Feathered dinosaur
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/3f/Anchiornis_martyniuk.png/220px-Anchiornis_martyniuk.png)
The realization that dinosaurs are closely related to birds raised the obvious possibility of feathered dinosaurs. Fossils of Archaeopteryx include well-preserved feathers, but it was not until the early 1990s that clearly non-avian dinosaur fossils were discovered with preserved feathers. Today more than twenty genera of dinosaurs, mostly theropods, are known to have been feathered. Most fossils are from the Yixian formation in China. The fossil feathers of one specimen, Shuvuuia deserti, have tested positive for beta-keratin, the main protein in bird feathers, in immunological tests.[1]
Early hypotheses
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Archaeopteryx_lithographica_%28Berlin_specimen%29.jpg/220px-Archaeopteryx_lithographica_%28Berlin_specimen%29.jpg)
Shortly after the 1859 publication of Charles Darwin's On the Origin of Species, British biologist and evolution-defender Thomas Henry Huxley proposed that birds were descendants of dinosaurs. He compared the skeletal structure of Compsognathus, a small theropod dinosaur, and the 'first bird' Archaeopteryx lithographica (both of which were found in the Upper Jurassic Bavarian limestone of Solnhofen). He showed that, apart from its hands and feathers, Archaeopteryx was quite similar to Compsognathus. In 1868 he published On the Animals which are most nearly intermediate between Birds and Reptiles, making the case.[2][3] The leading dinosaur expert of the time, Richard Owen, disagreed, claiming Archaeopteryx as the first bird outside dinosaur lineage. For the next century, claims that birds were dinosaur descendants faded, with more popular bird-ancestry hypotheses including 'crocodylomorph' and 'thecodont' ancestors, rather than dinosaurs or other archosaurs.
In 1964, John Ostrom described Deinonychus antirrhopus, a theropod whose skeletal resemblance to birds seemed unmistakable. Ostrom became a leading proponent of the theory that birds are direct descendants of dinosaurs. Further comparisons of bird and dinosaur skeletons, as well as cladistic analysis strengthened the case for the link, particularly for a branch of theropods called maniraptors. Skeletal similarities include the neck, the pubis, the wrists (semi-lunate carpal), the 'arms' and pectoral girdle, the shoulder blade, the clavicle and the breast bone. In all, over a hundred distinct anatomical features are shared by birds and theropod dinosaurs.
Other researchers drew on these shared features and other aspects of dinosaur biology and began to suggest that at least some theropod dinosaurs were feathered. The first restoration of a feathered dinosaur was Sarah Landry's depiction of a feathered "Syntarsus" (now renamed Megapnosaurus or considered a synonym of Coelophysis), in Robert T. Bakker's 1975 publication Dinosaur Renaissance.[4] Gregory S. Paul was probably the first paleoartist to depict maniraptoran dinosaurs with feathers and protofeathers, starting in the late 1970s.
By the 1990s, most paleontologists considered birds to be surviving dinosaurs and referred to 'non-avian dinosaurs' (all extinct), to distinguish them from birds (aves). Before the discovery of feathered dinosaurs, the evidence was limited to Huxley and Ostrom's comparative anatomy. Some mainstream ornithologists, including Smithsonian Institution curator Storrs L. Olson, disputed the links, specifically citing the lack of fossil evidence for feathered dinosaurs.
Fossil evidence
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Sinosauropteryxfossil.jpg/220px-Sinosauropteryxfossil.jpg)
After a century of hypotheses without conclusive evidence, especially well-preserved fossils of feathered dinosaurs were discovered during the 1990s, and more continue to be found. The fossils were preserved in a Lagerstätte — a sedimentary deposit exhibiting remarkable richness and completeness in its fossils — in Liaoning, China. The area had repeatedly been smothered in volcanic ash produced by eruptions in Inner Mongolia 124 million years ago, during the Early Cretaceous Period. The fine-grained ash preserved the living organisms that it buried in fine detail. The area was teeming with life, with millions of leaves, angiosperms (the oldest known), insects, fish, frogs, salamanders, mammals, turtles, lizards and crocodilians discovered to date.
The most important discoveries at Liaoning have been a host of feathered dinosaur fossils, with a steady stream of new finds filling in the picture of the dinosaur-bird connection and adding more to theories of the evolutionary development of feathers and flight. Norell et al. (2007) reported quill knobs from an ulna of Velociraptor mongoliensis, and these are strongly correlated with large and well-developed secondary feathers.[5]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Citipati_IGM_100_979.jpg/220px-Citipati_IGM_100_979.jpg)
Behavioural evidence, in the form of an oviraptorosaur on its nest, showed another link with birds. Its forearms were folded, like those of a bird. Although no feathers were preserved, it is likely that these would have been present to insulate eggs and juveniles.
Genuine feathers?
There have been claims that the supposed feathers of the Chinese fossils were a preservation artifact.[6] Despite doubts, the fossil feathers have roughly the same appearance as those of birds fossilized in the same locality, so there is no serious reason to think they are of different nature; moreover, no non-theropod fossil from the same site shows such an artifact, but sometimes show unambiguous hair (some mammals) or scales (some reptiles). [citation needed]
The "Archaeoraptor" fake
In 1999, a supposed 'missing link' fossil of an apparently feathered dinosaur named "Archaeoraptor liaoningensis", found in Liaoning Province, northeastern China, turned out to be a forgery. Comparing the photograph of the specimen with another find, Chinese paleontologist Xu Xing came to the conclusion that it was composed of two portions of different fossil animals. His claim made National Geographic review their research and they too came to the same conclusion.[7] The bottom portion of the "Archaeoraptor" composite came from a legitimate feathered dromaeosaurid now known as Microraptor, and the upper portion from a previously-known primitive bird called Yanornis.
Current knowledge
List of dinosaur genera preserved with evidence of feathers
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Sinornithosaurus_IVPP_V12811.jpg/220px-Sinornithosaurus_IVPP_V12811.jpg)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Sinornithosaurus_Dave_NGMC91.jpg/220px-Sinornithosaurus_Dave_NGMC91.jpg)
A number of non-avian dinosaurs are now known to have been feathered. Direct evidence of feathers exists for the following genera, listed in the order currently accepted evidence was first published. In all examples, the evidence described consists of feather impressions, except those marked with an asterisk (*), which denotes genera known to have had feathers based on skeletal or chemical evidence, such as the presence of quill knobs.
- Avimimus* (1987)[8][9]
- Sinosauropteryx (1996)[10]
- Protarchaeopteryx (1997)[11]
- Caudipteryx (1998)[12]
- Rahonavis* (1998)[13]
- Shuvuuia (1999)[1]
- Sinornithosaurus (1999)[14]
- Beipiaosaurus (1999)[15]
- Microraptor (2000)[16]
- Nomingia* (2000)[17]
- Cryptovolans (2002)[18]
- Scansoriopteryx (2002)[19]
- Epidendrosaurus (2002)[20]
- Psittacosaurus? (2002)[21]
- Yixianosaurus (2003)[22]
- Dilong (2004)[23]
- Pedopenna (2005)[24]
- Jinfengopteryx (2005)[25][26]
- Juravenator? (2006)[27]
- Sinocalliopteryx (2007)[28]
- Velociraptor* (2007)[5]
- Similicaudipteryx (2008)[29][30]
- Epidexipteryx (2008)[31]
- Anchiornis (2009)[32]
- Tianyulong? (2009)[33]
- Concavenator* (2010)[34]
- Note, filamentous structures in some ornithischian dinosaurs (Psittacosaurus, Tianyulong) and pterosaurs may or may not be homologous with the feathers and protofeathers of theropods.[33][35]
Primitive feather types
The evolution of feather structures is thought to have proceeded from simple hollow filaments through several stages of increasing complexity, ending with the large, deeply rooted, feathers with strong pens (rachis), barbs and barbules that birds display today.[36]
Some evidence suggests that the original function of simple feathers was insulation. In particular, preserved patches of skin in large, derived, tyrannosauroids show scutes, while those in smaller, more primitive, forms show feathers. This may indicate that the larger forms had complex skins, with both scutes and filaments, or that tyrannosauroids may be like rhinos and elephants, having filaments at birth and then losing them as they developed to maturity.[23] An adult Tyrannosaurus rex weighed about as much as an African Elephant. If large tyrannosauroids were endothermic, they would have needed to radiate heat efficiently, and feathers would have interfered with this.[37]
It is not known with certainty at what point in archosaur phylogeny the earliest simple “protofeathers” arose, or if they arose once or, independently, multiple times. Filamentous structures are clearly present in pterosaurs, and long, hollow quills have been reported in specimens of the ornithischian dinosaurs Psittacosaurus and Tianyulong.[21][33] In 2009 Xu et al. noted that the hollow, unbranched, stiff integumentary structures found on a specimen of Beipiaosaurus were strikingly similar to the integumentary structures of psittacosaurus and pterosaurs. They suggested that all of these structures may have been inherited from a common ancestor much earlier in the evolution of archosaurs, possibly in an ornithodire from the Middle Triassic or earlier.[38]
Display feathers are also known from dinosaurs that are very primitive members of the bird lineage, or Avialae. The most primitive example is Epidexipteryx, which had a short tail with extremely long, ribbon - like, feathers. Oddly enough, the fossil does not preserve wing feathers, suggesting that Epidexipteryx was either secondarily flightless, or that display feathers evolved before flight feathers in the bird lineage.[39]
Phylogeny and the inference of feathers in other dinosaurs
Fossil feather impressions are extremely rare and they require exceptional preservation conditions to form. Therefore only a few feathered dinosaur genera have been identified so far. However, through a process called phylogenetic bracketing, scientists can infer the presence of feathers on poorly-preserved specimens. All fossil feather specimens have been found to show certain similarities. Due to these similarities and through developmental research almost all scientists agree that feathers could only have evolved once in dinosaurs. Feathers would then have been passed down to all later, more derived species (although it is possible that some lineages lost feathers secondarily). If a dinosaur falls at a point on an evolutionary tree within the known feather-bearing lineages, scientists assume it too had feathers, unless conflicting evidence is found. This technique can also be used to infer the type of feathers a species may have had, since the developmental history of feathers is now reasonably well-known.[36]
The scientists who described the (apparently unfeathered) Juravenator performed a genealogical study of coelurosaurs, including distribution of various feather types. Based on the placement of feathered species in relation to those that have not been found with any type of skin impressions, they were able to infer the presence of feathers in certain dinosaur groups. The following simplified cladogram follows these results, and shows the likely distribution of plumaceous (downy) and pennaceous (vaned) feathers among theropods.[40] Note that the authors inferred pennaceous feathers for Velociraptor based on phylogenetic bracketing, a prediction later confirmed by fossil evidence.[5]
Coelurosauria |
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See also
References
- ^ a b Schweitzer, Mary Higby, Watt, J.A., Avci, R., Knapp, L., Chiappe, L, Norell, Mark A., Marshall, M. (1999). "Beta-Keratin Specific Immunological reactivity in Feather-like structures of the Cretaceous Alvarezsaurid, Shuvuuia deserti Journal of Experimental Zoology Part B (Mol Dev Evol) 285:146-157
- ^ Huxley, T.H. (1868). "On the animals which are most nearly intermediate between birds and reptiles". Annals and Magazine of Natural History. 2: 66–75.
- ^ Foster, Michael; Lankester, E. Ray 1898–1903. The scientific memoirs of Thomas Henry Huxley. 4 vols and supplement. London: Macmillan.
- ^ Paul, Gregory S. (2000). "A Quick History of Dinosaur Art". In Paul, Gregory S. (ed.) (ed.). The Scientific American Book of Dinosaurs. New York: St. Martin's Press. pp. 107–112. ISBN 0-312-26226-4.
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has generic name (help) - ^ a b c Turner, A.H. (2007). "Feather quill knobs in the dinosaur Velociraptor" (pdf). Science. 317 (5845): 1721. doi:10.1126/science.1145076. PMID 17885130.
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suggested) (help) - ^ Feduccia, A. Lingham-Soliar, T., and Hinchliffe, J.R. (2005). "Do feathered dinosaurs exist? Testing the hypothesis on neontological and paleontological evidence." Journal of Morphology, 266: 125-166.
- ^ "Transcript: The Dinosaur that Fooled the World". BBC. Retrieved 2006-12-22.
- ^ Kurzanov, S.M. (1987). "Avimimidae and the problem of the origin of birds." Transactions of the Joint Soviet-Mongolian Paleontological Expedition, 31: 5-92. [in Russian]
- ^ Chiappe, L.M. and Witmer, L.M. (2002). Mesozoic Birds: Above the Heads of Dinosaurs. Berkeley: University of California Press, 536 pp. ISBN 0-520-20094-2
- ^ Ji, Q., and Ji, S. (1996). "On discovery of the earliest bird fossil in China and the origin of birds." Chinese Geology 10 (233): 30-33.
- ^ Ji, Q., and Ji, S. (1997). "A Chinese archaeopterygian, Protarchaeopteryx gen. nov." Geological Science and Technology (Di Zhi Ke Ji), 238: 38-41. Translated By Will Downs Bilby Research Center Northern Arizona University January, 2001
- ^ Qiang, J., .Currie, P.J., Norell., M.A. & Shu-An, J., 1998. Two feathered dinosaursfrom northeastern China. Nature 393 753-761.
- ^ Forster, Catherine A. (1998a). "The Theropod Ancestry of Birds: New Evidence from the Late Cretaceous of Madagascar". Science (5358): pp. 1915–1919.
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suggested) (help). doi:10.1126/science.279.5358.1915 (HTML abstract) - ^ Xu, X., Wang, X., Wu, X., 1999. A dromaeosaurid dinosaur with a filamentous integument from the Yixian Formation of China. Nature 401:6750 262-266 doi 10.1038/45769
- ^ Xu. X., Zhao, X., Clark, J.M., 1999. A new therizinosaur from the Lower Jurassic lower Lufeng Formation of Yunnan, China. Journal of Vertebrate Paleontology 21:3 477–483 doi 10.1671/0272-4634
- ^ Xu, X., Zhou, Z., and Wang, X. (2000). "The smallest known non-avian theropod dinosaur." Nature, 408 (December): 705-708.[1]
- ^ Barsbold, R., Osmólska, H., Watabe, M., Currie, P.J., and Tsogtbaatar, K. (2000). "New Oviraptorosaur (Dinosauria, Theropoda) From Mongolia: The First Dinosaur With A Pygostyle". Acta Palaeontologica Polonica, 45(2): 97-106.
- ^ Czerkas, S.A., Zhang, D., Li, J., and Li, Y. (2002). "Flying Dromaeosaurs". In Czerkas, S.J. (ed.). Feathered Dinosaurs and the Origin of Flight: The Dinosaur Museum Journal 1. Blanding: The Dinosaur Museum. pp. 16–26.
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- ^ Czerkas, S.A., and Yuan, C. (2002). "An arboreal maniraptoran from northeast China." Pp. 63-95 in Czerkas, S.J. (Ed.), Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum Journal 1. The Dinosaur Museum, Blanding, U.S.A. PDF abridged version
- ^ Zhang, F., Zhou, Z., Xu, X. & Wang, X. (2002). "A juvenile coelurosaurian theropod from China indicates arboreal habits." Naturwissenschaften, 89(9): 394-398. doi=10.1007 /s00114-002-0353-8.
- ^ a b Mayr, G., Peters, D.S., Plodowski, G. and Vogel, O. (2002). "Bristle-like integumentary structures at the tail of the horned dinosaur Psittacosaurus." Naturwissenschaften, 89: 361–365. Cite error: The named reference "mayretal2002" was defined multiple times with different content (see the help page).
- ^ Xu, X. and Wang, X.-L. (2003). "A new maniraptoran from the Early Cretaceous Yixian Formation of western Liaoning." Vertebrata PalAsiatica, 41(3): 195–202.
- ^ a b Xu, X., Norell, M. A., Kuang, X., Wang, X., Zhao, Q., Jia, C. (2004). "Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids". Nature. 431 (7009): 680–684. doi:10.1038/nature02855. PMID 15470426.
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- ^ Xu, X., and Zhang, F. (2005). "A new maniraptoran dinosaur from China with long feathers on the metatarsus." Naturwissenschaften, 92(4): 173 - 177.
- ^ Ji, Q., Ji, S., Lu, J., You, H., Chen, W., Liu, Y., and Liu, Y. (2005). "First avialan bird from China (Jinfengopteryx elegans gen. et sp. nov.)." Geological Bulletin of China, 24(3): 197-205.
- ^ Turner, Alan H. (2007). "A basal dromaeosaurid and size evolution preceding avian flight" (pdf). Science. 317 (5843): 1378–1381. doi:10.1126/science.1144066. PMID 17823350.
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suggested) (help) - ^ Goehlich, U.B., Tischlinger, H., and Chiappe, L.M. (2006). "Juraventaor starki (Reptilia, Theropoda) ein nuer Raubdinosaurier aus dem Oberjura der Suedlichen Frankenalb (Sueddeutschland): Skelettanatomie und Wiechteilbefunde." Archaeopteryx, 24: 1-26.
- ^ Ji, S., Ji, Q., Lu J., and Yuan, C. (2007). "A new giant compsognathid dinosaur with long filamentous integuments from Lower Cretaceous of Northeastern China." Acta Geologica Sinica, 81(1): 8-15.
- ^ He, T., Wang, X.-L., and Zhou, Z.-H. (2008). "A new genus and species of caudipterid dinosaur from the Lower Cretaceous Jiufotang Formation of western Liaoning, China." Vertebrata PalAsiatica, 46(3): 178-189.
- ^ Xu, X., Zheng, X. and You, H. (2010). "Exceptional dinosaur fossils show ontogenetic development of early feathers." Nature, 464: 1338-1341. {{doi:10.1038/nature08965}}
- ^ Zhang, F., Zhou, Z., Xu, X., Wang, X., & Sullivan, C. (2008). "A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers." Available from Nature Precedings, doi:10.1038/npre.2008.2326.1 [2].
- ^ Xu, X., Zhao, Q., Norell, M., Sullivan, C., Hone, D., Erickson, G., Wang, X., Han, F. and Guo, Y. (in press). "A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin." Chinese Science Bulletin, 6 pages, accepted November 15, 2008.
- ^ a b c Zheng, X.-T., You, H.-L., Xu, X. and Dong, Z.-M. (2009). "An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures." Nature, 458(19): 333-336. doi:10.1038/nature07856
- ^ Ortega F., Escaso, F. and Sanz, J.L. (2010). "A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain." Nature, 467: 203-206.
- ^ Czerkas, S.A., and Ji, Q. (2002). "A new rhamphorhynchoid with a headcrest and complex integumentary structures." Pp. 15-41 in: Czerkas, S.J. (Ed.). Feathered Dinosaurs and the Origin of Flight. Blanding, Utah: The Dinosaur Museum. ISBN 1-932075-01-1.
- ^ a b Prum, R. & Brush A.H. (2002). "The evolutionary origin and diversification of feathers". The Quarterly Review of Biology. 77 (3): 261–295. doi:10.1086/341993. PMID 12365352.
- ^ Norell, M. Xu, X. (2005) "The Varieties of Tyrannosaurs" Natural History Magazine May, 2005. http://www.naturalhistorymag.com/htmlsite/master.html?http://www.naturalhistorymag.com/htmlsite/0505/0505_feature.html
- ^ Xu, X. Zheng, X. You, H. "A New Feather Type in a Nonavian Theropod and the Evolution of Feathers" Proceedings of the National Academy of Science. January 20, 2009
- ^ 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
- ^ Göhlich, U.B., and Chiappe, L.M. (2006). "A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago." Nature, 440: 329-332.
External links
- DinoBuzz, dinosaur-bird controversy explained, by UC Berkeley.
- Journal of Dinosaur Paleontology, with many articles on dinosaur-bird links.
- Life-like images of feathered dinosaurs