The taxonomic distribution of widened and/or pronged hamuli (hooklets) on distal barbules in the pennaceous part of feathers was studied with light microscopy (LM) and scanning electron microscopy (SEM) in order to assess the diagnostic and phylogenetic significance of these structures. Comparison of the LM and SEM appearance of these structures indicates that "thickened" hamuli are artifacts, arising from the misinterpretation of rotated tape-like structures. Pronged hamuli, on the contrary, are non-artifacts. These structures have a much wider taxonomic distribution than was reported by earlier workers, and therefore do not seem to be useful for identifying feather fragments.
Brom, Tim G. and Frank, Uri
"The Diagnostic and Phylogenetic Significance of Widened and Pronged Hamuli in Feathers,"
Scanning Microscopy: Vol. 6
, Article 24.
Available at: https://digitalcommons.usu.edu/microscopy/vol6/iss2/24