Two new catfish species from central Brazil comprising a new clade supported by molecular phylogeny and comparative osteology (Siluriformes: Trichomycteridae)

The Trichomycterinae is a diversified catfish clade exhibiting numerous ecological specializations, thus offering fine opportunities for studies on vertebrate evolution, but insufficient knowledge on phylogenetic relationships and taxonomy impedes advanced evolutionary studies. Recent studies have contributed to a better taxonomical resolution of some trichomycterine groups, but several taxa remain poorly known, with taxonomical placement still undetermined. This study is directed to two similar undescribed species with unclear generic placement, collected in the savannahs of central Brazil, in the headwaters of the two most important South American river systems, the Amazon and Paraná basins central Brazil. A multigene phylogeny integrated to a comparative osteological analysis supports a clade, with the new species forming a subclade sister to a trichomycterine subclade endemic to southern South America. The comparative osteological analysis provided some characters from the jaw suspensorium, opercular series, branchial arches, neurocranium, and pectoral girdle that are useful to diagnose members of the clade. The two species may be distinguished by meristic data, morphometrics, osteology, and colour pattern. Following recent efforts for a better understanding about diversity and relationships of trichomycterines, the present study provides phylogenetic and morphological basis for the taxonomical resolution of this important trichomycterine clade. However, much more research is necessary to improve trichomycterine taxonomy, including further studies providing a proper generic classification encompassing the whole Trichomycterinae.