The South American killifish genus Pterolebias has been overhauled in a new revisionary study.
World famous killifish expert Wilson Costa of the Department of Zoology at the University of Rio de Janeiro, Brazil, used a combination of colour patterns, bones, external anatomy and the construction of the lateral line sensory system to analyse the relationships of the fishes in the genus.
Costa's findings, which are reported this week in the journal Zootaxa, show that only two of the four members are actually valid species.
Pterolebias longipinnis, the Longfin killi, which was described by Garman in 1895 is a valid species and occurs in the southern and eastern portions of the Amazon basin, as well as the Parana Paraguay system in Brazil, Paraguay, Argentina and Bolivia.
The other valid species, Pterolebias phasianus, described by Costa himself in 1988, is known from the Paraguay basin in Brazil and Bolivia.
Two other members of the genus, P. bokermanni, described by Travossos in 1955, and P. luelingi, described by Meinken in 1969, are both considered synonyms of P. longipinnis.
Other scientists who have undertaken molecular work on these rivuline killifishes have suggested lumping the representatives of Pterolebias in with the species in Gnatholebias. However, Costa rejects this.
Says Costa: "Monophyly of Pterolebias is corroborated by the morphology of the angulo-articular, second pharyngobranchial, maxilla,
metapterygoid, quadrate, basihyal, and two derived color patterns.
"In contrast to molecular studies, monophyly of an assemblage including Pterolebias and Gnatholebias is herein strongly supported by reduction of the interarcual cartilage, morphology of the anterior proximal radials of the anal fin and pelvic girdle, presence of scale rows on the anal-fin base, derived jaw dentition, numerous pelvic-fin rays, and long pelvic fins."
For more details see the paper: Costa, WJEM. (2005) - The Neotropical annual killifish genus Pterolebias Garman (Teleostei: Cyprinodontiformes: Rivulidae): phylogenetic relationships, descriptive morphology, and taxonomic revision. Zootaxa 1067: 1-36 (2005).