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Boidae (Common names: boas, boids, boioids) is a family of nonvenomous snakes found in America, Africa, Europe, Asia, and some Pacific Islands. Relatively primitive snakes, adults are medium to large in size, with females usually larger than the males. Two subfamilies, comprising eight genera and 43 species, are currently recognized.〔 ==Description== Like the pythons, boas have elongated supratemporal bones. The quadrate bones are also elongated, but not as much, while both are capable of moving freely so when they swing sideways to their maximum extent, the distance between the hinges of the lower jaw is greatly increased.〔Parker HW, Grandison AGC. 1977. Snakes -- a natural history. Second Edition. British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN 0-8014-1095-9 (cloth), ISBN 0-8014-9164-9 (paper).〕 Both families share a number of primitive characteristics. Nearly all have a relatively rigid lower jaw with a coronoid element, as well as a vestigial pelvic girdle with hind limbs that are partially visible as a pair of spurs, one on either side of the vent. In males, these anal spurs are larger and more conspicuous than in females. A long row of palatal teeth is present, and most species have a functional left lung that can be up to 75% as large as the right lung.〔〔(Boidae ) at (VMNH ). Accessed 15 July 2008.〕 Boids are, however, distinguished from the pythons in that none has postfrontal bones or premaxillary teeth, and that they give birth to live young. When labial pits are present, these are located between the scales as opposed to on them. Also, their geographical distributions are almost entirely mutually exclusive. In the few areas where they do coexist, the tendency is for them to occupy different habitats.〔 Formerly, boas were said to be found in the New World and pythons in the Old World, but with boid species present in Madagascar, Fiji, and the Solomon Islands, this is not quite accurate; instead, it seems they have survived in evolutionarily isolated areas. South America was isolated until a few million years ago, with a fauna that included marsupials and other distinctive mammals. With the formation of the Panamanian land bridge to North America about three million years ago, boids have migrated north as colubrids (and various Nearctic mammals) have migrated south, as part of the Great American Interchange. 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「boidae」の詳細全文を読む スポンサード リンク
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