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analysis of the morphological and functional aspects of the characters themselves, 

 and concludes with comments on the systematic significance of dimorphic 

 characters. A proportionally large amount of attention to the reproductive biology 

 is given here, resulting from a combination of the systematic implications and the 

 inherently interesting aspect of this feature of ageneiosids and auchenipterids. 

 Kner (1858a) dealt briefly with the taxonomic problems associated with 

 sexual dimorphism in his account of .4. brevifilis, and he illustrated or described 

 aspects of the reproductive system in^l. valenciennesi and a variety of other 

 neotropical catfishes. However, Kner's discussion of the reproductive anatomy in 

 Ageneiosus is highly problematic. In his account of yl. brevifilis, he cited comments 

 by Valenciennes (Cuvier and Valenciennes 1840:239) and unpublished notes of 

 Natterer, which suggested that^. inermis Lacepdde andy4. brevifilis Valenciennes 

 possibly represented females of^. militaris Bloch. Kner dispensed with this idea, by 

 arguing that the opinions of Valenciennes and Natterer about sexual dimorphism 

 were based on conjecture of local fishermen; he refuted the notion of possible 

 sexual dimorphism by stating that his specimens did not differ externally, despite the 

 fact that he had specimens of both sexes. It is not likely that Kner (1858a) 

 misidentified the sexes, inasmuch as he illustrated and discussed gross dimorphism 

 of the gonads in a number of catfish species, including a brief description at the end 

 of his account of y4. brevifilis. Based on his conclusions and description of the 

 gonads, it seems Ukely that Kner (1858a) had only nonreproductive individuals 

 available to him, and thus he erroneously assumed that sexual dimorphism does not 

 occur mA. brevifilis. The fact that Kner failed to appreciate seasonality of 

 reproductive dimorphism is further evident from his account of ^4. militaris 

 Valenciennes {= A. valenciennesi Bleeker, although he wrongly synonymized this 

 species with Silurus militaris Bloch). In that account, Kner described in detail the 

 external nuptial structures in males, but he equated the sexual dimorphism of males 

 with a taxonomic difference. The most enigmatic part of Kner's (1858a) treatment 



