Pyrenean ostrich differs from the ancestor in more thickset constitution – it is an adaptation to reduction of heat emitting in winter. Growth of an adult bird is up to 1.5 m; weight is about 110 kg. This ostrich has heavier constitution comparatively to ancestor: short thick neck and thick legs. Head of this species also seems larger and more massive. The lateral toe on legs is reduced in great degree, almost useless and only slightly touches the ground. Despite of this feature, characteristic for quickly running birds, Pyrenean ostrich can accelerate momentum only about 50 kms per hour. Possible, it descends from quickly running ancestors, but has lost a part of speed due to development of northern habitats of colder climate.