Editing Pennaceous feather (section)

== Description ==
A pennaceous [[feather]] has a stalk or quill.<ref name=":0">{{Cite web|title = Feather evolution|url = http://people.eku.edu/ritchisong/feather_evolution.htm|website = people.eku.edu|access-date = 2015-06-01|archive-url = https://web.archive.org/web/20170225102837/http://people.eku.edu/ritchisong/feather_evolution.htm|archive-date = 2017-02-25|url-status = dead}}</ref> Its basal part, called a ''calamus'', is embedded in the skin. The calamus is hollow and has pith formed from the dry remains of the feather pulp, and the calamus opens below by an ''inferior umbilicus'' and above by a ''superior umbilicus''.<ref name=":0" /> The stalk above the calamus is a solid ''[[rachis]]'' having an umbilical groove on its underside. Pennaceous feathers have a rachis with ''vanes'' or  ''vaxillum '' spreading to either side. These vanes are composed of a high number of flattened ''[[Barb (feather)|barb]]s'', that are connected to one another with ''[[barbule]]s''.

The barbules are tiny strands that criss-cross on the flattened sides of the barbs. This forms a miniature [[velcro]]-like mesh that holds all the barbs together, stabilizing the vanes.<ref>{{cite journal | doi=10.1098/rsif.2013.0988 | title=Unzipping bird feathers | date=2014 | last1=Kovalev | first1=Alexander | last2=Filippov | first2=Alexander E. | last3=Gorb | first3=Stanislav N. | journal=Journal of the Royal Society Interface | volume=11 | issue=92 | pmid=24352674 | pmc=3899865 }}</ref>

Pennaceous feathers on the wing, and elsewhere, where stresses related to flight, or other activities, are high, are accordingly attached especially strongly. This strong attachment is accomplished by ligaments under the skin, which in some birds and other [[feathered dinosaurs]] results in raised bumps or marks along the rear forelimb bone ([[ulna]]). These bumps, called quill knobs (ulnar papillae), are often used as an indirect indication of strongly-attached forelimb feathers in [[fossil]] species, and can also indirectly indicate the number of secondary [[flight feathers]] in a given specimen.<ref name="turneretal2007b">{{cite journal |last=Turner |first=A.H. |author2=Makovicky, P.J. |author3=Norell, M.A.  |year=2007 |title=Feather quill knobs in the dinosaur ''Velociraptor'' |journal=Science |volume=317 |issue=5845 |page=1721|doi=10.1126/science.1145076 |pmid=17885130 |bibcode = 2007Sci...317.1721T |doi-access=free }}</ref><ref>{{Cite journal | last1 = Zelenitsky | first1 = D. K. | last2 = Therrien | first2 = F. | last3 = Erickson | first3 = G. M. | last4 = Debuhr | first4 = C. L. | last5 = Kobayashi | first5 = Y. | last6 = Eberth | first6 = D. A. | last7 = Hadfield | first7 = F. | doi = 10.1126/science.1225376 | title = Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins | journal = Science | volume = 338 | issue = 6106 | pages = 510–514 | year = 2012 | pmid =  23112330| bibcode = 2012Sci...338..510Z | s2cid = 2057698 }}</ref>

[[Flight feather]]s ([[remiges]] and [[rectrices]]) are specialized types of pennaceous feathers, [[adaptation|adapted]] for high [[wing loading|loading]]s and often strongly asymmetric for improved [[bird flight|flight]] performance.