Birds evolved from a group of small predatory dinosaurs in the Jurassic period, 155 million years ago. The most famous extinct bird is also the earliest known bird, Archaeopteryx. The first complete specimen was found in southern Germany in 1861. The fossil, which was about 0.5 m (1.6 ft) in length, has features intermediate between theropod dinosaurs and modern birds, a prime example of a transitional fossil. For instance, it was covered in feathers, had broad wings, and the ability to fly, but its skeletal structure was more like that of a dinosaur, and included a "killing claw" on its legs. The existence of Archaeopteryx helped support Darwin's arguments for evolution and natural selection at a crucial time.
Another famous type of extinct bird were the ratites, large flightless birds that live in South America, Africa, and Australia. Ratites are flightless birds with a similar body type, represented today by ostriches, emus, rheas, kiwis, cassowaries, and the tinamous. The African Ostrich is the largest living bird, with the tallest members of the species reaching 3.3 m (10 ft) in height and 154 kg (340 lb) in weight.
Some extinct ratites were even larger, reaching heights of 3.6 m (12 ft) in the case of the Giant Moa, which lived in New Zealand up until the 1500s, and weights of up to half a ton (454 kg or 1,000 lb) in the case of the Elephant Bird, an extinct bird which lived in Madagascar up until the 1500s. The Elephant Bird is the largest bird that ever lived, and really was almost as tall as an elephant.
Another category of extinct bird, the phorusrhacids, or "Terror Birds," were dominant predators in South America for over 60 million years, from just after the extinction of the dinosaurs 65 million years ago, all the way up until 1.8 million years ago, when they went extinct, probably due to competition from mammals coming over the Panama Isthmus from North America. The Terror Birds were up to 3.3 m (10 ft) in height, with skulls as long as 0.7 m (2 ft). These massive skulls could have been used to kill numerous mammals found in South America at the time with just a single blow. Terror Birds are the one category of extinct bird which we can be most thankful is extinct.