Aviremigia

Aviremigia ("bird remiges") is a clade containing all bird-line archosaurs with pennaceous feathers, those with plumes or vanes running the length of a central quill, on their forelimbs (remiges) and tail (rectrices). Unlike most clades, which are defined based on relative relationships, Aviremigia is defined based on an apomorphy, that is, a unique physical characteristic shared by one group and not found outside that group (in this case, vaned wing and tail feathers).

Definition
The clade Aviremigia was created along with several other apomorphy-based clades relating to birds by Jacques Gauthier and Kevin de Queiroz in a 2001 paper. Their specific definition for the group was "the clade stemming from the first panavian with ... remiges and rectrices, that is, enlarged, stiff-shafted, closed-vaned (= barbules bearing hooked distal pennulae), pennaceous feathers arising from the distal forelimbs and tail"

Currently, the most primitive known theropod dinosaur species with feathers of this type is the basal maniraptoran Yixianosaurus longimanus. The earliest known definitive member of this clade is Anchiornis, from the middle Jurassic period of China, about 164 million years ago.

Another clade named by Gauthier and de Queiroz in the same paper, Avipinna (defined as all panavians with pennaceous feathers anywhere on the body), currently has the same content as Aviremigia.