152 PROCEEDINGS OF THE NATIONAL MUSEUM ^"^- "^ 



posteriorly beyond vertical from anterior border of orbit. (16) 

 Branchiostegal rays five. (17) Gill membranes partially united but 

 free from isthmus. (18) Body elongate, with blunt head and snout; 

 body rounded in cross section in region of dorsal fin and head, com- 

 pressed in region of caudal peduncle, (19) Adipose fin absent. 

 (20) Anal fin short-based, with about 10 to 12 rays. (21) Dorsal fin 

 always in advance of anal fin, usually over pelvic fins. (22) Caudal 

 fin rounded in profile. (23) Scales moderate to fairly large, about 

 30 to 45 in a lateral series, about 7 to 12 in horizontal rows between 

 dorsal and pelvic fins. 

 The genera of subfamily Erythrininae are : 



Hoplias Gill (1903), with one or two species 



Erythrinus Scopoli (1771), with one species 



Hoplerythrimis Gill (1895), with one species 



Pseuderythrinus Hoedeman (1950b), with one species, status uncertain 



Remarks: Of the characters listed above, 3-8 seem to be diagnostic 

 for the subfamily, distinguishing its members from all other characids. 



Relationships of the Subtribe Naimostomina and its Close 

 Relatives, the Pyrrhulinina 



The classification above clearly indicates the close relationship of 

 the Nannostomina and Pyrrhulinina. The unique structure of the 

 dentary in these two groups, together with the accumulation of such 

 characters as three branchiostegal rays, a premaxillary without a clear 

 upper or lower process, short parietal and epiphyseal laterosensory 

 canals, no supratemporal or dermopterotic canals, no extrascapular 

 bone or canal, no canal embedded in the supracleithrum, and the lack 

 of a frontal-pterotic joint, cannot be due to convergent evolution 

 but only to a common ancestry. Further inspection of these fishes 

 reveals other similarities; for example, their scales are almost identical 

 in shape and structure, both groups have members with modified anal 

 fin rays in the males, both have a tendency to lose canals in orbital 

 bones, and one species, Nannostomus espei, has a color pattern re- 

 markably like that of Pyrrhulina vittata and Pynhulina spilota. 

 Nannostomus espei also has scales that more closely approach the 

 shape of those of Pyrrhulina than the scales of any other species in 

 the Nannostomina. The osteology of Nannostomus espei, however, 

 is typically that of Nannostomus. 



The Nannostomina are specialized for feeding on small animal 

 organisms that occur on plants, rocks, and other objects. They also 

 feed on slowly moving free-living organisms. Their movements are 

 relatively slow and precise. The Pyrrhulinina are more active and 

 more predaceous, having larger mouths, attacking larger prey, and 



