Oligocene killifishes (Teleostei: Cyprinodontiformes) from southern France: relationships, taxonomic position, and evidence of internal fertilization

Abstract

Phylogenetic relationships of five species of Prolebias from the Oligocene of southern France (P. aymardi, P. cephalotes, P. delphinensis, P. meridionalis, and P. stenoura) were examined under an analysis comprising 36 terminal taxa, representing all the main lineages of the order Cyprinodontiformes. It indicated Prolebias as a polyphyletic group, supporting Prolebias stenoura, the type species of the genus, as a valenciid monotypic lineage. Prolebias aymardi and P. delphinensis comprise a new valenciid genus, Francolebias, gen. nov., diagnosed by a unique morphology of pelvic bone, anterior proximal radials of the dorsal fin and anal fins, and hemal spines in putative males. The apomorphic specialized morphology of the anal fin and adjacent vertebrae is interpreted as evidence of an internal fertilization reproductive mode. Prolebias meridionalis is designated as the type species of a new monotypic cyprinodontid genus, Eurolebias, gen. nov., hypothesized to be the sister group to a clade comprising all other cyprinodontids, which is diagnosed by the apomorphic morphology of jaws, parhypural, and absence of parietals. Close relationships between P. cephalotes, P. egeranus from the lower Miocene of Czech Republic, and recent species of the poeciliid genus Pantanodon are corroborated on the basis of the apomorphic morphology of the dentary, pharyngobranchials, pelvic bone, and pelvic-fin rays, justifying the transference of those two species to the latter genus. The present study indicates that the European Oligocene fauna of cyprinodontiform fishes was greatly diversified when compared to its present poor fauna, comprising lineages now extinct or restricted to other continents.