264 



Ageneiosus n. sp. 



Figs. 21, 27, 29, 47-48 



Tables 17-18 



Ageneiosus vittatus: Burgess 1989:629 (photograph [misidentified]; specimen 

 from Rio Tefe). - . ^ .- • 



Diagnosis 



- : , V Ageneiosus n. sp. is distinguished from all other members of the genus by its 

 unique coloration pattern, predominated by a very discrete brown midlateral stripe 

 that is subtended above and below by unpigmented stripes of nearly equal width. A 

 combination of the forked tail, encapsulated swimbladder, and moderate size 

 separates this species from all others except yl. ucayalemis,A. valenciennesi,A. 

 pardalis, and^. vittatus. Distinguished from the last three species, however, by a 

 combination of the slightly shorter anal fin, modally fewer ribs and vertebrae, and 

 the absence of mottling or spotting. Confusion between y4. n. sp. and either y4. 

 valenciennesi ox A. pardalis is not likely because of the distantly allopatric 

 distributions of these three species, as well as the pronounced differences in size, 

 coloration, and other morphological characteristics. Ageneiosus n. sp. differs from 

 A. vittatus in having fewer pairs of ribs (modally 7 versus 9); a slightly shorter 

 vertebral column (44-47 [X = 45.4] versus 45-48 [x = 46.5] total vertebrae, and 16- 

 18 [X = 17.2] versus 17-20 [X = 18.4] preanal vertebrae); slightly more branched 

 pectoral fin rays (modally 13 versus 12); a much more flattened head and 

 compressed body; and a considerably different pigmentation pattern. Ageneiosus n. 

 sp. is most similar to A. ucayalensis in body shape, both species having an extremely 

 flattened head, but distinguished from that species by a shorter anal fin (31-38 rays 

 versus 41-50 in ucayalensis), fewer gill rakers (11-18 versus 18-25), fewer total 

 vertebrae (44-47 versus 46-55), and a markedly different pigmentation pattern. 



