■*..>♦,. 



ageneiosids is probably correlated with their feeding habits; most species for which 

 there are data feed predominately on whole fishes and decapods. 



The siluroid palatine is fairly variable in structure and orientation, relating to 

 the mechanism of adduction of the maxillary barbel, and is of considerable 

 systematic value (Gosline 1975). In ageneiosids, the palatine typically is a rod- 

 shaped bone with cartilaginous plates at each end, articulating in a sliding 

 mechanism with the maxillary anteriorly and the lateral ethmoid medially. This 

 condition occurs in females and immature males, and is similar to that found in a 

 number of other catfishes (Alexander 1965, Gosline 1975). In nuptial male 

 ageneiosids, however, the palatine is considerably modified, with an enlarged 

 anterior facet and a slightly expanded medial cartilage. This modification of the 

 palatine is also present in nuptial males of certain auchenipterids, including .^ 

 Auchenipterus, Entomocorus, Epapterus, and at least some species of Trachefyopterus. 

 Ferraris (1988) regarded the modified palatine as a synapomorphy of a restricted 

 clade within his subfamily Auchenipterinae; the absence of a modified palatine in 

 Trachefyichthys and some species of Trachefyopterus were thought by Ferraris (1988) 

 to be secondary losses from the presumably derived modification. Functionally, the 

 expansion of the palatine is apparently correlated with the sexually dimorphic 

 hyperossification of the maxillary barbel in nuptial males. In taxa with this 

 apomorphy, the barbels of breeding males are abducted in a lateral to anterodorsal 

 plane and have a tactile function during courtship and spawning. A hypothesized 

 close relationship between the taxa sharing this character state is corroborated by 

 additional characters associated with sexual dimorphism (Ferraris 1988). However, 

 I tentatively question the distribution of this character state as proposed by Ferraris 

 (1988), inasmuch as published data are unavailable for breeding males of most 

 species, including some members of his non-monophyletic "group 1" species of 



