pin·nule 
(pĭnyl) also pin·nu·la (pĭnyə-lə)
(pĭnyl) also pin·nu·la (pĭnyə-lə)n. pl. pin·nules also pin·nu·lae (pĭnyə-lē′)
1. Botany One of the secondary divisions of a binnately compound leaf.
2. Zoology A small featherlike part or subdivision of an appendage, especially one of the small branches on the arm of a crinoid.
[Latin pinnula, diminutive of pinna, feather; see pet- in the Appendix of Indo-European roots.]
pinnu·lar adj.