THE RELATIONSHIPS AND TAXO- NOMIC POSITION OF THE HALFBEAKS, KILLIFISHES, SILVERSIDES, AND THEIR RELATIVES DONN ERIC ROSEN BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 127 : ARTICLE 5 NEW YORK: 1964 THE RELATIONSHIPS AND TAXONOMIC POSITION OF THE HALFBEAKS, KILLIFISHES, SILVERSIDES, AND THEIR RELATIVES DONN ERIC ROSEN Assistant Curator, Department of Ichthyology The American Museum of Natural History BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 127 : ARTICLE 5 NEW YORK 1964 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Volume 127, article 5, pages 217-268, figures 1-23, plates 14, 15 Issued August 31, 1964 Reprinted June 30, 1973 Price: $1.50 a copy INTRODUCTION THE KILLIFISHES, OR CYPRINODONTIFORMS, order was enlarged by Regan (191 la) to con- are small fresh- and brackish-water fishes of tain the very different North American cave- worldwide distribution in tropical and tem- fishes, later treated by Myers (1931) as a perate latitudes. The largest species attains suborder, the Amblyopsoidei. In 1913 Regan a length of a little over 200 mm., but most described the first known phallostethid and are less than half of that size. With a few ex- assigned it to the cyprinodontoid section of ceptions, they are soft-rayed fishes with cy- the Cyprinodontiformes, but the phalloste- cloid scales, thoracic, subabdominal, or ab- thids were stated by Myers (1928) to be a spe- dominal pelvics, pectorals high on the sides, cialized offshoot of an ancient atherinid an emarginate or rounded caudal, a lateral stock (order Mugiliformes). Also in 1913 line reduced to a series of unconnected pits on Weber described Adrianichthys kruyti and the midlateral scale row, and a hyoid and assigned it to its own family in the Beloni- branchiostegal apparatus of acanthoptery- formes because it possesses the chief ordinal gian type (Hubbs, 1919). In the earliest character of that group. But an allied genus, taxonomic treatment of the Cyprinodonti- Xenopoecilus, had previously been erected by formes, they were regarded as a distinct Regan (191lb) and included in the killifish group allied to or included with the Cyprin- family Cyprinodontidae. Recognizing the idae (see Garman, 1895). Gill, who was re- familial relationship of Adrianichthys with sponsible for the term Cyprinodontes (1865), Xenopoecilus, Weber and de Beaufort (1922) gathered together the cyprinodontiforms and transferred the enlarged Adrianichthyidae to the esocoid fishes (1874) in an alignment that the Cyprinodontiformes, where it has since became known as the Haplomi. It was from remained almost forgotten in the Cyprino- the Haplomi that Regan (1909) extracted dontoidei. the cyprinodontiforms and assigned them Until 1962 the composition of the order ordinal rank as the Microcyprini, although he Cyprinodontiformes was unchanged. At the still accepted their relationships to the eso- time the Cyprinodontoidei consisted of seven coid fishes. Earlier, Boulenger (1904) had families (Cyprinodontidae, Goodeidae, suggested an affinity between cyprinodonti- Jenynsiidae, Anablepidae, Poeciliidae, Hora- forms and beloniforms (synentognaths). At ichthyidae, and Adrianichthyidae), and the this time it was not uncommon for the beloni- Amblyopsoidei of a single family (Ambly- forms and mugiliforms (Percesoces) to be opsidae). In that year Rosen presented evi- either included in a single taxon or at most dence which indicates a relationship of the narrowly separated, and out of this relation Amblyopsidae with the percopsiform genera grew the idea that the cyprinodontiforms and and, more distantly, with the Gadiformes. mugiliforms also are related. Jordan and He isolated the cavefishes as an order, the Evermann (1896), for example, had remarked Amblyopsiformes, and recommended its that the Synentognathi are " . allied to alignment near the Percopsiformes and Gadi- the Haplomi on the one hand and to the formes in a phyletic sequence. Gosline (1963), Percesoces on the other, and like those groups, however, thought that the Amblyopsidae [they mark) the transition from the soft-rayed should be retained as a suborder of the Cyprin- to the spiny-rayed fishes. In their anatomical odontiformes and that the order should be characters the Synentognathi most resemble further enlarged to include also the percopsi- the latter."At various other times the cyprino- form genera, but no firm recommendations dontiforms were compared with the gasteros- were made. Gosline believed that the cyprin- teiforms (including the syngnathiforms), the odontoid killifishes could conceivably have Channiformes, and the Anabantoidei. been derived from an amblyopsid-like an- The composition of the order Cyprino- cestor, but much of the osteological and myo- dontiformes has been somewhat less fluid. logical evidence at variance with this view Originally established to include only the was not considered. cyprinodontoid or typical killifishes, the The idea for the investigation reported 219 220 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY VOL. 127 herein was conceived following an initial (including the Mugilidae), "sphyraenoid" osteological analysis of the adrianichthyid (=Sphyraenoidei, and including the Sphy- fishes. The Adrianichthyidae were found to raenidae), and "polynemoid" (= Polynemi- have a mixture of beloniform, cyprinodonti- formes or Polynemoidei, and including the form, and mugiliform features, and the initial Polynemidae). investigation was therefore broadened to in- Various other teleost groups are discussed clude representatives of all these groups as in customary taxonomic phraseology. well as a species of phallostethid. The specific The specimens examined in this study are objectives of this report are to present a num- given in the Appendix. ber of new considerations on the relation- ships and taxonomic position of the Beloni- ABBREVIATIONS USED IN ILLUSTRATIONS formes, Cyprinodontiformes, and Mugili- A, adductor mandibulae muscle formes, and secondarily to define further the AAP, adductor arcus palatini muscle phylogenetic separation of the cyprinodon- ACT, actinost or radial toid killifishes from the assemblage that in- ANG, angular cludes the Amblyopsiformes and Percopsi- ART, articular formes. BB, basibranchial In any study that involves taxonomic re- BOC, basioccipital CB, ceratobranchial arrangements, inevitably there arises the CH, ceratohyal question of what to call various groups during CL, cleithrum the presentation of new evidence, especially CO, coracoid when new group names are proposed and when DN, dentary groups of long standing are dismembered and DO, dilatator operculi muscle the components are redistributed. In order to DSPH, dermosphenotic minimize herein possible confusion from EB, epibranchial these sources, various equivalences are estab- ECT, ectopterygoid lished. EH, epihyal The terms "Beloniformes," "Cyprinodonti- ENT, entopterygoid (mesopterygoid) EOC, exoccipital formes," and "Mugiliformes" are not used EP, epiotic except in historical contexts. ETH, ethmoideum Substituting for the term "Beloniformes" FR, frontal are the vernacular names "exocoetoid" GH, glossohyal (= Exocoetoidei, and including the Hemi- HB, hypobranchial ramphidae and Exocoetidae), and "scomber- HH, hypohyal esocoid" (=Scomberesocoidei, and including HYO, hyomandibular the Belonidae and the Scomberesocidae). IF, inferior pharyngeal tooth plate Substituting for the term "Cyprinodonti- IH, interhyal formes" are the vernacular names "adrianich- IOP, interoperculum LAC, lachrymal thyoid" (including the Oryziatidae, a new LAP, levator arcus palatini muscle family group name for the genus Oryzias, see LAT, lateral ethmoid below, the Adrianichthyidae, and question- MET, metapterygoid ably the Horaichthyidae) and "cyprinodon- MX, maxilla toid" (including the Cyprinodontidae, Good- NA, nasal eidae, Jenynsiidae, Anablepidae, and Poecili- OP, operculum idae). PA, parietal Substituting for the term "Mugiliformes" PAL, palatine (autopalatine with or without are the vernacular names "atherinoid" (in- dermopalatine) cluding the PAS, parasphenoid Atherinidae, Melanotaeniidae, PASA, arm of parasphenoid and the Isonidae, a new family group name PB, pharyngobranchial tooth plate for the genera Iso and Notocheirus, see below), PCL, postcleithrum "phallostethoid" (= Phallostethiformes or PFR, prefrontal Phallostethoidei, and including the Neo- PGQU, pterygoquadrate cartilage stethidae and Phallostethidae), "mugiloid" PLS, pleurosphenoid 1964 ROSEN: HALFBEAKS, KILLIFISHES, SILVERSIDES 221 PMX, premaxilla astic council, and patient criticism through- POP, preoperculum out the progress of the study. PRO, pro-otic For their many comments and recommend- PT, pterotic ations on special aspects of the work I thank PTT, posttemporal PV, prevomer Drs. James W. Atz, Reeve M. Bailey, QU, quadrate James Bohlke, Charles M. Breder, Jr., Don- SB, sesamoid bone ald P. de Sylva, Mr. Neal Foster, Drs. War- SC, scapula ren C. Freihoffer, P. H. Greenwood, Carl L. SCL, supracleithrum Hubbs, Clark Hubbs, Colin Patterson, SOC, supraoccipital C. Richard Robins, Bobb Schaeffer, C. La- SOP, suboperculum vett Smith, and William N. Tavolga. Drs. SPAL, sesamoid bone capping autopalatine Breder and Smith kindly read and criticized SPH, sphenotic the typescript. Dr. Klaus D. Kallman and SYM, symplectic Mr. R. Elwood Logan provided photographic UTE, underlying triangle of endochondral bone aid; Miss Mary Grace Dromi, technical as- sistance; and Dr. Reeve M. Bailey, Mrs. ACKNOWLEDGMENTS Lillian Dempster, Mr. William I. Follett, and The present work