Cephalometric correlates of echolocation in the chiroptera.

This study suggests that the evolution of head posture in bats is constrained by the demands of vocalization during echolocation. Nasal-emitting microchiropteran taxa are easily identified by their characteristic rotation of the basicranium ventrally about the cervical axis, the depression of the rostrum below the basicranial axis, and by the rotation of the lateral semicircular canals so as to maintain their horizontal orientation during flight. The converse is true for oral-emitting Microchiroptera. The general form of the microchiropteran skull has been canalized along two distinct evolutionary paths, respectively, towards oral-emitting or nasal-emitting forms.