node iox Ageneiosus. The six trees were input into Swofford's CONTREE program, 

 which constructs a strict consensus tree of all of the equally parsimonious trees. The 

 resulting tree topology is presented in Fig. 35. ' 



An analysis of the character-state distributions among the six equally 

 parsimonious trees indicates that most of the homoplasy involves meristic data. In 

 the following detailed analysis of characters themselves, parenthetical references 

 are to character numbers listed in Table 5 and the character suites or nodes 

 designated by letters on Fig. 35. 



Ferraris (1988) determined that the Ageneiosidae is monophyletic (Node A 

 on Fig. 35) on the basis of the following partial suite of characters: hyomandibula 

 separated from metapterygoid by a dorsomedial laminar ossification of the quadrate 

 (1); nasal bones bifurcated, with anterolateral canal ossified at base (2); vomer 

 broadly rounded, without anterolateral angular projections (3); nuchal plate formed 

 from dermal element of first dorsal-fin pterygiophore absent or fused to 

 posteroventral margin of supraoccipital (4); third basal radial of pectoral fin 

 expanded, supporting many fin rays (6); tips of first and second hypobranchials 

 concave and obliquely angled anteromedially (7); medial tip of first epibranchial 

 enlarged and dorsally covering medial tip of second epibranchial (8); urohyal with a 

 laminar ossification extending dorsomedially between anterior tips of hypohyals (9); 

 and, anterior ceratohyal sutured to ventral hypohyal along ventromedial surface 

 (10). I have little to add to Ferraris' (1988) list of synapomorphies of the 

 Ageneiosidae, but note the following. All ageneiosids lack a mandibular pair of 

 barbels, and, with the exception of Tetranematichthys, lose the mental barbels early 

 in their ontogeny. The presence of only a single pair of barbels on the chin is found 

 only in the auchenipterid genus Gelanoglemis, among all other neotropical catfishes, 

 and is considered to be convergent with the condition in ageneiosids (Ferraris 1988) 

 in the absence of corroborative evidence to unite these taxa. Ferraris (1988) 



