the terminal part of a bird's wing corresponding to the thumb, consisting of two or more quills; bastard wing
Origin:
ModL, dim of ala, wing: see aileron
See alula in American Heritage Dictionary 4
nounpl.al·u·lae(-lēˌ)
A small joint in the middle of a bird's wing, homologous with the thumb and bearing three or four quill-like feathers. Also called bastard wing, spurious wing.