Bats

Bats are one of the most diverse and widely distributed groups of mammals on Earth, second only to rodents in the number of species. More than 900 species of bats have been described. They occur in most terrestrial biomes, except for the high Arctic and all of Antarctica. Bats are the only truly flying mammals, and are distinct from the flying lemurs and flying squirrels, which actually glide. Bats make up the order Chiroptera, named from the Greek words cheir (hand) and pteron (wing); this is an appropriate name, since the wing is formed by modified bones of the hand.

The bat order Chiroptera is divided into two suborders. The Megachiroptera is composed of a single family that is restricted to the tropics, and includes the largest species of bats, such as fruit bats and flying foxes. The megachiropterans are characterized by large eyes, simple ears, and a dog-like face. The Microchiroptera are made up of 17 families, and feature small eyes, complex ears, and an ability to find their prey and navigate by echolocation. Certain differences between the two suborders in flight and sensory capabilities have led some biologists to propose that they evolved from separate ancestral lineages, and that the megachiropteran bats are more closely related to primates. This idea is highly controversial, however, and other morphological data and DNA evidence support the hypothesis that all of the bats evolved from a common ancestor. Most bat scientists believe that bats evolved from tree-dwelling, shrew-like ancestors that scampered along branches and fed on insects. The proto-bat likely had long fingers supporting webs of skin attached to the body, which it used to glide while in pursuit of its insect prey.