| Avifilopluma | |
|---|---|
 | |
| Illustration showing various types offeathers | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Avemetatarsalia |
| Clade: | Avifilopluma Gauthier &de Queiroz, 2001 |
| Subgroups | |
Also see text. | |
| Synonyms | |
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Avifilopluma ("bird filoplumes") is aclade containing all animals withfeathers. Unlike most clades, which are defined based on relative relationships, Avifilopluma is defined based on anapomorphy, that is, a unique physical characteristic shared by one group and not found outside that group (in this case, feathers). Its content is unclear, and has been speculated to range fromCoelurosauria to all ofOrnithodira.
The clade Avifilopluma was created along with several other apomorphy-based clades relating tobirds byJacques Gauthier andKevin de Queiroz in a 2001 paper. Their specific definition for the group was "the clade stemming from the firstpan-avian with feathershomologous (synapomorphic) with those ofAves (Vultur gryphus Linnaeus 1758)."[1]
The authors went on to define specifically what qualified as a "feather": Any filamentous structure arising from a follicle in the skin, with a hollow base, that shares common ancestry with the feathers of modern birds.[1]
Gauthier and de Queiroz originally referred a number of prehistoric species to this group, on the basis of fossilized feather traces. These included what they considered to be non-aviandinosaurs such asSinornithosaurus,Archaeopteryx, and theenantiornithines, all of which had true feathers. They tentatively considered the simpler feathers of other dinosaurs likeSinosauropteryx andBeipiaosaurus to be homologues of modern feathers and thus probably included in Avifilopluma. Therefore, they concluded that Avifilopluma would include most of the cladeManiraptora orCoelurosauria.[1]
The authors went further, and speculated that pending more complete knowledge of dinosaur skin structures, even the most primitivetheropods could turn out to be avifiloplumans.[1] This idea gained tentative support with the discovery ofTianyulong, anornithischian dinosaur with apparently hollow, filamentous feather-like fibers covering its body. This specimen was described by Zheng and colleagues in 2009, who noted definite similarities between the filaments ofTianyulong and coelurosaurian theropods, supporting the idea that all such structures were homologous with modern feathers, and pushing the origin of feathers back to the origin of dinosaurs or earlier.[2] The discovery ofKulindadromeus supported the idea that feathers were already present in the last common ancestor of ornithischians and theropods, which was either the first dinosaur or the firstornithoscelidan depending on how ornithischians are related to other dinosaurs.[3][4]
Some scientists have gone even further and suggested that the downy filaments present inpterosaurs are also feathers, and if this is the case, it would place the origin of feathers at or before the primitive split between dinosaurs and pterosaurs (Ornithodira).[5][6]
