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The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae (hares and rabbits) and the Ochotonidae (pikas). The name of the order is derived from the Ancient Greek ''lagos'' (λαγώς, "hare") +''morphē'' (μορφή, "form"). There are about eighty-seven species of lagomorph, including about twenty-nine species of pika, twenty-eight species of rabbit and cottontail, and thirty species of hare. == Taxonomy and evolutionary history == Other names used for this order, now considered synonymous, include: ''Duplicidentata'' - Illiger, 1811; ''Leporida'' - Averianov, 1999; ''Neolagomorpha'' - Averianov, 1999; ''Ochotonida'' - Averianov, 1999; and ''Palarodentia'' - Haeckel, 1895.〔 The extinct family Prolagidae is represented by a single species, the Sardinian pika ''Prolagus sardus'', fossils of which are known from Sardinia, Corsica, and nearby small islands. It may have survived until about 1774. The evolutionary history of the lagomorphs is still not well understood. Until recently, it was generally agreed that ''Eurymylus'', which lived in eastern Asia and dates back to the late Paleocene or early Eocene, was an ancestor of the lagomorphs. More recent examination of the fossil evidence suggests that the lagomorphs may have instead descended from Anagaloidea, also known as "mimotonids", while ''Eurymylus'' was more closely related to rodents (although not a direct ancestor). The leporids first appeared in the late Eocene and rapidly spread throughout the Northern Hemisphere; they show a trend towards increasingly long hind limbs as the modern leaping gait developed. The pikas appeared somewhat later in the Oligocene of eastern Asia. Lagomorphs were certainly more diverse in the past than in the present, with around 75 genera and over 230 species represented in the fossil record and many more species in a single biome. This is evidence that lagomorph lineages are declining. Recent finds suggest an Indian origin for the clade, having possibly evolved in isolation when India was an island continent in the Paleocene.〔Rose K.D., Deleon V.B., Mmissian P., Rana R.S., Sahni A., Singh L. & Smith T. (2008). – Early Eocene lagomorph (Mammalia) from western India and the early diversification of Lagomorpha. – Proc. Royal Society B, RSPB 2007.1661.R1〕 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「Lagomorpha」の詳細全文を読む スポンサード リンク
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