Pennaceous feather Pennaceous feather 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
Rachis achieved pachytene and are attached to the walls of the gonadal tube. The rachis is filled with cytoplasm. In plants, a "rachis" is the main axis of a compound structure. It can be the main stem of a compound leaf, such as in "Acacia" or ferns, or the main, flower-bearing portion of an inflorescence above a supporting peduncle. A ripe head of wild-type wheat is easily shattered into dispersal units when touched or blown by the wind. A series of layers forms that divides the rachis into dispersal units consisting of a small group of flowers (a single spikelet) attached