Integrative Taxonomy Reveals a New Species of Imparfinis (Siluriformes: Heptapteridae) from the Upper Xingu River Basin

Imparfinis is a genus of small catfishes with 21 valid species broadly distributed throughout the main river basins of the Neotropical region. Here, a new species of Imparfinis is described from the headwaters of the Rio Xingu. The new species is distinguished from its congeners by the presence of a wide dark stripe from snout tip to caudal peduncle sharply contrasting pale underside and aligned with dark stripe centered on dorsal portion of lower caudal-fin lobe, 1112 gill rakers on the first ceratobranchial, 39 vertebrae, maxillary barbel surpassing vertical through dorsal-fin origin, and absence of short, flexible extension of the anteriormost pectoral, dorsal, and upper caudal-fin rays. In addition, assemble species by automatic partitioning (ASAP) and the Poisson tree processes model (bPTP) analyses support the validity of this new species. Our molecular phylogeny based on the cytochrome c oxidase subunit 1 mitochondrial gene (COI) corroborates the placement of the new species in Imparfinis and its close relationship with I. guttatus. Species delimitation in Imparfinis is discussed.