Cnesterodon raddai Meyer & Etzel, 2001

(Fig. 4)

Cnesterodon raddai Meyer & Etzel, 2001: 248, fig. 1

( holotype, male); 2 (paratype, female); 3 (gonopodium) & 4 (aquarium specimen, male). Type -locality: swamp near Resistencia, Rio Paraná basin, Argentina .

Diagnosis. Cnesterodon raddai is diagnosed by the following autapomorphies: (1) the small number (one to four) of patches of dark pigmentation along flanks; (2) minute size of adults; (3) predorsal line absent; (4) three pelvic-fin rays in males [33-3]. Cnesterodon raddai further differs from its congeners by: (1) pleural ribs in adult males not curved forward converging to the same point towards pelvic girdle [59-0]; and (2) anterior and posterior orbital bony plates present [143- 1].

In addition, C. raddai differs from its congeners, but C. omorgmatos, by the circular or irregular dark brown blotches along body sides. Cnesterodon raddai is distinguished from C. omorgmatos by the general size of adults (14.6-17.0 mm [adult males], 17.1-23.2 mm [adult females] vs. 18.7-24.8 mm [adult males], 20.0- 30.5 mm [adult females], respectively) and by its color pattern (one to four clearly rounded dark spots or wide and short bars along flanks vs. six to nine dark brown circular to irregular blotches or vertical wide bars along body sides, respectively).

Distribution. Cnesterodon raddai is distributed in the rio Paraguay and lower rio Paraná drainages.