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''Voalavo gymnocaudus'', also known as the northern voalavo, naked-tailed voalavo, or just voalavo, is a rodent in the family Nesomyidae found in the highlands of northern Madagascar. Discovered in 1994 and formally described in 1998, it is the type species of genus ''Voalavo''; its closest relative is ''Voalavo antsahabensis'' of the Central Highlands. DNA sequence data suggests it may be more closely related to ''Eliurus grandidieri'' than to other species of the closely related genus ''Eliurus''. ''V. gymnocaudus'' is found at above sea level in montane wet and dry forest in the Marojejy and Anjanaharibe-Sud massifs. Nocturnal and solitary, it lives mainly on the ground, but can climb, and probably eats plant matter. Despite a small range, it is classified as "Least Concern" because it lacks obvious threats and much of its range is within protected areas. ''Voalavo gymnocaudus'' is a small, mouse-like rodent with soft, gray fur which is only slightly darker above than below. The ears are short and rounded. The long tail appears mostly naked and lacks a distinct tuft, which is present in ''Eliurus''. It differs from ''V. antsahabensis'' mainly in the values of some measurements. The skull is delicate, with a long, narrow rostrum (front part), narrow interorbital region (between the eyes), and no development of ridges on the braincase. The molars are relatively high-crowned (hypsodont). Body mass is . ==Taxonomy== The rodent fauna of the Northern Highlands of Madagascar remained almost totally unstudied until the 1990s. A 1994 survey of the Anjanaharibe-Sud Reserve partially filled this gap and led to the discovery of two new species: ''Eliurus grandidieri'' (genus ''Eliurus'') and ''Voalavo gymnocaudus'', the first known and type species of the genus ''Voalavo''. Both species were formally described in 1998 by Michael Carleton and Steven Goodman. The generic name, ''Voalavo'', is a general Malagasy word for rodent, and the specific name, ''gymnocaudus'', refers to the naked tail, which distinguishes ''V. gymnocaudus'' from the related tufted-tailed rats (''Eliurus''). In 2000, the species was also recorded from the nearby Marojejy National Park. Meanwhile, in 1999, Sharon Jansa and colleagues published a molecular phylogenetic study of the Nesomyinae, the native Malagasy rodents, using the mitochondrial gene cytochrome ''b''. Their results suggested that the current definitions of ''Eliurus'' and ''Voalavo'' may not be correct, because they found that ''V. gymnocaudus'' and ''E. grandidieri'' are more closely related to each other than to the remaining species of ''Eliurus''. However, the DNA of ''Eliurus petteri'', a possible close relative of ''E. grandidieri'', could not be sampled, so Jansa and colleagues recommended further evaluation of the problem. According to a 2003 report, data from nuclear genes also support the relationship between ''V. gymnocaudus'' and ''E. grandidieri'', but ''E. petteri'' remains genetically unstudied and the taxonomic issue has not been resolved. A second species of ''Voalavo'', ''Voalavo antsahabensis'', was named in 2005 from central Madagascar. Morphological differences between the two are subtle but consistent, and the cytochrome ''b'' sequences of the two species differ by about 10%. In mammals, closely related species regularly differ by less than 5% in their cytochrome ''b'' sequences, and a divergence of more than 5% within a single species suggests the presence of cryptic species. 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「Voalavo gymnocaudus」の詳細全文を読む スポンサード リンク
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