Monophyly and Phylogenetic Diagnosis of the Family Cetopsidae, with Synonymization of the Helogenidae (Teleostei: Siluriformes)

de Pinna, Mdrio C.C., and Richard P. Vari. Monophyly and Phylogenetic Diagnosis of the Family Cetopsidae, with Synonymization of the Helogenidae (Teleostei: Siluriformes). Smithsonian Contributions to Zoology, number 571, 26 pages, 20 figures, 1995.—The Neotropical catfishes currently recognized as the families Cetopsidae and Helogenidae are hypothesized to be sister groups. The two taxa share numerous synapomorphies, including a lap joint between the opercle and interopercle, a dorsal displacement of the attachment of the interoperculo-mandibular ligament on the interopercle, and a strongly depressed palatine. Some of these derived characters are unique within Siluriformes. On the basis of this hypothesis of relationships, cetopsids and helogenids are united into an expanded Cetopsidae, itself subdivided into the monophyletic subfamilies Cetopsinae and Helogeninae. The Cetopsinae is synapomorphically diagnosable by, among other characters, an expanded and often ramified cartilaginous posterior process of the basipterygium, an anterior curvature of the third epibranchial, and the articulation of the palatine with the neurocranium only by means of its anterior cartilage. Synapomorphies supporting the monophyly of the Helogeninae include a reduction in the degree of ossification between the mesethmoid cornua and the remainder of the neurocranium, a large paired fontanel in frontal and sphenotic, the posterior expansion of the third basibranchial, and the lack of contact of the sphenotic with the supraoccipital. Phylogenetic diagnoses are provided for the redefined Cetopsidae, Cetopsinae, and Helogeninae. The external morphology of juvenile Helogenes and a number of unusual juvenile features, possibly unique to the genus, are described for the first time. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging-in-Publication Data Pinna, Mario C.C. de. Monophyly and phylogenetic diagnosis of the Family Cetopsidae, with synonymization of the Helogenidae (Teleostei: Siluriformes) / Mario C.C. de Pinna and Richard P. Vari. p. cm. — (Smithsonian contributions to zoology ; no. 571) Includes bibliographic references. I. Cetopsidae—Classification. 2. Cetopsidae—Phylogeny. 3. Helogeneidae—Classification. I. Van, Richard P. II. Series. QL1.S54 no. 571 [QL638.C37) 591 s-dc20 [597'.52] 94-48553 ® The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48—1984.