Definition from Wiktionary, the free dictionary
hypoptilum (plural hypoptila)
- (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.
aftershaft — see aftershaft