A new species of South American killifish lacking pelvic fins has been described by Wilson Costa and Gilberto Brasil in a recent issue of the journal Copeia. The new species is named Rivulus planaltinus, from the Portuguese name for the county where the type locality is located (Planaltina means from the high plains), and is a member of the Melanorivulus subgenus.

Rivulus planaltinus is distinguished from other members of the subgenus Melanorivulus in lacking (or having extremely reduced) pelvic fins and girdle, numerous vomerine teeth and a wide basihyal.

The new species is known only from the upper Tocantins River drainage. According to the authors, “species of Melanorivulus inhabit sunny aquatic environments, such as shallow pools, canals, and streams, with orange clay bottom, clear water, pH 5.0–6.5. They are often found in the Veredas, streams dominated by the buriti-palm Mauritia flexuosa, typical of the savanna-like Brazilian Cerrado.”

For more information, see the paper: Costa,W.J.E.M., Brasil, G.C.. 2008. A new pelvicless killifish species of the genus Rivulus, subgenus Melanorivulus (Cyprinodontiformes: Rivulidae), from the upper Tocantins River basin, Central Brazil. Copeia 1, 82–85.