Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger.

Traditionally, pterosaurs were divided into two major types. Basal pterosaurs (also called non-pterodactyloid pterosaurs or 'rhamphorhynchoids') were smaller animals, with up to a wingspan, fully toothed jaws and, typically, long tails. Their wide wing membranes probably included and connected the hindlimbs.