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''Epidexipteryx'' is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of small paravian dinosaurs, known from one fossil specimen in the collection of the
Institute of Vertebrate Paleontology and Paleoanthropology The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name sugges ...
in
Beijing } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...
. ''Epidexipteryx'' represents the earliest known example of ornamental feathers in the fossil record.


Discovery

The
type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...
is catalog number IVPP V 15471. The specific name, ''Epidexipteryx hui'' ("Hu's display feather"), and its Chinese name ''Hushi Yaolong'' ("Hu Yaoming's dragon") were coined in memory of paleomammologist
Hu Yaoming HU or Hu may refer to: Arts and entertainment * Hu Sanniang, a fictional character in the ''Water Margin'', one of the Four Great Classical Novels of Chinese literature * Tian Hu, one of the antagonists in the ''Water Margin'' * Hollywood Un ...
. Due to a pre-publication error,Dr. Thomas Holtz, Jr. "The mistaken scansoripterygid". Message to the Dinosaur Mailing List (October 1, 2008) a manuscript of the ''Epidexipteryx hui'' description first appeared on a preprint Web portal in late September 2008. The paper was officially published in the October 23, 2008 issue of the journal ''Nature''.


Description

''E. hui'' is known from a well-preserved partial skeleton that includes four long feathers on the tail, composed of a central
rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...
and vanes. However, unlike in modern-style rectrices (tail feathers), the vanes were not branched into individual filaments but made up of a single ribbon-like sheet. ''Epidexipteryx'' also preserved a covering of simpler body feathers, composed of parallel barbs as in more primitive feathered dinosaurs. However, the body feathers of ''Epidexipteryx'' are unique in that some appear to arise from a "membranous structure" at the base of each feather. It has been suggested that this may represent a stage in the evolution of the feather. In all, the skeleton of ''Epidexipteryx hui'' measures in length ( including the incomplete tail feathers), and the authors estimated a weight of 164 grams, smaller than most other basal avialans. Gregory S. Paul presented a length estimate of and body mass estimte of . The skull of ''Epidexipteryx'' is also unique in a number of features, and bears an overall similarity to the skull of '' Sapeornis'', oviraptorosaurs and, to a lesser extent, therizinosauroids. It had teeth only in the front of the jaws, with unusually long front teeth angled forward, a feature only seen in '' Masiakasaurus'' among other theropods. The rest of the skeleton bore an overall similarity to the possibly closely related '' Scansoriopteryx'', including a hip configuration unusual among other dinosaurs: the pubis was shorter than the
ischium The ischium () form ...
, and the ischium itself was expanded towards the tip. The tail of ''Epidexipteryx'' also bore unusual vertebrae towards the tip which resembled the feather-anchoring
pygostyle Pygostyle describes a skeletal condition in which the final few caudal vertebrae are fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these. The pygostyle is the main compo ...
of modern birds and some oviraptorosaurs.


Classification

The exact phylogenetic position of ''Epidexipteryx'' within Paraves is uncertain. The phylogenetic analysis conducted by the authors of its description recovered it as a member of the family Scansoriopterygidae and as a basal member of the clade
Avialae Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally use ...
; this was confirmed by the subsequent analysis conducted by Hu ''et al.'' (2009). A later analysis conducted by Agnolín and Novas (2011) confirmed it to be a scansoriopterygid, but recovered a different phylogenetic position of this family: Scansoriopterygidae was recovered in polytomy with the family Alvarezsauridae and the clade Eumaniraptora (containing the clades Avialae and Deinonychosauria). Turner, Makovicky and Norell (2012) included ''Epidexipteryx'' but not ''Scansoriopteryx''/''Epidendrosaurus'' in their primary phylogenetic analysis, as a full-grown specimen is known only of the former taxon; regarding ''Scansoriopteryx''/''Epidendrosaurus'', the authors were worried that including it in the primary analysis would be problematic, because it is only known from juvenile specimens, which "do not necessarily preserve all the adult morphology needed to accurately place a taxon phylogenetically" (Turner, Makovicky and Norell 2012, p. 89). ''Epidexipteryx'' was recovered as basal paravian that didn't belong to Eumaniraptora. The authors did note that its phylogenetic position is unstable; constraining ''Epidexipteryx hui'' as a basal avialan required two additional steps compared to the most parsimonious solution, while constraining it as a basal member of Oviraptorosauria required only one additional step. A separate exploratory analysis included ''Scansoriopteryx''/''Epidendrosaurus'', which was recovered as a basal member of Avialae; the authors noted that it did not clade with ''Epidexipteryx'', which stayed outside Eumaniraptora. Constraining the monophyly of Scansoriopterygidae required four additional steps and moved ''Epidexipteryx'' into Avialae. A monophyletic Scansoriopterygidae was recovered by Godefroit ''et al.'' (2013); the authors found scansoriopterygids to be basalmost members of Paraves and the sister group to the clade containing Avialae and Deinonychosauria. Agnolín and Novas (2013) recovered monophyletic Scansoriopterygidae as well, but found them to be non-paravian maniraptorans and the sister group to Oviraptorosauria. An abbreviated version of Zhang ''et al.s 2008
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
is presented below.


Paleobiology

''Epidexipteryx'' appears to have lacked remiges (wing feathers), though based on the related '' Yi'', it may have possessed some sort of membrane wing to allow gliding.Cau, A (2012)
Il ritorno del paraviano pterosauro-mimo?
Theropoda, July 2012


Paleoenvironment

''Epidexipteryx'' is known from the
Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations ...
or
Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...
age
Daohugou Beds The Haifanggou Formation (), also known as the Jiulongshan Formation (), is a fossil-bearing rock deposit located near Daohugou () village of Ningcheng County, in Inner Mongolia, northeastern China. The formation consists of coarse conglomerate ...
of
Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for ...
, China (about 160 or 154
mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...
).


References


External links


New feathered dinosaur discovered
''
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'' {{Taxonbar, from=Q132600 Prehistoric paravians Jurassic dinosaurs of Asia Fossil taxa described in 2008 Feathered dinosaurs