Morphological description of the cephalic region of Bagrus docmac, with a reflection on bagridae (teleostei: Siluriformes) autapomorphies

The cephalic structures of Bagrus docmac (Forsskal 1775) are described and compared with those of other bagrids and out-group siluroids as the foundation for a phylogenetic analysis of the Bagridae autapomorphies. From the six characters usually accepted in the literature as bagrid autapomorphies - prominent posterior process of the posttemporal; presence of a retractor posttemporalis muscle; large heavily ossified posttemporal; well-developed posttemporal fossa with a postero-lateral exit; thickened dorso-medial limb of the posttemporal; large, crescentic vomerine head - only the first five can be considered as such, since the shape of the vomer is quite similar to that in some other out-group catfishes. However, one other morphological feature is shown to be a bagrid autapomorphy: the differentiation of the adductor mandibulae A3'-d into a large and a small sub-division, inserted on the posterior and postero-dorsal edges of the coronomeckelian bone, respectively. Bagridae autapomorphies are very likely related to the production of sound and to the reinforcement of the efficiency of mouth closure, and may explain the biological success of bagrids among Ancient World catfishes, and, particularly, on the Asiatic continent.