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ACTINOPTERYGII

Ray-finned Fishes

The Actinopterygii includes approximately 33,000 valid species (Eschmeyer and Fong, 2013) classified by Nelson (2006) in 453 families. They are found in all aquatic habitats occupied by vertebrates and range vastly in body size from a tiny species of the gobiiform genus Schindleria that grows no longer than 1 cm (and ca 0.7 mg) and spends its entire short life in the plankton, to the Oarfish (Regalecus) that grows to over 8 m in length, to the Ocean Sunfish (Mola mola) that weighs up to 2,300 kg. Given this enormous diversity, it is not surprising that the group is difficult to characterize morphologically. Extant actinopterygians have enlarged basal elements in the pectoral fins and fused basal elements in the pelvic fins (Lauder and Liem, 1983; Patterson, 1982). Early lineages (i.e., non-teleosts) have a single dorsal fin (variously lost or divided in many) and ganoid scales (variously lost or modified in most species). Several studies (e.g., Faircloth et al., 2013; Hurley et al., 2007; Inoue et al., 2003; Lauder and Liem, 1983) have examined the relationships among the major lineages of the Actinopterygii.

Hypothesized phylogenetic relationships of the early lineages of actinopterygians (after Faircloth et al., 2013).