y * 320 



medial margin present in most other species. Some specimens from dark waters 

 have superficial spots on the head and dorsum similar to A. pofystictus, but can be 

 readily separated on the basis of the obliquely truncate caudal fin, versus a 

 moderately forked to strongly emarginate fin with white or yellow tips of the lobes 

 in pofystictus. , 



Description 



A large species, commonly exceeding 30 cm SL and reaching a maximum size 

 of 47 cm SL in the material examined during this study; reportedly reaching as large 

 as 55 to 70 cm (Devincenzi and Teague 1942; Ringuelet et al. 1967). Principal 

 meristics and morphometries of the species are summarized in Tables 24-25. 



Dorsal profile of body smooth, top of head gently sloping from snout to 

 dorsal fin origin. Flesh on top of head relatively thick and not exposing the rigid 

 dorsal neurocranial elements. Supraoccipital and nuchal shield extending as broad 

 plate to dorsal origin. Epaxial musculature of nape and anterior trunk well- 

 developed in larger specimens. Breeding males with swollen epaxial musculature 

 surrounding base of dorsal fin, with slope of dorsal profile over supraoccipital much 

 more convex than in females and non-nuptial males. Head blunt and broad, 27-33% 

 SL in length and 19-25% SL in width. Shape of snout broadly parabolic when 

 viewed from above. Mouth large, weakly inferior, the premaxillaries extending 

 slightly in front of the dentaries. Eyes moderately large (horizontal diameter 

 averaging 10% HL), sublateral, equally visible from below or above. Gill 

 membranes broadly fused to isthmus at plane about even with rear margin of eyes. 

 Gill rakers short, conical, without crenulations on medial margin; first gill arch with 

 3-7 (X = 4.3; N = 21) rakers on outside row of epibranchial, 13-25 (x = 19.8) on 



.,.1 ^ '.- 



