THE SYSTEMATICS, DISTRIBUTION, AND ZOOGEOGRAPHY OF THE MARINE HATCHETFISHES (FAMILY STERNOPTYCHIDAE) RONALD CLAY BAIRD' TABLE OF CONTENTS Introduction 2 Methods 3 Osteological Character Complexes 7 Osteological Conckisions 15 The Fossil Record 22 Systematics 29 Family Stemoptychidae 29 Key to the genera of Stemoptychidae 29 Genus Argyropelectis 31 Key to the species of Argijropelecus 32 Argyropelectis affinis 34 Argyropeleciis gigas 38 Argyropdecus hemigymniis 42 Argyropeleciis aculeatus 48 Argyropelecus olfersi 52 Argyropeleciis sladeni 56 Argyropelecus lynchus -. 63 C^enus Sternopiyx 67 Key to the species of Sternoptyx 68 Stcrnoptyx ohscura 69 Sternoptyx pseudobscura 72 Sternoptyx diaphana 75 Genus Polyipnus 79 Key to the species of Polyipnus ^ 82 Polyipnus tridentifer 86 Polyipnus sterope 88 Polyipnus spinosus 89 Polyipnus oluolus 90 Polyipnus indicus 91 Polyipnus niittingi 92 Polyipnus laternatus 92 Polyipnus oniphus 94 Polyipnus aquavitus 96 Polyipnus iinispinus 97 Polyipnus triphanos 97 ^ Museum of Comparative Zoology, Hai"vard Uni-versity, and Marine Science Institute, University of South Florida, St. Petersburg, Fla. 33701. Polyipnus polli 98 Polyipnus asteroides 99 Polyipnus matsuharal 101 Polyipnus ruggcri 102 Polyipnus kiiviensis 103 Polyipnus meteori 104 Discussion and Conclusions 104 Patterns of Distrilaution 104 Geographic Variation 106 Distributional Factors 107 Zoogeographic Regions 110 Acknowledgments 1 14 Summary 115 Appendix A ^ 115 Appendix B 117 Literature Cited 123 ABSTRACT The systematic history of tlie Stemoptychidae has been one of instability in higher classification. A study of comparative osteology indicates that die hatchetfishes are closely related to the Gonosto-matidae but differ from them in certain significant aspects. The Stemoptychidae are therefore given familial rank. Fossil evidence indicates that the family prob-ably arose during the early Tertiary and reached its present evolutionary grade by the middle Miocene. Three phylogenetically divergent genera are recog-nized, these being Argyropelecus, Polyipnus, and Sternoptyx, with seven, seventeen, and three species respectively. Many species exhibit geographical variation and morphologically distinct populations were defined in some instances. The genera differ broadly in habitat as well as morphology. Argyropelecus is a high seas pelagic genus limited to the upper 600 m. Sternoptyx shows a similar pattern horizontally but inhabits the 500 to 1500 m depth zone. Polyipnus occurs only in close association with land, exhibiting a chstribu-tion and speciation pattern similar to many tropical shore species. Argyropelecus and Sternoptyx spe-Bull. Mus. Conip. Zool., 142(1): 1-128, October, 1971
BioStor
