ribs 5-6. Gill rakers relatively long and numerous, totalling 21-32 on outside row 

 of first gill arch Ageneiosus brevis. 



lib. Prominent large black patches of pigment on top of the snout, the lips, the 

 chin, on the sides above the anal fin, and with a stripe in each lobe of the caudal 

 fin. Top of head relatively flat and smoothly angled upward to dorsal fin origin. 

 Postcleithral process never present. Anal fin short, with 23-30 rays. Preanal 

 vertebrae 17-19. Paired ribs 7-8. Total gill rakers on outside row of first arch 

 14-23 Ageneiosus atronasus. 



Family Ageneiosidae 



Diagnosis - 



Distributed in the neotropics south of the isthmus of Panama. Members of 

 the Ageneiosidae have internal fertilization and exhibit unique sexual dimorphism 

 of the maxillary barbels, dorsal fin spine, and anal fin, a condition that is shared 

 among other siluriforms only with at least some taxa currently classified in the 

 family Auchenipteridae {sensu lato). Further distinguished from all other catfishes 

 by the following unique combination of characters: body strongly compressed and 

 head greatly flattened, with ventrolaterally positioned eyes; maxillary barbels short 

 in females and immature males, concealed within rictal grooves above upper lip; 

 maxilla of nuptial males extending into maxillary barbel as an osseous core, with 

 sharp, recurved hooks on dorsal margin in all species except Tetranematichthys 

 quadrifilis; chin barbels absent or reduced to a single pair in adults; dermal ■ 



component of basal radial of first dorsal fin element not expanded into a broad 

 plate on posterodorsal aspect of neurocranium; anterior margin of basal radial of 

 second dorsal fin element sutured to posteroventral margin of supraoccipital; 



