hypoptilum

From the New Latin hypoptila .

hypoptilum (plural hypoptila)

1. (ornithology, rare) An aftershaft.
   • 1924 October 30, W. DeW. Miller, “Variations in the structure of the aftershaft and their taxonomic value”, in American Museum Novitates, number 140:

     This secondary feather is known as the aftershaft or hypoptilum, and its presence or absence constitutes the most important structural difference in the feathers of existing birds.

   • 2016, Michael Heads, Biogeography and Evolution in New Zealand:

     The feathers in some ratites are unusual as they are less reduced than is the norm in birds—each feather has, in addition to the main feather, a large “after-shaft” or hypoptilum.