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Praeornis
''Praeornis'' is a dubious genus of possible early bird, named on the basis of a single possible feather discovered in the Balabansai Formation of Kazakhstan by Sharov in 1971. A second specimen has recently been discovered by Dzik et al.〔
In 1978, Rautian officially named the feather (cataloged as specimen PIN 2585/32) ''Praeornis sharovi''. He believed it belonged to a bird more primitive than ''Archaeopteryx'', and assigned it to its own sublcass (Praeornithes), order (Praeornithiformes) and family (Praeornithidae).〔Rautian (1978). "A unique bird feather from Jurassic lake deposits in the Karatau." ''Paleontological Journal'', 4: 520-528.〕 However, in 1986, Bock published a paper arguing that the "feather" was in fact the leaf of a cycad.〔Bock (1986). "The arboreal origin of avian flight." Pp. 57-72 in Padian, K. (ed.). ''The Origin of Birds and the Evolution of Flight''. California Academy of Sciences, Memoir 8.〕 This opinion was followed by Doludenko and colleagues in 1990, who noted that it was similar to the leaves of the cycad species ''Paracycas harrisii''. L.A. Nessov, in 1992, also suggested that it belonged to a cycad, but synonymized it with the species ''Cycadites saportae''. The opinion that it represents a leaf has since been followed by Alan Feduccia in 1996 and Peter Wellnhofer in 2004.〔Feduccia, A. (1996). ''The Origin and Evolution of Birds''. New Haven: Yale University Press. 420 pp.〕〔Wellnhofer, P. (2004). "The plumage of ''Archaeopteryx'': Feathers of a dinosaur." Pp. 282-300 in Currie, Koppelhus, Shugar and Wright (eds). ''Feathered Dragons: Studies on the Transition from Dinosaurs to Birds''.〕
Three studies since the original description has supported the identification of ''Praeornis'' as a feather, rather than a leaf. In 1991, Glazunova and colleagues examined the specimen using an electron microscope, and found that the microstructure had features in common with the "primitive" feathers of ratite birds (ratites are now known to be secondarily flightless paleognathous birds, their feathers are not primitive but degenerate flight and contour feathers ).〔Glazunova, Rautian and Filin (1991). "''Praeornis sharovi'': Bird feather or plant leaf?" ''Materialy 10 Vsesoyuznoi Ornitologicheskoi Konferentzii, Vitebsk,'' 2(1): 149-150. (Russian )〕 In a 2001 paper, Kurochkin also accepted its identity as a feather.〔Kurochkin (2001). "Mesozoic birds of Mongolia and the former USSR." Pp. 533-559 in Benton, Shishkin, Unwin and Kurochkin (eds.). ''The Age of Dinosaurs in Russia and Mongolia.''〕 A more comprehensive study was published in 2010 by Dzik et al., in which the authors conducted a biochemical analysis of a ''Praeornis'' feather and other fossils from the same site, including plants and fish. The analysis showed that the chemical markers of the ''Praeornis'' fossil was more similar to the fish scales than to the plant leaves, supporting the hypothesis that the feathers were animal in origin.〔Dzik, J., Sulej, T. and Niedzwiedzki, G. (2010). "Possible link connecting reptilian scales with avian feathers from the early Late Jurassic of Kazakstan." ''Historical Biology'', 22(4): 394–402. ()〕 Besides identifying ''Praeornis'' as a feather, Dzik et al. also noticed similarities between the purported feathers of ''Longisquama'' and those of ''Praeornis''.〔
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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