In the last decade catfish morphology has yielded some features which call for a reappraisal of their character-states, particularly from an evolutionary point of view. These features have been either wholly unseen or seen but little understood. Indeed, catfish may be endowed with many more structures yet to be understood. Catfishes are singular among extant fishes in lacking a pseudobranch and in possessing a cavernous carotid labyrinth, the morphology of which is comparable to that of amphibians. There is great controversy over the homology of this unique character of catfishes. Apart from the catfish group, a few more teleosts possess electroreceptors. This chapter summarizes the thinking on the phylogenetic relationships of the extant bony fishes. The phylogenetic and systematic status of the catfish group is subject to revision, yet evidence suggests that they represent a more primitive status than hitherto held. Future researchers of the twenty-first century will illuminate this and similar issues unresolved in fish morphology.