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Sarcopterygian fossil

Sarcopterygians are a group of prehistoric fish.

Facts

They are traditionally classed as lobe-finned fishes, which in the real world include the modern day lungfish and the coelacanth, Latimeria. These are bony fish with paired rounded fins. The fin-limbs of sarcopterygiians are so like the expected ancestral form of tetrapod limbs that they have been universally considered the direct ancestors of land vertebrates.

Sarcopterygians have modified cosmoid scales, which are thinner than true cosmoid scales, which can only be found on extinct fish. Coelacanths also have a special electroreceptive device called a rostral organ in the front of the skull, which probably helps in prey detection.

Characteristic

Sarcopterygians - crossopterygians are bony fish with fleshy-, lobed-paired fins, which are joined to the body by a single bone. 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 fishes). The braincase of sarcoptergygians primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early sarcopts have a symmetrical tail. Most taxonomists who subscribe to the cladistic approach include the grouping Tetrapoda within this group, which in turns consists of all species of four-limbed vertebrates. The fin-limbs of sarcopterygians show such a strong similarity to the expected ancestral form of tetrapod limbs that they have been universally considered the direct ancestors of tetrapods in the scientific literature