Hot deserts are found along the latitudes of the tropics, where air that has risen and lost its moisture at the Equator descends and settles dryly over the land. In Africa the deserts are found in the southwestern corner of the continent, and all across the north. The northern Sahara Desert is so vast and inhospitable that it provides the boundary between the Afrotropical and the Palaearctic ecozones. Nevertheless, despite the harsh conditions, there are some animals that do live here. Small, non-avian coelurosaurs have proved to be adaptable enough to develop forms that are uniquely suited to such an environment; forms such as the sandle and the wyrm.
The days are so hot and the nights so cold that any animal must spend much of its time protected from the extremes. The sandle does this by burrowing in the sand. Its streamlined spindle shape is ideal for a burrowing way of life, since sand grains slide past its smooth contours easily as it tunnels through the dunes, digging and pushing with its stumpy legs. The eyes and nostrils are high up on the head, enabling it to see about and breathe while the rest of the body is buried. Desert animals need to be very careful about water conservation. The sandle never drinks but obtains water from the moist flesh of the prey animals it eats. Its kidneys are very efficient, allowing almost all the moisture to be retained, and secreting any poisonous compounds in a saliva that helps to paralyze and subdue its prey.