eighth lepidotrichia. In prereproductive males, the lepidotrichia become thicker 

 and elongated, and are closely apposed (Fig. 29). There is negligible to slight 

 thickening of the corresponding pterygiophores, but the normally cartilaginous distal 

 radials become large, ossified nodules. The urogenital pore migrates from its usual 

 position at the base of the fin to the distal tip of the coalesced rays, the entire 

 structure therefore being transformed into an intromittent organ, or gonopodium. 

 Among ageneiosid species there is little variation in osteology of the gonopodium. 

 Development of the gonopodium is subject to seasonality, as discussed below in 

 greater detail. 



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Caudal Skeleton -. : - v- 



Early descriptions of ageneiosids generally mentioned few details about the 

 caudal fin; comments about the tail were usually limited to descriptions of the 

 general shape or coloration of the fin. Some authors gave ray counts, presumably of 

 branched lepidotrichia. From these accounts, no generalizations could be made 

 about osteology of the ageneiosid caudal skeleton. 



Lundberg and Baskin (1969) examined caudal skeleton morphology in a 

 variety of catfishes, but included .4. /jorfifa/iy (AMNH 11395) as their only 

 representative ageneiosid. While providing valuable data for interfamilial 

 comparisons, Lundberg and Baskin's (1969) study failed to adequately characterize 

 the hypural morphology of ageneiosids. Three major features of the siluroid caudal 

 skeleton were examined by these authors; the degree of fusion of the hypural 

 elements, evolutionary development of the hypurapophysis, and the number of 

 principal rays. Data on the first two characters were presented that compared a 

 large number of taxa, and the authors provided evidence of possible relationships 

 and general phyletic trends based on these characters. With regard to the number 

 of rays, Lundberg and Baskin (1969) admitted that many studies, including theirs. 



