Morphological Evidence for the Monophyly of the Subfamily of Parasitic Catfishes Stegophilinae (Siluriformes, Trichomycteridae) and Phylogenetic Diagnoses of Its Genera

The subfamily of Neotropical parasitic catfishes Stegophilinae (Trichomycteridae) is a remarkable group given its specialized feeding habits (lepidophagy, muciphagy, and necrophagy). Despite its biological interest, the systematics of this group has remained in an incipient state. Most genera lack a phylogenetic diagnosis, leading thus to taxonomic instability at that level. Similarly, the hypothesis of monophyly of Stegophilinae is supported by scant morphological evidence. In this study, based on a broad morphological comparative survey of representative genera and species of each subfamily of Trichomycteridae, new evidence is provided to support Stegophilinae as a monophyletic unit. Stegophilinae is herein recognized by four unique synapomorphies, three of them proposed here for the first time. Additionally, phylogenetic diagnoses are offered for all currently recognized genera (including Pareiodon), except Parastegophilus which is placed in the synonymy of Pseudostegophilus. An identification key for stegophiline genera based on external morphology is also presented.