Three new species of the killifish genus Melanorivulus from the Rio Parana Basin, central Brazilian Cerrado (Cyprinodontiformes, Aplocheilidae)

Three new species of Melanorivulus are described from the upper and middle Rio Parana Basin, central Brazilian Cerrado. These species are members of the M. pictus species group, endemic to central Brazilian plateaus and adjacent areas, and are easily diagnosed by colour pattern characters, but their relationships with other congeners of the group are still uncertain. Melanorivulus proximus sp. n., from the middle Rio Apore drainage, and M. nigromarginatus sp. n., from the Rio Corrente drainage, are possibly more closely related to other species endemic to streams draining the slopes of the Caiapo range, whereas M. linearis sp. n., from the upper Rio Pardo drainage, middle Rio Parana Basin, is considered more closely related to M. egens, a species also endemic to this part of the Basin. This study corroborates the high diversity of species of Melanorivulus in the central Brazilian Cerrado plateaus repeatedly reported in previous studies, indicating once more that different species are often found restricted to short segments of the same river drainage. The intense habitat loss recorded in recent years combined to the high species diversity limited to specific Cerrado freshwater ecosystems, the veredas, indicates that species of Melanorivulus endemic to this part of the Brazilian Cerrado are highly threatened with extinction.