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Sarcopterygii
The Sarcopterygii or lobe-finned fish (from Greek σαρξ ''sarx'', flesh, and πτερυξ ''pteryx'', fin) – sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek κροσσός ''krossos'', fringe) – constitute a clade (traditionally a class or subclass) of the bony fish, though a strict cladistic view includes the terrestrial vertebrates. The living sarcopterygians are the coelacanths, lungfish, and the tetrapods.
==Characteristics==
Early lobe-finned fishes are bony fish with fleshy, lobed, paired fins, which are joined to the body by a single bone.〔Clack, J. A. (2002) ''Gaining Ground''. Indiana University〕 The fins of lobe-finned fishes differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. The scales of sarcopterygians are true scaloids, consisting of lamellar bone surrounded by layers of vascular bone, dentine-like cosmine, and external keratin.〔Kardong, Kenneth V. (1998). Vertebrates: Comparative Anatomy, Function, Evolution, second edition, USA: McGraw-Hill, 747 pp.. ISBN 0-07-115356-X/0-697-28654-1.〕 Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of actinopterygians (ray-finned fish). The braincase of sarcopterygians primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early sarcopterygians have a symmetrical tail. All sarcopterygians possess teeth covered with true enamel.
Most species of lobe-finned fishes are extinct. The largest known lobe-finned fish was ''Rhizodus hibberti'' from the Carboniferous period of Scotland which may have exceeded 7 meters in length. Among the two groups of extant (living) species, the coelacanths and the lungfishes, the largest species is the West Indian Ocean coelacanth, reaching 2 m (6.5 ft) in length and weighing up 110 kg (240 lb). The largest lungfish is the African lungfish which can reach 2 m (6.6 ft) in length and weigh up to 50 kg (110 lb).〔(Protopterus aethiopicus ). Fishing-worldrecords.com〕
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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