Huge flightless terror birds were South America's top predators for millions of years and at nearly three metres tall certainly lived up to their name. Their modern relatives, the seriemas, kill their prey by smashing it repeatedly against the ground, which may well have been the terror birds' technique too. The terror birds lived between 27 million and 15,000 years ago and spread into North America when the two continents joined. One of these birds boasts the record for the largest bird skull ever found, measuring 71cm long with a wicked, curved 45cm beak.
Scientific name: Phorusrhacidae
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Additional data source: Animal Diversity Web
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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. However, there exist additional findings that date from 450,000 years ago and 17,000 years ago, that suggest that at least some terror birds survived until the late Pleistocene in Uruguay.
Terror birds may have even made their way into Africa, with the genus Lavocatavis recently discovered in Algeria, although its status as a true phorusrhacid is questionable.
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. Researchers have compared Phorusrhacidae with the living families of Cariamidae and Sagittaridae, but their differences in body mass are too drastic, and thus, one cannot depend on these living families for answers.
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