ratites
Examples
A third rarer type of feather, the filoplume, is hairlike and (if present in a bird; they are entirely absent in ratites citation ) grows along the fluffy down feathers.
However, the classification of the ratites as a single order has always been questioned, with the alternative classification restricting the Struthioniformes to the ostrich lineage and elevating the other groups.
Illustration of cassowary skull The evolutionary history of cassowaries, as of all ratites, is not well known.
In the Berlin specimen, there are "trousers" of well-developed feathers on the legs; some of these feathers seem to have a basic contour feather structure, but are somewhat decomposed (they lack barbicels as in ratites ).
It is the only structure found in primitive birds such as ratites.
Like most other ratites, they have no uropygial gland (preen gland).