K ,: ^.- / . - ''■ ■- ■ ■ 76 



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that the barbels of Siluriformes and Cypriniformes were independently derived, and, 

 citing the lability of barbel development and placement among members of their 

 subseries Cypriniphysi, probably had evolved several times within the 

 Cypriniformes. Excluding the maxillary pair, there is considerable variation among 

 catfishes in the structure, topography, and taxonomic distribution of the remaining 

 barbels, which may suggest that they too were derived independently in certain 

 lineages. Moreover, there is considerable variation in the ontogenetic development 

 of barbels, leading Fuiman (1984:137) to suggest that "heterochrony in barbels may 

 be an important consideration for classification within siluroids." Nevertheless, 

 given the universal distribution and unique, complex morphology of the siluroid 

 maxillary barbel and associated structures (Gosline 1975), there is no compelling 

 evidence to refute a hypothesis that this organ is homologous among all extant 

 siluroid taxa, and perhaps represents a synapomorphy of equal weight as the degree 

 of fusion of the Weberian complex in defining the monophyly of siluroids. 



The enigmatic nature of the barbels in the Ageneiosidae is reflected in the 

 family name, from the Greek ageneios, meaning beardless. Excluding 

 Tetranematichthys, most previous diagnoses of the family emphasized reduction of 

 the maxillary barbels and the absence of any on the chin. Toothed maxillary barbels 

 were occasionally mentioned in original descriptions, but, with very few exceptions 

 (e.g., Kner 1858a, Eigenmann and Bean 1907), sexual dimorphism of the barbels 

 was apparently not known or understood by most authors. Thus, in all prior 

 classifications, the absence of barbels except for the maxillary pair has been used to 

 separate ageneiosids from other families of catfishes (notwithstanding confusion 

 surrounding the placement of Tetranematichthys, reviewed separately in a section on 

 its taxonomic status). No studies have suggested that chin barbels are present, 

 during any stage of development, in individuals of any species of Ageneiosus. 



