A new species of South American killifish that lacks pelvic fins has been described from ccentral Brazil by Wilson Costa and Gilberto Brasil in the latest 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 Melanorivulus in lacking (or having extremely reduced) pelvic fins and girdle, 5"7 vomerine teeth and basihyal width about 70% its length.
The new species is known only from the upper Tocantins River drainage.
According to the authors, pecies of Melanorivulus inhabit sunny aquatic environments, such as shallow pools, canals, and streams, with orange clay bottom, clear water, pH 5.0"6.5.
For more information, see the paper: Costa,WJEM and GC Brasil (2008) A new pelvicless killifish species of the genus Rivulus, subgenus Melanorivulus (Cyprinodontiformes: Rivulidae), from the upper Tocantins River basin, central Brazil. Copeia 2008, pp. 82"85.