Birds Guide

Phorusrhacoids Conservation status: Fossil  Fossil range: Paleogene-Mid Neogene
Drawing of Phorusrhacos longissimus, a phorusrhacoid, by Charles R. Knight
Scientific classification
Kingdom: Animalia   Phylum: Chordata   Class: Aves   Order: Gruiformes   Family: Phorusrhacidae Ameghino, 1889
Synonyms
Phororhacosidae Ameghino, 1889 Phororhacidae Lydekker, 1893 Brontornithidae Moreno & Mercerat, 1891 Darwinornithidae Moreno & Mercerat, 1891 Stereornithidae Moreno & Mercerat, 1891 Patagornithidae Mercerat, 1897 Devincenziidae Kraglievich, 1932 Mesembriorniidae Kraglievich, 1932 Phorusrhacidae Brodkorb, 1963

Phorusrhacoids, or Terror Birds, were large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2.5 million years ago. They were roughly 1–3 meters (3–10 feet) tall. Titanis walleri, one of the largest species, is known from North America, marking one of the comparatively rare examples where animals that evolved in South America managed to spread north after the Isthmus of Panama landbridge formed. The ancestors of T. walleri have not been found; however, it is possible that more North American species await discovery. Only a few bones of T. walleri have been discovered at scattered locations in Florida and at a site along the Texas coast. No complete skeleton exists of North America's only known phorusrhacoid.

Phorusrhacoids are colloquially known as "terror birds", because their larger species were top-level predators and among the most fearsome carnivores of their habitat. Their wings had evolved to meathook-like structures that could be outstretched like arms and were able to perform a hacking motion which apparently was helpful in bringing down prey. Most of the smaller and some of the larger species were fast runners.

Their closest modern-day relatives are the seriemas, which do not, however, belong to the same lineage.

A new (2006) specimen from Patagonia represents the largest bird skull found yet; it has not been formally described yet but might belong to a new taxon. [1]

Taxonomy

Following the revision by Alvarenga and Höfling (2003), there are now 5 subfamilies, containing 13 genera and 17 species:

• Subfamily Brontornithinae - gigantic species, standing over 2 meters high
  • Genus Brontornis
    • Brontornis burmeisteri
  • Genus Physornis
    • Physornis fortis
  • Genus Paraphysornis
    • Paraphysornis brasiliensis
• Subfamily Phorusrhacinae - gigantic species, but somewhat smaller and decidedly more nimble than the Brontornithinae
  • Genus Phorusrhacos
    • Phorusrhacos longissimus
  • Genus Devincenzia
    • Devincenzia pozzi
  • Genus Titanis
    • Titanis walleri
• Subfamily Patagornithinae - medium-sized and very nimble species, standing around 1.5 meters high
  • Genus Patagornis
    • Patagornis marshi
  • Genus Andrewsornis
    • Andrewsornis abbotti
  • Genus Andalgalornis
    • Andalgalornis steulleti
• Subfamily Psilopterinae - small species, standing 70-100 centimeters high
  • Genus Psilopterus
    • Psilopterus bachmanni
      Psilopterus lemoinei
      Psilopterus affinis
      Psilopterus colzecus
  • Genus Procariama
    • Procariama simplex
  • Genus Paleopsilopterus
    • Paleopsilopterus itaboraiensis
• Subfamily Mesembriornithinae - medium-sized species, standing between 1 and 1.5 meters high
  • Genus Mesembriornis
    • Mesembriornis milneedwardsi
      Mesembriornis incertus

Alvarenga and Höfling do not include the Ameghinornithinae and Aenigmavis sapea from Europe in the phorusrhacoids; they conclude that the former are close relatives, and the latter is of uncertain affiliation.

References

• Alvarenga, Herculano M. F. & Höfling, Elizabeth (2003): Systematic revision of the Phorusrhacidae (Aves: Ralliformes). Papéis Avulsos de Zoologia 43(4): 55-91 PDF fulltext
• Ameghino, F. (1889): "Contribuición al conocimiento de los mamíferos fósiles de la República Argentina", Actas Academia Nacional Ciencias de Córdoba 6: 1-1028.

External links

• Hooper Museum
• "Huge 'Terror Bird' Fossil Discovered in Patagonia" by Christopher Joyce of NPR
• Palaeontology: Skull morphology of giant terror birds {Nature)
• Terror Birds: Bigger and Faster (Science)