Andean killifish Orestias

p. 110-214 : ill., maps ; 26 cm.Includes bibliographical references (p. 211-214)."The ichthyofauna of the high Andes is assumed to be of low taxonomic diversity. Only three fish genera, the killifish Orestias and the catfishes Astroblepus and Trichomycterus include species endemic to the Altiplano, the high-attitude plateau between the eastern and western slopes of the central Andes. The atherinid Basilichthys is known doubtfully from the Altiplano. In the last revision of the genus Orestias, Tchernavin (1944a) recognized 20 species and five subspecies. This small number was taken as evidence of the low diversity of fish of the Titicaca Basin. However, in the past two years, five new Orestias species have been described, three from Lago Titicaca (Lauzanne, 1981) and two from the Altiplano of northern Chile (Arratia, 1982). With the benefit of large recent collections, 43 species of Orestias are recognized in the present revision, 14 being described as new (O. gracilis, O. rotundipinnis, O. farfani, O. gymnotus, O. hardini, O. ctenolepis, O. ascotanensis, O. richersoni, O. multiporis, O. mundus, O. ututo, O. imarpe, O. tomcooni, and O. robustus). Seven synapomorphies described here define Orestias as a monophyletic group: (1) pelvic fins and fin girdle are absent; (2) vomer is absent; (3) middle anal and middle dorsal fin radials are cartilaginous, rather than ossified; (4) bony anterior and posterior ceratohyal are separated ventrally by a large gap filled with cartilage; (5) first postcleithrum is absent; (6) anguloarticular lacks a ventral extension parallel to the retroarticular; and (7) there is a unique squamation and head pore pattern characterized by a prominent lyre-shaped arrangement of minute neuromasts and a prominent median dorsal ridge of scales running from the top of the head to the dorsal fin origin. Primary characters used to distinguish Orestias species are overall body shape and squamation pattern. Diversity of form is marked. There are large, troutlike midwater predators, such as O. cuvieri, diminutive inshore species such as O. minutus and O. minimus, and very wide-headed and wide-bodied species, with large, thick granulated scales, such as O. luteus and O. albus. The diversity among Orestias species in Lago Titicaca, the large, high-altitude lake of the Altiplano of Peru and Bolivia, has led to the application of the term 'species flock' to this group of lacustrine killifish. However, the Orestias of Titicaca do not form a monophyletic group, and it is recommended that the term 'species flock' not be used for the killifishes limited to the lake. The known range of Orestias extends from northern Peru to northern Chile. It is expected that the number will rise with additional collecting, because collections are lacking from many of the small, isolated lakes of the Altiplano; also, single specimens of apparently new species are known, yet remain undescribed. The hypothesis of a close relationship between Orestias and the Anatolian cyprinodonts is reviewed"--P. 110