The Palaeognathae meaning ancient jaw) are the largest living birds, and are mostly flightless (but not all flightless are Palaeognathae, and not all Palaeognathae are large). They include the ostrich, emu, kiwi, etc. Palaeognathae are generally fast runners and use kicking as a primary defense. Palaeognaths probably evolved from early Cenozoic fly...