Pliocene cyprinids (Cypriniformes, Teleostei) from Kunlun Pass Basin, northeastern Tibetan Plateau and their bearings on development of water system and uplift of the area

Here described are the cyprinid fossils from the Pliocene Lower Member of Qiangtang Formation of the Kunlun Pass Basin, northeastern Tibetan Plateau, collected at a locality 4769 m above the sea level (asl). The materials consist of numerous disarticulated and incomplete bones as well as thousands of pharyngeal teeth, fin rays, and vertebrae. The fossils were referred to the genus Gymnocypris, lineage Schizothoracini, family Cyprinidae; the lineage Schizothoracini; and the family Cyprinidae respectively. The Schizothoracini is a freshwater fish group endemic to the Tibetan Plateau and its surrounding area. Previous workers on living schizothoracins regarded that Gymnocypris belongs to the highly specialized grade of the group, colonizing higher altitudes than other members of the group. Two species are so far unequivocally assigned to the genus, i.e., G. przewalskii and G. eckloni, and they are inhabiting Qinghai Lake and the waters on both north (the Golmud River) and south (upper reach of the Yellow River) sides of the East Kunlun Mountain, respectively. The abundant fossil schizothoracins occur in the Kunlun Pass Basin on the southern slope of the East Kunlun Mountain (at 4769 m asl), close to the present Golmud River, indicating comparatively rich waters in the area and possible connections between the water systems on north and south sides of the East Kunlun Mountain during the Pliocene. This also suggests a more humid climate in the area during the Pliocene than it is today. The presence of the highly specialized schizothoracin Gymnocypris may also imply less amplitude of uplift (approximately 1000 m) in the area since the Pliocene than previously proposed.