The Neotropical Fish Family Chilodontidae (Teleostei: Characiformes): A Phylogenetic Study and a Revision of Caenotropus Gunther RICHARD P. VARI, RICARDO M.C. CASTRO. and SANDRA J.RAREDON i SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 577 SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTION Emphasis upon publication as a means of "diffusing knowledge" was expressed by the first Secretary of the Smithsonian. In his formal plan for the institution, Joseph Henry outlined a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This theme of basic research has been adhered to through the years by thousands of titles issued in series publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Contributions to Anthropology Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to the Marine Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Folklife Studies Smithsonian Studies in Air and Space Smithsonian Studies in History and Technology In these series, the Institution publishes small papers and full-scale monographs that report the research and collections of its various museums and bureaux or of professional colleagues in the world of science and scholarship. The publications are distributed by mailing lists to libraries, universities, and similar institutions throughout the world. Papers or monographs submitted for series publication are received by the Smithsonian Institution Press, subject to its own review for format and style, only through departments of the various Smithsonian museums or bureaux, where the manuscripts are given substantive review. Press requirements for manuscript and art preparation are outlined on the inside back cover. I. Michael Heyman Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 577 The Neotropical Fish Family Chilodontidae (Teleostei: Characiformes): A Phylogenetic Study and a Revision of Caenotropus Giinther Richard P. Vari, Ricardo M.C. Castro, and Sandra J. Raredon SMITHSONIAN INSTITUTION PRESS Washington, D.C. 1995 ABSTRACT Vari, Richard P., Ricardo M.C. Castro, and Sandra J. Raredon. The Neotropical Fish Family Chilodontidae (Teleostei: Characiformes): A Phylogenetic Study and a Revision of Caenotro- pus Giinther. Smithsonian Contributions to Zoology, number 577,32 pages, 20 figures, 5 tables, 1995.—A series of synapomorphies for the characiform family Chilodontidae, in addition to those proposed by Vari (1983), are discussed. These involve modifications of the suspensorium, hyoid arch, infraorbitals, lower jaw, supraorbital portion of the laterosensory canal system in the frontal, and lateral-line scales. The chilodontid genera Chilodus Miiller and Troschel (1844) and Caenotropus Giinther (1864) are diagnosed as monophyletic on the basis of derived features of the third postcleithrum, lower jaw, hyoid arch, pterotic, supracleithrum, and the laterosensory canal systems in the infraorbitals, frontal, and posterior lateral-line scales. Modifications of a subset of those systems, the subopercle, dentition, suspensorium, third postcleithrum, and pigmentation define subunits of Caenotropus or are autapomorphic for its species. Caenotropus is revised, with Tylobronchus Eigenmann (1912) considered a junior synonym. Three Caenotropus species are recognized: C. labyrinthicus (Kner, 1858) widely distributed in the Rio Amazonas and Rio Orinoco basins, the upper Essequibo River basin in Guyana, the Saramacca and Suriname Rivers in Suriname, and the Rio Parnafba, northeastern Brazil; C. maculosus (Eigenmann, 1912) ranging from the Essequibo River of Guyana to the Fleuve Maroni of French Guiana; and C. mestomorgmatos, new species, from the acidic black waters of the middle and upper Rio Negro in Brazil and Venezuela and the upper Rio Orinoco in southern Venezuela. Chilodus labyrinthicus rupununi Fowler (1914) is placed into the synonymy of Caenotropus labyrinthicus. Keys are provided to the genera Caenotropus and Chilodus and to the species of Caenotropus. A lectotype is designated for Microdus labyrinthicus Kner. The biogeographic implications of the geographic distribution of subunits of the Chilodontidae are discussed. 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 Vari, Richard P. The neotropical fish family Chilodontidae (Teleostei: Characiformes) : a phylogenetic study and a revision of Caenotropus Gtinther / Richard P. Vari, Ricardo M.C. Castro, and Sandra J. Raredon. p. cm. — (Smithsonian contributions to zoology ; no. 577) Includes bibliographical references (p. 30) and index. 1. Chilodontidae—Classification. 2. Caenotropus—Classification. 3. Chilodus—Classifica- tion. 4. Caenotropus—South America—Geographical distribution. I. Castro, Ricardo M. C. II. Raredon, Sandra J. III. Tide. IV. Series. QL1.S54 no. 577 [QL638.C544] 591 s—dc20 [597'.52] 95-32787 ® 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. Contents Page Introduction 1 Acknowledgments 1 Methods and Materials 2 Institutional Abbreviations 2 Text and Figure Abbreviations 3 Character Description and Analysis 3 Infraorbital Series 3 Second and Third Infraorbitals 3 Fourth and Fifth Infraorbitals 4 Sixth Infraorbital 4 Subopercle 4 Supraorbital Laterosensory Canal 4 Pterotic 5 Jaw Dentition 5 Lower Jaw 5 Hyoid Arch 6 Dorsal and Ventral Hypohyals 6 Dorsal Hypohyal and Anterior Ceratohyal 7 Mesopterygoid 7 Metapterygoid and Quadrate 7 Supracleithrum 8 Third Postcleithrum 8 Laterosensory Canal System on Body 9 Pigmentation 10 Synapomorphy List and Phylogenetic Reconstruction 10 Monophyly of the CHILODONTIDAE 10 Monophyly of Chilodus 11 Monophyly of Caenotropus 11 Intrageneric Relationships in Caenotropus 11 Family CHILODONTIDAE 12 Key to Caenotropus Giinther and Chilodus Miiller and Troschel 12 Genus Caenotropus Giinther, 1864 12 Key to the Species of Caenotropus Giinther 13 Caenotropus mestomorgmatos, new species 14 Caenotropus maculosus (Eigenmann, 1912) 17 Caenotropus labyrinthicus (Kner, 1858) 21 Phylogenetic Biogeography of the CHILODONTIDAE 28 Resumo 29 Literature Cited 30 Index 32 in The Neotropical Fish Family Chilodontidae (Teleostei: Characiformes): A Phylogenetic Study and a Revision of Caenotropus Giinther Richard P. Vari, Ricardo M.C. Castro, and Sandra J. Raredon Introduction Caenotropus Giinther (1864). In a familial-level phylogenetic analysis, Vari (1983:51-52) listed twenty-six synapomorphies The external appearance of the members of the Neotropical common to Chilodus and Caenotropus but did not delve into characiform family Chilodontidae provides little indication of the questions of the monophyly or the recognizable species in the extensive and unusual internal modifications that character- each genus. Chilodus was revised subsequently by Isbriicker ize the family (Vari, 1983:51-52). Numerous restructurings of and Nijssen (1988) who recognized three species, C. punctatus bones, cartilages, and soft tissues are associated with the highly Muller and Troschel (1844), C. zunevei Puyo (1945), and C. modified gill-arches and epibranchial organs. The series of gracilis Isbriicker and Nijssen (1988), but they did not attempt distinctive modifications of the axial skeleton, anterior ribs, to determine whether the three species constitute a mono- and associated ligamentous tissues may be correlated, in turn, phyletic group. Caenotropus has not been revised recently, and with the unusual head-down orientation assumed by chilodon- neither the number of species in the genus nor their tids while swimming and resting; a habit reflected in their interrelationships were known. common name of "head-standers." Chilodontids are broadly distributed east of the Andean Cordilleras in the Orinoco and This paper has five aims: (1) to test further the hypothesis of Amazon river basins, the series of independent rivers draining the monophyly of the Chilodontidae; (2) to determine whether the Guianas, and the Rio Parnaiba basin of northeastern Brazil. Chilodus and Caenotropus are monophyletic; (3) to determine The family is unknown in the remaining rivers of the Atlantic the recognizable species of Caenotropus and their geographic slopes of South America or the trans-Andean portions of the distribution; (4) to develop a hypothesis of phylogenetic continent relationships in Caenotropus; and (5) to determine what the Recent authors (e.g., Gery, 1964,1977) have recognized two information about the phylogeny and distribution of chilodon- chilodontid genera, Chilodus Muller and Troschel (1844) and tids tells us about the biogeographic history of the family. ACKNOWLEDGMENTS.—We are indebted to the following individuals and institutions for the loan and exchange of Richard P. Vari and Sandra J. Raredon, Department of Vertebrate specimens, information, hospitality during visits, and other Zoology, National Museum of Natural History, Smithsonian Institu- assistance: Gareth J. Nelson, C. Lavett Smith, M. Norma tion, Washington,