Sarcopterygian
| Lobe-finned fishes Temporal range: Late Silurian - Present, 419–0 Ma |
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| Coelacanth | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Superclass: | Osteichthyes |
| Class: |
Sarcopterygii Romer, 1955 |
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The Sarcopterygii /ˌsɑːrkɒptəˈrɪdʒi.aɪ/ 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 and lungfish; additionally, all tetrapods are sarcopterygians or descendants of them (including humans).
Early lobe-finned fishes are bony fish with fleshy, lobed, paired fins, which are joined to the body by a single bone. 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. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into the 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.
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