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Jennifer_P wrote:Finally the sandpiper lost its ability to fly altogether, and thereafter it began rapidly changing its now-useless wings into true arms that it held in front of its body. At the same time, the melded bones of the wing began to split out into individual fingers. Furthermore, to balance the extra weight of having its arms out front instead of tucked to the sides, its tail lengthened and grew heavier.
A recently discovered species, 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 28-inch (71 cm), nearly intact skull. The beak is roughly 18 inches (460 mm) long and curves in a hook shape that resembles an eagle's beak. It is thought that this new species would easily be able to swallow dog-sized prey. Most species described as Phorusrhacidae birds were smaller, 2 to 3 feet (0.6 - 0.9m) tall, but the new fossil belongs to a bird that probably stood about 10 feet (3.0 m) tall (3 m). Although scientists cannot be sure, they predict that the large terror birds were extremely nimble and quick runners able to reach speeds of 30 mph (48 km/h).
Phorusrhacids are colloquially known as "terror birds", because their larger species were apex predators and the most fearsome carnivores of their habitat (before, during and after the arrival of saber-toothed cats 2.5 Ma ago). Their wings had evolved into meathook-like structures that likely could be stretched out like arms to perform a hacking motion which theoretically would help in bringing down prey. Most of the smaller and some of the larger species are believed to have been fast runners.
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