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The genus ''Pauxi'' consists of the three species of helmeted curassows, terrestrial black fowl with ornamental casque on their heads. All are found in South America. This genus contains 3 species * Helmeted curassow or northern helmeted curassow, ''Pauxi pauxi'' * Horned curassow, ''Pauxi unicornis'' * Sira curassow, ''Pauxi koepckeae'' As indicated by analysis of mt and nDNA sequences and calibrated with geological data, this genus' ancestors probably diverged from those of ''Mitu'', their closest living relatives, in the Tortonian (early Late Miocene), some 8-7.4 mya. How the present distribution in 4 small areas quite distant from each other came to be is not known. Given that helmeted curassows are birds of the foothills and uplands, it might be that the ancestral ''Pauxi'' population became fragmented by the uplift of the Andes, which in their area of distribution took place during the Late Miocene, around the ''Pauxi''-''Mitu'' divergence and some time after.(Pereira & Baker 2002, Pereira ''et al.'' 2002). Pereira & Baker (2002) reported an interesting find: in the mtDNA phylogeny, ''Pauxi'' was paraphyletic, with ''P. unicornis'' being resolved as the sister species of ''Mitu tuberosa''. This, of course, does not automatically imply that they are closely related or that the genera are invalid. Rather, the authors point out, given the distinct and peculiar morphology of the two genera, incomplete lineage sorting or hybridization between ancestral individuals of the two species is a more likely explanation. According to their data, there must have been some extent of gene flow between ''Mitu tuberosa'' and ''P. unicornis'' around 2 mya. Unfortunately, the authors do not provide subspecific identification of their single ''P. unicornis'' specimen. In any case, they took care to exclude captive hybridization in their choice of samples, as it is frequently known to occur in curassows and would have confounded the analysis. Altogether, what can be said with certainty is that there seems to have been some extent of hybridization between at least one population of the southern helmeted curassow and female razor-billed curassows at the end of the Pliocene. ==References== *Pereira, Sérgio Luiz & Baker, Allan J. (2004): Vicariant speciation of curassows (Aves, Cracidae): a hypothesis based on mitochondrial DNA phylogeny. ''Auk'' 121(3): 682-694. (with Spanish abstract ) DOI:10.1642/0004-8038(2004)121()2.0.CO;2 (HTML abstract ) (HTML fulltext without images ) *Pereira, Sérgio Luiz; Baker, Allan J.& Wajntal, Anita (2002): Combined nuclear and mitochondrial DNA sequences resolve generic relationships within the Cracidae (Galliformes, Aves). ''Systematic Biology'' 51(6): 946-958. PMID 12554460 (PDF fulltext ) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pauxi」の詳細全文を読む スポンサード リンク
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