On two new genera of Trichomycteridae (Teleostei, Siluriformes), with reallocation of some previously described taxa and discussion of phylogenetic relationships

Abstract

Two new genera are established for resolving some obvious disparities in current trichomycterid classification. Salpynx is described for a monophyletic group of four species from northern shield regions of the Amazon basin, including two new ones described herein plus two others previously described: S. ephebus, new species, from Serra da Mocidade in the Rio Branco system, S. trombetensis, new species, from the Rio Trombetas drainage, S. amapaensis (previously in Ammoglanis) from the Rio Jari and surrounding basins, and S. ix (previously in Stenolicmus) from the Rio Trombetas. Species of Salpynx are opaque darkly pigmented fishes with an entirely closed skull roof (i.e., no cranial fontanels) and apomorphically diagnosed by a thick barbular bone posteriorly expanded and bilobed, and a large fenestra on the supratemporal region of the skull, anteriorly to the tunnel for the dorsal limb of the cleithrum. A second new genus, Hyaloglanis, is established for a clade of miniaturized species previously placed in Ammoglanis, namely, A. natgeorum, A. nheengatu, A. obliquus, and A. pulex. Hyaloglanis species are extremely miniaturized and highly translucent, with a single large fontanel occupying most of the skull roof and sharing an apomorphic scythe-shaped lacrimal. Salpynx and Hyaloglanis share various unusual conditions in trichomycterids, such as a reduction of the latero-sensory canal system in the skull, which anteriorly extends maximally to the sphenotic, a palatine articulating directly posteriorly with the skull and via a single articular facet, the posterolateral process of the palatine reduced and deflected laterally, lateral ethmoids mesially arched and abuting against each other only at a small area anteriorly, and a long filamentous first pectoral-fin ray. Although clear morphological evidence exists for the monophyly each of Salpynx and Hyaloglanis, difficulties remain in determining their precise phylogenetic placement. Such limitations highlight current challenges in the resolution of relationships of part of the Trichomycteridae, especially concerning Glanapteryginae (including Listrura), Potamoglanis, and Sarcoglanidinae Sarcoglanidinae (including Microcambeva). It seems certain, however, that neither Salpynx nor Hyaloglanis are closely related to the type species of either Ammoglanis or Stenolicmus. At the moment, morphological evidence favors them as each other’s sister group and related to Glanapteryginae (sensu lato).