Avifilopluma
Encyclopedia
Avifilopluma is a clade
containing all animals with feather
s. Unlike most clades, which are defined based on relative relationships, Avifilopluma 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, feathers).
s 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 feathers homologous
(synapomorphic) with those of Aves (Vultur gryphus Linnaeus 1758)."
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.
s such as Sinornithosaurus
, Archaeopteryx
, and the enantiornithines
, all of which had true feathers. They tentatively considered the simpler feathers of other dinosaurs like Sinosauropteryx
and Beipiaosaurus
to be homologues of modern feathers and thus probably included in Avifilopluma. Therefore, they concluded that Avifilopluma would include most of the clade Maniraptora
or Coelurosauria
.
The authors went further, and speculated that pending more complete knowledge of dinosaur skin structures, even the most primitive theropods
could turn out to be avifiloplumans. This idea gained tentative support with the discovery of Tianyulong
, an ornithischia
n 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 of Tianyulong 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.
Some scientists have gone even further and suggested that the downy filaments present in some species of pterosaur
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).
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 animals with 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. Unlike most clades, which are defined based on relative relationships, Avifilopluma 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, feathers).
Definition
The clade Avifilopluma was created along with several other apomorphy-based clades relating to birdBird
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 feathers homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
(synapomorphic) with those of Aves (Vultur gryphus Linnaeus 1758)."
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.
Content
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-avian dinosaurDinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s such as Sinornithosaurus
Sinornithosaurus
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999...
, Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, and the enantiornithines
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
, all of which had true feathers. They tentatively considered the simpler feathers of other dinosaurs like Sinosauropteryx
Sinosauropteryx
Sinosauropteryx was the first genus of dinosaur outside of Avialae to be found with evidence of feathers. They were covered with "furry" coats of very simple filament-like feathers...
and Beipiaosaurus
Beipiaosaurus
Beipiaosaurus is a genus of therizinosauroid theropod dinosaur from the Early Cretaceous of China.The exact classification of therizinosaurs had in the past been hotly debated, since their prosauropod-like teeth and body structure indicate that they were generally herbivorous, unlike typical...
to be homologues of modern feathers and thus probably included in Avifilopluma. Therefore, they concluded that Avifilopluma would include most of the clade Maniraptora
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...
or Coelurosauria
Coelurosauria
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...
.
The authors went further, and speculated that pending more complete knowledge of dinosaur skin structures, even the most primitive theropods
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
could turn out to be avifiloplumans. This idea gained tentative support with the discovery of Tianyulong
Tianyulong
Tianyulong is a genus of heterodontosaurid ornithischian dinosaur. The only species is T. confuciusi, whose remains were discovered in Jianchang County, Western Liaoning Province, China...
, an ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n 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 of Tianyulong 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.
Some scientists have gone even further and suggested that the downy filaments present in some species of pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
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).