A new subfamily of Trichomycteridae (Teleostei, Siluriformes), lower loricarioid relationships and a discussion on the impact of additional taxa for phylogenetic analysis

The Copionodontinae is described as a new subfamily of the neotropical catfish family Trichomycteridae. It comprises two new genera and three new species from north-eastern Brazil: Copionodon gen. nov. (including C. pecten sp. nov. and C. orthiocarinatus sp. nov.) and Glaphyropoma gen nov. (including G. rodriguesi sp. nov.) The Copionodontinae can be diagnosed externally by the anterior position of the dorsal fin, the presence of a well-developed adipose fin, and the strongly spatulate shape of the jaw teeth. The subfamily is hypothesized as monophyletic on the basis of several synapomorphies in internal and external anatomy. Copionodontines have the plesiomorphic condition of several characters, relative to all other trichomycterids, including the presence of ductus pneumaticus; the possession of separate pterosphenoids, sphenotics and prootics; the presence of the intercalarium; the complete infraorbital latero-sensory canal; the presence of the interhyal; and the wide lateral opening of the swimbladder capsule. Elsewhere within trichomycterids, these primitive traits are found only in Trichogenes. These and other characters support the hypothesis that copionodontines are the plesiomorphic sister group of all other trichomycterids, and that Trichogenes is their next successive sister group. Contrary to the currently accepted hypothesis, the monotypic Nematogenyidae is proposed as the sister group of the Trichomycteridae, and not of all remaining loricarioids. This change is to a major extent induced by the inclusion of copionodontines and Trichogenes in the analysis of lower loricarioid relationships. The present case is given as an example of the impact that undiscovered taxa, fossil or Recent, may have upon hypotheses of phylogenetic relationships.