ABSTRACT
Taxonomic group created by Linnaeus in his Systema naturae, in which he included the bony fishes having the pelvic fins in an abdominal position. This feature represents, in the evolution of fishes, the most primitive stage of the position of the pelvic fins. Taxonomic group created by Linnaeus to assemble the bony fishes which have the pelvic fins in front of the pectoral fins, as in the cod family. An interesting case of the difficulty is the double specific name given to the Atlantic cod by Linnaeus in his Systema natures, in his belief that they were two different species. The abdominal fishes include, among others, salmon, trout, and herring. The absence of pelvic fins represents the most recent stage in the evolutionary migration of the pelvic fins towards the head, from a primitive position in the abdominal region, to their complete disappearance, as in the eel and moray.
