A new species of Characidium Reinhardt (Characiformes: Crenuchidae) with a unique mid-water behavior from the upper rio Madeira basin, Brazil.

A new species of Characidium is described from headwater tributaries of the upper rio Guaporé, Rio Madeira basin, Mato Grosso state, Brazil. The new species can be diagnosed from all congeners, except Characidium summus, for lacking the preorbital and postorbital stripes. It can be diagnosed from the latter species by having 12 circumpeduncular scales (vs.