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Epidexipteryx
Fossil range: Late Jurassic, 152 Mya
Epidexipteryx BW
Scientific classification

Class

Reptilia

Superorder

Dinosauria

Order

Saurischia

Suborder

Theropoda

Family (Unranked)

Coelurosauria

Family

Scansoriopterygidae

Genus

Epidexipteryx
Zhang et al., 2008

Species


Epidexipteryx ("display feather") is a genus of small maniraptoran dinosaur, known from one fossil specimen in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. Epidexipteryx represents the earliest known example of ornamental feathers in the fossil record.[1] The type specimen is catalog number IVPP V 15471. It has been reported to be a maniraptoran dinosaur from the Middle Jurassic or Upper Jurassic age Daohugou Beds of Inner Mongolia, China (about 152 to 168 mya).[2]

The specific name, Epidexipteryx hui ("Hu's display feather"), and its Chinese name Hushiyaolong ("Hu Yaoming's dragon") were coined in memory of paleomammologist Hu Yaoming.[3]

Epidexipteryx's skull is short-snouted with a truncated antorbital fenestra, a nostril positioned in a relatively high position, and strongly procumbent, proportionally large anterior teeth (the teeth get smaller further back). Its arms and hands were very elongate as well.

DescriptionEdit

It is known from a well preserved partial skeleton that includes four long feathers on the tail, composed of a central rachis 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."[2]

In all, the skeleton of Epidexipteryx hui measures 25 centimeters (10 inches) in length (44.5 cm or 17.5 in including the incomplete tail feathers),[4] and the authors estimated a weight of 164 grams, smaller than most other basal avialans.[2]

SkullEdit

Epidexipteryx 300 400

Artist's rendition, clearly showing the tail feathers.

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.

Non-tail feathersEdit

The non 'ETF's appear like flattened, closed flowers with their petals pointing upwards in parallel fashion. The 'non-ETFs' have their distal parts composed of filamentous parallel barbs, and they emerge from a membranous base. Epidexipteryx was hence covered in complex, filamentous structures.

Relationship with birdsEdit

The rest of the skeleton bore an overall similarity to the closely related Epidendrosaurus, including a hip configuration unusual among other dinosaurs: the pubis was shorter than the ischium, and the ischium itself was expanded towards the tip. However, the tail of Epidexipteryx differed significantly from Epidendrosaurus. In Epidendrosaurus, the tail was long, about 300% of total trunk length, while the short tail of Epidexipteryx was only 70% of its trunk length. The tail of Epidexipteryx also bore unusual vertebrae towards the tip which resembled the feather-anchoring pygostyle of modern birds and some oviraptorosaurs.[2]

Epidexipteryx also shares many derived features with modern birds, including a humerus the same length as its femur.[2]

Despite its close relationship to avialan birds, Epidexipteryx appears to have lacked remiges (wing feathers), and it likely could not fly. Zhang et al. suggest that unless Epidexipteryx evolved from flying ancestors and subsequently lost its wings, this may indicate that advanced display feathers on the tail may have predated flying or gliding flight.[2]

Tail structuresEdit

The holotype preserves four super-long, strap-like structures growing from its distal-most ten tail vertebrae (these are termed ETFs by the authors, for Elongate ribbon-like Tail Feathers). These structures are likely to have played a role in display (Zhang et al. 2008), and if they're homologous with feathers (which is likely), then here is possible evidence that feathers initially evolved for display (unlike birds and other feathered maniraptorans, Epidexipteryx does not have complex feathers on its arms).[2]

Epidexipteryx is the oldest and most phylogenetically basal theropod known to display feathers, suggesting that display feathers appeared before flight feathers and flight ability in basal avialans.[2]

History of publicationEdit

Due to a pre-publication error,[5] 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 23rd, 2008 issue of the journal Nature.[2]

ReferencesEdit

  1. ^ Morgan, James (2008-10-22). "New feathered dinosaur discovered". BBC. http://news.bbc.co.uk/2/hi/science/nature/7684796.stm. Retrieved on 2009-07-02. 
  2. ^ a b c d e f g h i Zhang, Fucheng; Zhou, Zhonghe; Xu, Xing; Wang, Xiaolin and Sullivan, Corwin. "A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers". <http://www.nature.com/nature/journal/v455/n7216/full/nature07447.html> Nature 455, 1105-1108 (23 October 2008) | doi:10.1038/nature07447
  3. ^ "Chinese scientists discovers new dinosaur species". People's Daily Online. 15:26, October 27, 2008. http://english.people.com.cn/90001/90776/90881/6522141.html. Retrieved on November 4, 2008. 
  4. ^ Zhang, F., Zhou, Z., Xu, X., Wang, X. and Sullivan, C. (2008). "A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers", Supplementary Informtion. Nature, 455: 46pp. doi: 10.1038/nature07447
  5. ^ Dr. Thomas Holtz, Jr. "The mistaken scansoripterygid". Message to the Dinosaur Mailing List <http://dml.cmnh.org/2008Oct/msg00008.html> (October 1, 2008)


External linksEdit

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