Phorusrhacoids, or Terror Birds

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Phorusrhacoids, or Terror Birds

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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 into meathook-like structures that likely could be outstretched like arms to perform a hacking motion which theoretically was helpful in bringing down prey. Most of the smaller and some of the larger species are believed to have been fast runners.

Their closest modern-day relatives are the seriemas.

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.

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.
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