ABSTRACT
The Siluriformes have long been included in the Ostariophysi. This superorder contains slightly more than 25% of the teleost species and about 80% of all freshwater fishes, including, apart from the Siluriformes, the Gonorynchiformes, Cypriniformes, Characiformes and Gymnotiformes (Fig. 1.2) (Nelson, 1994; Teugels, 1996) [Note: as a precautionary measure, the extraordinary and rem arkable tentative new ostariophysan order Sorbininardiformes of Taveme (1999) has not been included here because more data and a greater general consensus concerning its status are needed.] The ostariophysans are recognised, as their name indicates (osteon= bone;
fysis= bladder), by a specialised set of anterior vertebrae associated with the swim bladder. This specialisation is significantly less developed in members of the series Anatophysi (Gonorynchiformes), however, than in members of the other ostariophysan series, the Otophysi (Cypriniformes, Characiformes, Gymnotiformes and Siluriformes), where a true chain of Weberian ossicles interconnects the swim bladder and the labyrinth organ (see, Fink and Fink, 1981,1996; Gayet and Chardon, 1987; Poyato-Ariza, 1996; Grande and PoyatoAriza, 1999).
