Non-downy feather with vanes composed of many interlocking barbules
The
rectrix and
remex seen above are two examples of pennaceous feathers.
An
ostrich down feather is an example of a
plumulaceous feather. Its rudimentary rhachis with long flexible barbs and elongate barbules cannot form vanes.
The pennaceous feather is a type of feather present in most modern birds and in some other species of maniraptoriform dinosaurs.[1]