Journal of Fish Biology (1998) 52, 937–950 Leuciscus torgalensis and L. aradensis, two new cyprinids for Portuguese fresh waters M. M. C†, N. G. B*, J. A. R  M. J. C-P Departamento de Zoologia, Faculdade de Cie ˆncias, Bloco C2, 3 0 Piso, Campo Grande, 1700 Lisboa, Portugal and *Zoological Institute of Russian Academy of Sciences, St Petersburg, 199034 Russia (Received 14 October 1997, Accepted 4 January 1998) The description of two new Portuguese freshwater fish species is presented. Leuciscus torgalensis occurs in the Mira basin and Leuciscus aradensis in the Arade basin and in two other small southern basins. The type material is deposited in the collections of the Museu Bocage, Lisbon (MB). The general external similarity between L. torgalensis and L. aradensis and two further species, L. carolitertii and L. pyrenaicus is high. The main external diagnostic character for both new taxa is the lower number of scales of the lateral line, despite the slight differences between them. Head form is a distinctive character between the two new species; such that head width is greater in L. aradensis. Distinct osteological characters between both L. torgalensis and L. aradensis and the other Iberian Leuciscus species are: the supraorbital canal and the modal vertebral formula that are shorter and lower in the new species, respectively. The preopercular–mandibular canal communication exists in L. aradensis, but not in L. torgalensis. Allozyme and mitochondrial DNA data also supported a monophyletic clade of Mira and Arade and the distinction of the two new species. The differentiation of the new species occurred either by an early isolation of the Mira and the Arade basins or by ecological conditions after the disjunction of all basins in Portugal, during the early Quaternary.  1998 The Fisheries Society of the British Isles Key words: Iberian cyprinids; new species; Leuciscus torgalensis; Leuciscus aradensis; morphology; osteology. INTRODUCTION Cyprinid fish of the genus Leuciscus Cuvier, 1816, which includes about 35 species, are distributed widely throughout Eurasia from the Iberian Peninsula to the Amur River and from the Kolyma River to the Tigris–Euphrates basin (Bogutskaya, 1995). In the Iberian Peninsula, the taxonomy of the genus Leuciscus has been controversial due to the slight differences assumed for meristic and morphometric characters between the two described endemics—L. carolitertii Doadrio, 1988 and L. pyrenaicus Gu ¨ nther, 1868 (Doadrio et al., 1991). The distribution area of the former species ranges from the rivers of Galicia to the Mondego basin (northern populations), while L. pyrenaicus has been considered to occupy all the southern half of the Iberian Peninsula from the small basins south of Mondego in Portugal to the Mijares basin in Spain (southern populations) (Costa Pereira, 1995). †Author to whom correspondence should be addressed. Tel.: (351) 1 7573141; fax: (351) 1 7597716; email: mmcoelho@fc.ul.pt 937 0022–1112/98/050937+14 $25.00/0/jb980642  1998 The Fisheries Society of the British Isles