Phyletics and biogeography of the aspinine cyprinid fishes Gordon Howes Department of Zoology, British Museum (Natural History), Cromwell Road, London SW7 5BD Introduction This study was initiated by the examination of specimens of the Hwang-Ho dace, Leuciscus mongolicus (Kessler, 1876) in the collections of the American Museum of Natural History. Even a cursory examination cast doubt on their assignment to the genus Leuciscus, and a more detailed anatomical study, reported herein, indicates that the species should be allocated to a new genus. Study of this material has also led to a reappraisal of the genus Leuciscus and to a discussion of the phyletics and zoogeography of the aspinine cyprinids. Methods and materials As in previous studies (Howes, 1978, 1980, 1981) a wide range of both barrelled and non-barbelled Old World cyprinids have been examined. The materials listed in those papers have been re-examined together with more recently prepared material. In addition, skeletal preparations of many Nearctic taxa have also been studied. The following species were dissected, or skeletal preparations examined. Abramis brama\ Algansea tincella; Aspiolucius esocinus; Aspiopsis merzbacheri; Aspius aspius; Aspius vorax; Chondrostoma nasus; Elopichthys bambusa; Gila bicolor; G. copei; G. crassicauda; G. cypha; G. elegans; G. nigrescens; G. pandora; G. robusta (these include Michigan Museum specimens); Lavi-nia exilicauda; Leuciscus borysthenicus; L. cephalus; L. idus; L. fellowesii; L. lehmanni; L. leuciscus; L. orientalise L. schmidtii; L. smyrnaeus; L. souffia; L. svallizae; L. waleckii (including the syntypes of L. waleckii sinensis in the Swedish Museum of Natural History); Luciobrama macrocephalus; Mylo-cheilus caurinus; Ochetobius elongatus; Oreoleuciscus humilis; O. pewzowi; O. potanini\ Orthodon microlepidotus; Pelecus cultratus; Pogonichthys macrolepidotus; Ptychocheilus lucius; P. grandis; P. oregonensis\ Rhynchocypris variegatus; Tinea tinea; Tribolodon brandti; T. jouyi; Xenocypris argenteus. The concept of Leaciscus and the status of Leuciscus mongolicus (Kessler) The daces and chubs of the genus Leuciscus Cuvier, 1817 form the most speciose group of Palearctic cyprinid fishes, there being at least 36 nominal species (the number listed in the BMNH catalogues). The majority of Leuciscus species are alike in having moderately deep and stout bodies, broad cranial bones (including the ethmoid and supraorbital), a ventrally directed basioccipital process with a well-formed masticatory plate, biserially arranged uncinate pharyngeal teeth, and a short-based anal fin. Comparative studies (Howes, 1978, 1980, 1981) suggest that these 'diagnostic' characters are plesiomorphic for non-barbelled cyprinids. Leuciscus, as presently recognized, cannot be defined by a set of unique characters and is therefore a non-monophyletic assemblage. One species of 'Leuciscus', L. mongolicus (Kessler, 1876), has, however, a suite of derived characters that sets it apart from the corpus of Leuciscus species (detailed in Table I). Some of these specializations are shared with genera of the aspinine group sensu Howes, 1978 (see pp. 29 1 below) and are as follows: Bull. Br. Mus. nat. Hist. (Zool.) 47(5): 283-303 Issued 25 October 1984
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