Hemiodus langeanii (Characiformes: Hemiodontidae), a new species from rio Amana, rio Maués-Açú drainage, Amazon basin, Brazil

Abstract

Hemiodus langeanii, new species, is described based on 20 specimens collected in the rio Amana, a tributary of rio Maués-Açú, rio Amazonas drainage, Brazil. The new taxon can be distinguished from its congeners by its high body (27.1-35.3%, average 32.3% SL vs. 18.8-28.5% in remaining species). The new species also exhibits a large lateral dark spot that is equal to, or greater than, the eye diameter (vs. smaller in remaining species except for H. microlepis). The lack of conspicuous lateral stripe or transverse bands and the low lateral line scales count (68-74) distinguish H. langeanii from some similar species in the genus (scale counts: 94-123 in H. argenteus, 124-148 in H. microlepis, 86-99 in H. orthonops and 77-92 in H. parnaguae). Finally, the new species can be differentiated from H. unimaculatus (which overlaps in the number of lateral line scales) by the higher number of scales between the lateral line and the pelvic fin origin (9-10 vs. 4-7, respectively), which are similar sized above and below lateral line (vs. scales larger bellow the lateral line in H. unimaculatus). © 2012 Sociedade Brasileira de Ictiologia.