j WUbTWH Problems in catfish anatomy and phylogeny exemplified by the Neotropical Hypophthalmidae (Teleostei: Siluroidei) Gordon J. Howes Department of Zoology, British Museum (Natural History), Cromwell Road, London SW75BD Contents Introduction 1 List of genera examined 3 Form and function in Hypophthalmus and comparison with other siluroids . 4 Body shape, sensory canals and lateral line system 4 The eye and infraorbital bones 6 Cranial musculature . . . . 9 The snout and jaws 17 The cranium 21 The complex vertebrae, swimbladder and posterior lateral line nerve . . 25 The suspensorium 39 The hyoid arch 32 The opercular series 34 The gill arches 34 Postcranial elements 35 Relationships of the Hypophthalmidae 35 Acknowledgements 33 References 38 Introduction Of the subgroups of otophysan fishes, the siluroids or catfishes are the most morpho-logically diverse. None of the other subgroups, gymnotoids, characoids and cyprinoids, has such a range of body shape, peculiarity of dermal covering when present, and cranial morphology. Neither do these groups display such a range of postcranial architecture, complex fusion patterns of the caudal fin skeleton or such diverse forms of swimbladder. This morphological diversity is reflected in the most recent familial classification of the siluroids (Greenwood et al., 1966), which recognises thirty-one families, a number exceeding the combined familial total of other otophysan groups. As presently recognised, most siluroid families are morphologically well differentiated, suggesting that each is probably a monophyletic assemblage. Indeed, the large morphological 'gaps' separating families are emphasised by the fact that seven families are monotypic, cf one among characoids and two among gymnotoids. That the interrelationships of siluroid families have scarcely been studied is not surprising when one considers the paucity of anatomical data available. Even the largest families, i.e. the Pimelodidae, Ariidae and Bagridae are represented in the anatomical literature by only meagre information, the anatomy of some neotropical families, Auchenipteridae, Ageneiosidae, and Aspredinidae, has scarcely been described. The siluroids offer a wealth of character complexes involving the bony elements of the cranium, vertebral column and fin supports, and their associated muscles. These character Bull. Br. Mus. nat. Hist. (Zool.) 45( 1 ) : 1-39 Issued 28 July 1983
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