Aviremigia is a clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 containing all bird-line archosaurs with pennaceous feather

Feather

Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

s, 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 bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s by Jacques Gauthier

Jacques Gauthier

Jacques Armand Gauthier is a vertebrate paleontologist, comparative morphologist, and systematist, and one of the founders of the use of cladistics in biology....

 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 with feathers of this type is the basal oviraptorosaur Protarchaeopteryx

Protarchaeopteryx

Protarchaeopteryx is a genus of turkey-sized feathered theropod dinosaur from China. Known from the Jianshangou bed of the Yixian Formation, it lived during the early Aptian age of the Early Cretaceous, approximately 124.6 million years ago...

. The earliest known definitive member of this clade is Anchiornis

Anchiornis

Anchiornis is a genus of small, feathered, deinonychosaurian dinosaur. The genus Anchiornis contains the type species Anchiornis huxleyi, named in honor of Thomas Henry Huxley, an early proponent of biological evolution, and the first to propose a close evolutionary relationship between birds and...

, from the middle Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 period of China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, 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.