelenken Bertelli, Chiappe & Tambussi 2007BCT07
| `--*K. guillermoi Bertelli, Chiappe & Tambussi 2007BCT07
|--Patagornithinae [Tolmodinae]BCT07
| |--Patagornis Moreno & Mercerat 1891 [incl. Morenomerceraria Lambrecht 1933, Tolmodus Ameghino 1891]AH03
| | `--*P. marshi Moreno & Mercerat 1891AH03 (see below for synonymy)
| |--Andalgalornis Patterson & Kraglievich 1960AH03
| | `--A. steulletti (Kraglievich 1931) (see below for synonymy)AH03
| `--Andrewsornis Patterson 1941AH03
| |--*A. abbotti Patterson 1941AH03
| `--‘Aucornis’ solidus Ameghino 1899 (n. d.)AH03, A06
|--Phorusrhacinae [Phororhacinae]FP64
| |--Phorusrhacos Ameghino 1887AH03 (see below for synonymy)
| | `--*P. longissimus Ameghino 1887AH03 (see below for synonymy)
| |--Titanis Brodkorb 1963AH03
| | `--*T. walleri Brodkorb 1963AH03
| `--Devincenzia Kraglievich 1931A06 [incl. Onactornis Cabrera 1939AH03]
| `--D. pozzii (Kraglievich 1931)A06 (see below for synonymy)
|--Brontornithinae [Brontorniinae]FP64
| |--Brontornis Moreno & Mercerat 1891 [incl. Rostrornis Moreno & Mercerat 1891]AH03
| | `--*B. burmeisteri Moreno & Mercerat 1891 (see below for synonymy)AH03
| |--Physornis Ameghino 1895 [incl. Aucornis Ameghino 1898]AH03
| | `--*P. fortis Ameghino 1895 [incl. Aucornis euryrhynchus Ameghino 1899]AH03
| `--Paraphysornis Alvarenga 1993AH03
| `--*P. brasiliensis (Alvarenga 1982) [=Physornis brasiliensis]AH03
|--Mesembriornis Moreno 1889AH03 (see below for synonymy)
| |--*M. milneedwardsi Moreno 1889 (see below for synonymy)AH03
| `--M. incertus (Rovereto 1914) [=Prophororhacos incertus]AH03
`--PsilopterinaeBCT07
|--Ciconiopsis antarctica Ameghino 1899M09
|--Smiliornis Ameghino 1891AH03
| `--S. penetrans Ameghino 1899AH03
|--Procariama Rovereto 1914AH03
| `--*P. simplex Rovereto 1914AH03
|--Riacama Ameghino 1899AH03
| `--R. caliginea Ameghino 1899AH03
|--Lophiornis Ameghino 1891AH03
| `--L. obliquus Ameghino 1891AH03
|--Paleopsilopterus Alvarenga 1985AH03
| `--*P. itaboraiensis Alvarenga 1985AH03
`--Psilopterus Moreno & Mercerat 1891 (see below for synonymy)AH03
|--P. bachmanni (Moreno & Mercerat 1891)AH03 (see below for synonymy)
|--P. affinis (Ameghino 1899) [=Phororhacos affinis]AH03
|--P. colzecus Tonni & Tambussi 1988AH03
|--P. guaraniticus (Ameghino 1899) [=Pseudolarus guaraniticus]M09
`--P. lemoinei (Moreno & Mercerat 1891)AH03 (see below for synonymy)
Andalgalornis steulletti (Kraglievich 1931) [=Phororhacos steulletti; incl. P. deautieri Kraglievich 1931, *Andalgalornis ferox Patterson & Kraglievich 1960]AH03
*Brontornis burmeisteri Moreno & Mercerat 1891 [incl. Rostrornis floweri Moreno & Mercerat 1891, B. platyonyx Ameghino 1895]AH03
Devincenzia pozzii (Kraglievich 1931)A06 [=Phororhacos pozziiA06, Onactornis pozziiA06; incl. O. depressus Cabrera 1939AH03, *Devincenzia gallinali Kraglievich 1932AH03, Phororhacos longissimus mendocinus Kraglievich 1931AH03, Onactornis mendocinusA06]
Mesembriornis Moreno 1889AH03 [incl. Hermosiornis Moreno 1889AH03, Paleociconia Moreno 1889AH03, Prophororhacos Rovereto 1914AH03; Hermosiornithinae, MesembriornithinaeBCT07, Prophororhacinae]
*Mesembriornis milneedwardsi Moreno 1889 [incl. *Paleociconia australis Moreno 1889, Prophororhacos australis, Hermosiornis milneedwardsi Rovereto 1914, Driornis pampeanus Moreno & Mercerat 1891, Hermosiornis rapax Kraglievich 1946]AH03
*Patagornis marshi Moreno & Mercerat 1891AH03 [incl. Paleociconia cristata Moreno & Mercerat 1891BCT07, AH03, Tolmodus inflatus Ameghino 1891AH03, Phororhacos inflatusAH03, Phorusrhacos inflatusM09]
Phorusrhacidae [Brontornithes, Brontornithidae, Darwinornithidae, Devincenziidae, Hermosiornidae, Hermosiorniidae, Hermosiornithidae, Mesembriornidae, Mesembriornithidae, Mesembriornithinae, Paleociconiinae, Patagornithidae, Pelecyornidae, Pelecyornithidae, Phororhaci, Phororhacidae, Phororhacoidea, Phororhacosidae, Phorusrhacoidae, Phorusrhacoidea, Phorusrhacosidae, Psilopteridae, Psilopteriidae, Stereornithidae]
Phorusrhacos Ameghino 1887AH03 [=Phororhacos Ameghino 1889AH03; incl. Callornis Ameghino 1895AH03, Darwinornis Moreno & Mercerat 1891AH03, Dryornis Moreno & Mercerat 1891A94, Eucallornis Ameghino 1901AH03, Liornis Ameghino 1895AH03, Owenornis Moreno & Mercerat 1891AH03, Stephanornis Mercerat 1893A94, Stereornis Moreno & Mercerat 1891AH03, Titanornis Mercerat 1893AH03; Liorninae, Liornithidae]
Phorusrhacos longissimus Ameghino 1887AH03 [=Phororhacos longissimusAH03; incl. Owenornis affinis Moreno & Mercerat 1891AH03, Darwinornis copei Moreno & Mercerat 1891AH03, *Liornis floweri Ameghino 1895A94, AH03, Stereornis gaundryi Moreno & Mercerat 1891AH03, *Callornis giganteus Ameghino 1895A94, AH03, Eucallornis giganteusAH03, Owenornis lydekkeri Moreno & Mercerat 1891AH03, Liornis minor Dolgopol de Saez 1927AH03, Titanornis mirabilis Mercerat 1893AH03, Phororhacos platygnathus Ameghino 1891 AH03, Mesembriornis quatrefragesi Moreno & Mercerat 1891AH03, Stereornis rollieri Moreno & Mercerat 1891AH03, Phororhacos sehuensis Ameghino 1891AH03, Darwinornis socialis Moreno & Mercerat 1891AH03, Mesembriornis studeri Moreno & Mercerat 1891AH03, D. zitteli Moreno & Mercerat 1891AH03]
Psilopterus Moreno & Mercerat 1891 [incl. Pelecyornis Ameghino 1891, Pseudolarus Ameghino 1891, Staphylornis Mercerat 1897]AH03
Psilopterus australis Moreno & Mercerat 1891A06, AH03 [=Pelecyornis australisA94; incl. *Pseudolarus eocaenus Ameghino 1891A06, A94]
Psilopterus bachmanni (Moreno & Mercerat 1891)AH03 [=Patagornis bachmanniAH03; incl. *Ps. communis Moreno & Mercerat 1891AH03, BCT07, A06, Pelecyornis communisA94, Phororhacos delicatus Ameghino 1891AH03, Psilopterus intermedius Moreno & Mercerat 1891AH03, Ps. minutus Ameghino 1891AH03, Pelecyornis minutusA94, Pe. pueyrredonensis Sinclair & Farr 1932AH03]
Psilopterus lemoinei (Moreno & Mercerat 1891)AH03 [=Patagornis lemoineiAH03; incl. Psi. australis Moreno & Mercerat 1891BCT07, AH03, Pelecyornis australisA94, *Pseudolarus eocaenus Ameghino 1891A06, A94, Staphylornis erythacus Mercerat 1897AH03, S. gallardoi Mercerat 1897AH03, Phororhacos modicus Ameghino 1895AH03, Pelecyornis tenuirostris Sinclair & Farr 1932AH03, Pe. tubulatus Ameghino 1895AH03]
*Type species of generic name indicated
References
[A06] Agnolin, F. 2006. Posición sistemática de algunas aves fororracoideas (Ralliformes; Cariamae) Argentinas. Revista del Museo Argentino de Ciencias Naturales, n. s. 8 (1): 27–33.
[AH03] Alvarenga, H. M. F., & E. Höfling. 2003. Systematic revision of the Phorusrhacidae (Aves: Ralliformes). Papéis Avulsos de Zoologia 43 (4): 55–91.
[A94] Ameghino, F. 1894. Sur les oiseaux fossiles de Patagonie et la aune mammalogique des couches a Pyrotherium. Boletín del Instituto Geográfico Argentino 15 (11–12): 501–602.
[BCT07] Bertelli, S., L. M. Chiappe & C. Tambussi. 2007. A new phorusrhacid (Aves: Cariamae) from the Middle Miocene of Patagonia, Argentina. Journal of Vertebrate Paleontology 27 (2): 409–419.
[FP64] Fisher, J., & R. T. Peterson. 1964. The World of Birds: A comprehensive guide to general ornithology. Macdonald: London.
[M09] Mayr, G. 2009. Paleogene Fossil Birds. Springer.