al·u·la 
(ălyə-lə)
(ălyə-lə)n. pl. al·u·lae (-lē′)
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.
[New Latin, diminutive of Latin āla, wing.]
alu·lar (-lər) adj.