Osteology and myology of the cephalic region and pectoral girdle of the South African catfish Austroglanis gilli, with comments on the autapomorphies and phylogenetic relationships of the Austroglanididae (Teleostei: Siluriformes)

The cephalic and pectoral girdle structures of the South African catfish Austroglanis gilli are described and compared with those of other catfishes, either studied by us or described in the literature, as the foundation for a discussion on Austroglanididae autapomorphies, and also on the phylogenetic relationships between the austroglanidids and the other catfishes. Our observations, comparisons, and bibliographical overview revealed only two Austroglanidae autapomorphies, namely: 1) the peculiarly shaped, posteriorly bifurcated sesamoid bone 1 of the suspensorium; and 2) the markedly broad fourth basibranchial. Another feature, the marked lateral bifurcation of the anterodorsolateral laminar projection of the sphenotic bone, may eventually constitute an additional austroglanidid autapomorphy, but, perhaps more reasonably, be a synapomorphic feature to support a close relationship between A. gilli and A. barnardi. With respect to the phylogenetic position of the Austroglanididae within the Siluriformes, these fishes seem to be closely related to the ictalurid and the cranoglanidid, and particularly to the ariid and the claroteid catfishes.