Definition of "pinnule" []

• Botany Any of the ultimate leaflets of a bipinnately compound leaf. (noun)
• Zoology A featherlike or plumelike organ or part, such as a small fin, or one of the appendages of a crinoid. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Conrad Labandeira himself talks about this in a 1998 review paper, in which he describes: “spore feeding and piercing-and sucking” [in the early Devonian], “External feeding on pinnule margins and the intimate and intricate association of galling” [in the Carboniferous], “hole feeding and skeletonization” [in the early Permian], “surface fluid feeding”, and possible but inconclusive evidence of “mutualistic relationships between insect pollinivores and seed plants” by the end of the Paleozoic."
• "At the end of each of the small divisions of the compound leaflet there is, when the leaf first unfolds, a little yellow fruit-like body united by a point at its base to the end of the pinnule."
• "[Illustration] (2) Sporangia in oblong sori under a reflexed tooth of a pinnule; indusium broad; rachis dark and shining."