The
pennaceous feather is a type of
feather present in most modern
birds and in some other species of
maniraptoriform dinosaurs. A pennaceous feather has a stalk or quill. 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. 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
barbs, that are connected to one another with
barbules.