Zoological Journal of the Linnean Society (1998), 124: 105–168. With 37 figures Article ID: zj970127 Anatomy and phylogenetic analysis of the neotropical callichthyid catfishes (Ostariophysi, Siluriformes) ROBERTO E. REIS Laborato ´rio de Ictiologia, Museu de Cie ˆncias e Tecnologia – PUCRS, Av. Ipiranga, 6681, Caixa Postal 1429, 90619-900 Porto Alegre, RS, Brasil Received March 1996; accepted for publication July 1997 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 Hoplosternum are sister-taxa. Megalechis represents the sister-group of Dianema plus Hoplosternum and Lepthoplosternum represents the sister-group to Megalechis plus Dianema plus Hoplosternum. 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.  1998 The Linnean Society of London ADDITIONAL KEY WORDS:—South America – biogeography – Loricarioidei – Cal- lichthyidae – phylogeny – Teleostei. CONTENTS Introduction . . . . . . . . . . . . . . . . . . . . . . . 106 Material and methods . . . . . . . . . . . . . . . . . . . 109 Abbreviations . . . . . . . . . . . . . . . . . . . . . . 110 Osteology of Callichthys callichthys . . . . . . . . . . . . . . . . 111 Description . . . . . . . . . . . . . . . . . . . . . . . 112 Neurocranium . . . . . . . . . . . . . . . . . . . . 112 Latero-sensory canals . . . . . . . . . . . . . . . . . . 119 Infraorbital series . . . . . . . . . . . . . . . . . . . 122 Suspensorium and mandibular arch . . . . . . . . . . . . . 122 Opercular series . . . . . . . . . . . . . . . . . . . . 125 Hyoid arch . . . . . . . . . . . . . . . . . . . . . 126 Branchial arches . . . . . . . . . . . . . . . . . . . . 127 Weberian apparatus and axial skeleton . . . . . . . . . . . . 128 105 0024–4082/98/100105+64 $30.00/0  1998 The Linnean Society of London