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The Telencephalon of Sarcopterygian Fishes

1990; Springer Nature; Linguagem: Inglês

10.1007/978-1-4757-9622-3_3

1566-6816

Rudolf Nieuwenhuys, J. Meek,

Marine animal studies overview

Crossopterygians are a distinctive and once widespread group of fishes, first known from rocks of Devonian age. They are characterized by the possession of two dorsal fins, the cosmoid structure of their scales and dermal bones, and well-formed fleshy-lobed paired fins. The internal skeleton of the latter is much concentrated so that only a single bone (humerus, femur) articulates proximally with the girdles and distally with two bones (radius and ulna, tibia and fibula). The latter are followed by the more variable distal fin supports. The most important distinguishing feature of these fishes is the division of the neurocranium into two parts, an anterior, ethmo-sphenoid portion and a posterior, otico-occipital portion with an intracranial joint between them. The large, persistent notochord inserts upon the postero-ventral margin of the ethmosphenoid portion of the skull (Thomson, 1969; Moy-Thomas and Miles, 1971; Andrews, 1973).