On the osteology and myology of the cephalic region and pectoral girdle of Nematogenys inermis (Ghichenot, 1848), with comments on the autapomorphies and phylo- genetic relationships of the Nematogenyidae (Teleostei : Siluriformes)

The cephalic and pectoral girdle structures of Nematogenys inermis are described and compared to those of other catfishes, as the foundation for a discussion on the autapomorphies and phylogenetic relationships of the Nematogenyidae. Our observations and comparisons indicate that nematogenyids are defined, at least, by two unique, autapomorphic characters, namely : 1) anterior margin of prevomer markedly extended anteriorly, at about the same level of anterior margin of mesethmoid; 2) anterior ceratohyal with prominent, posteriorly pointed, posterodorsal projection bordering a significant part of the dorsal margin of the posterior ceratohyal. With respect to the phylogenetic relationships of the Nematogenyidae, this study supports Mo's 1991 and de Pinna's 1992 phylogenetic hypotheses according to which the nematogenyids and the trichomycterids are sister-groups.