Characidium serrano Buckup & Reis, 1997 (fig. 3)

Morphometric data are given in table 1. Premaxillary teeth 7-8; dentary teeth 9-10. Lateral line scales 36. Scale rows above lateral line 4-5 and below 3. Scales in predorsal series 11-13. Scales around caudal peduncle 12. Dorsal-fin rays iii,9. Pectoral-fin rays i,9-i,11. Anal-fin rays ii, 6.

Characidium serrano is known from the rio Jacutinga, upper río Uruguay basin in Santa Catarina State, Brazil. The specimens of C. serrano reported on herein were collected in the arroyo Shangay, middle río Uruguay basin and arroyo Toro, upper río Uruguay basin in Misiones province, Argentina (figs. 1, 4).

Material examined: MLP 10751, 1 ex., 51.7 mm SL, río Uruguay basin, Misiones province, arroyo Shangay (27°28'13.8" S, 54°41'24.5" W), December 2007 . MLP 10752, 2 ex., 46.6-51.7 mm SL, río Uruguay basin, Misiones Province, arroyo Toro (26º36ʹ32.81ʺ S, 53º44ʹ13.97ʺ W), February 2012 .