Brazilian ichthyologists have described a new species of silver dollar from the upper Paraguay River drainage in a recent issue of the journal Neotropical Ichthyology.
Carla Pavanelli, Rafaela Ota and Paulo Petry name the new species Metynnis cuiaba after its type locality (the Cuiaba River, a tributary of the Paraguay River).
The authors distinguish the new species from congeners by its possession of 100"110 lateral-line scales, 48"56 rows of scales above the lateral line, 32"36 circumpeduncular scales, 22"24 gill rakers, 38 vertebrae, indistinct dark blotches sometimes forming transverse bars on the flanks, and relatively narrower snout and shorter head.
For more information, see the paper: Pavanelli, CS, RP Ota and P Petry (2009) New species of Metynnis Cope, 1878 (Characiformes: Characidae) from the rio Paraguay basin, Mato Grosso State, Brazil. Neotropical Ichthyology 7, pp. 141"146.