On the anatomy and function of the cephalic structures in Phractura (Siluriformes: Amphiliidae), with comments on some striking homoplasies occurring between the Doumeinae and some Loricaroid catfishes

The morphology and function of the cephalic structures related to the feeding mechanism - movements of the mouth, suspensorium, opercular series, hyoid arch, maxillary barbels and mandibular bar- bels - was studied in two catfish species of the genus Phractura (Amphiliidae: Doumeinae), P. intermedia and P. brevicauda. For comparison, other species of the family Amphiliidae, as well as a large number of other cat- fishes, were also studied. The morpho-functional analysis pointed out that Phractura, as well as the other doumeins, present several unusual morphological modifications, which are very likely related to two main functional specialisations: the ability to attach the body to the substrate with an oral sucker, and the ability to scrape this substrate. The comparison with other siluriforms revealed an impressive number of morpho-func- tional homoplasies occurring between the African doumeins and the South-American callichthyids, scolo- placids, astroblepids and loricariids.