The world's smallest vertebrate species of the genus Paedocypris: A new family of freshwater fishes and the sister group to the world's most diverse clade of freshwater fishes (Teleostei: Cypriniformes)

The genus Paedocypris has only recently been discovered and described and includes three species, all of which are miniature species and one, P. progenetica, is the smallest vertebrate species. Two previous studies investigating relationships of Paedocypris, based on either cytochrome b or morphology, placed the genus with Sundadanio and Danionella, two genera with miniature species in the formerly recognized family Cyprinidae. Our investigation of the phylogenetic relationships of Paedocypris using six nuclear genes and a broad survey of taxa in major lineages of the Cypriniformes identifies Paedocypris as a monophyletic group and the basal sister group to all Cypriniformes, not a species of the formerly recognized family Cyprinidae. These new relationships are also supported by previously proposed morphological characters but reinterpreted relative to ontogenetic hypotheses and outgroup comparisons used to determine synapomorphies. Miniaturization has occurred independently multiple times in the order, but mostly in the Rasborine Cade. Consequently, the hypothesis of a shared ancestral developmental truncation of multiple morphological features in genera with miniature species is rejected. While strong evidence exists for the new phylogenetic placement of Paedocypris as the sister group to the most diverse clade of freshwater fishes attempts to theorize more broadly as to evolutionary processes of miniaturization would be premature without more complete taxon sampling. Accompanying growing consistency of phylogenetic evidence of relationships in the Cypriniformes has come the consistent support of major clades within the previously recognized family Cyprinidae now recognized as a series of separate families, rendering the former Cyprinidae equivalent to Cyprinoidea. The revised family Cyprinidae includes species of the former subfamily Cyprininae, sister to Psilorhynchidae. The former subfamilies of Cyprininae, Acheilognathinae, Leuciscinae, and Gobioninae are elevated to families, and in keeping with consistency between phylogenetic relationships and classification the families Leptobarbidae and Tincidae are now recognized and the new families Tanichthyidae and Sundadanionidae are described. Paedocypris is recognized in a new superfamily, Paedocypridoidea, and family, Paedocyprididae. (C) 2010 Elsevier Inc. All rights reserved.