On the osteology and myology of the cephalic region and pectoral girdle of Chaca bankanensis Bleeker 1852, with comments on the autapomorphies and phylogenetic relationships of the Chacidae (Teleostei: Siluriformes)

The cephalic and pectoral girdle structures of Chaca bankanensis are described and compared to those of other catfishes, as the foundation for a discussion on the autapomorphies and phylogenetic relationships of the Chacidae. Our observations and comparisons pointed out six new chacid autapomorphies, namely: (1) absence of abductor superficialis; (2) ethmoid cartilage with long, thin, anterolateral projections situated ventrally to the anterolateral arms of mesethmoid; (3) interopercular with well-developed, deep concavity to articulate with posterior surface of preopercular; (4) dorsal process 2 of the cleithrum highly developed and markedly extended posteriorly. In addition, our observations and comparisons support a close relationship between the chacids, the plotosids and the clariids.