Anatomy and phylogenetic analysis of the neotropical callichthyid catfishes (Ostariophysi, Siluriformes)

Based mainly on morphological characters, the phylogenetic relationships among genera and some species groups of the neotropical family Callichthyidae were examined. A study of the osteology of a generalized callichthyid, Callichthys callichthys (Linnaeus), with detailed comparisons among representatives of the remaining genera in the family, is presented and used as a basis for the phylogenetic analysis. A single most parsimonious tree supported the monophyly of the family Callichthyidae based on 28 derived features and the division of the family in the subfamilies Corydoradinae and Callichthyinae. In the subfamily Corydoradinae, the genus Aspidoras is the sister-group of the clade formed by Corydoras plus Brochis. Five derived features support the monophyly of this clade and four support the monophyly of Brochis. No characters, however, were found to support the genus Corydoras. In the subfamily Callichthyinae, Dianema and Hopbstemum are sister-taxa. Megalechis represents the sister-group of Dianema plus Hoplosternum and Lepthoplosternum represents the sister-group to Megalechis plus Dianema plus Hopbstemum. Finally, Callichthys is considered the least derived member of the subfamily, and is hypothesized as the sister-group of the remaining species. A key to all callichthyid genera is provided.