Scientists from Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences found and described fossil nemacheilids from the Pliocene Lower Member of Qiangtang Formation in the Kunlun Pass Basin, northeastern Tibetan Plateau, at a locality 4769 m above the sea level. The materials consist of numerous disarticulated and incomplete bones. This is the first fossil record of this group on the Tibetan Plateau as well as in China, researchers reported in the latest issue of Scince China Earth Sciences, 2012, 55 (5).
Situated on the south slope of the East Kunlun Mountain, northeastern Tibetan Plateau, the Kunlun Pass Basin is a fault basin formed at the beginning of the late Cenozoic. It contains comparatively thick late Cenozoic sediments (~700 m), which documented the geological history of the area that is closely linked to the uplift of the Tibetan Plateau and the global climate and environmental changes.
Researchers assigned the fish remains to the Nemacheilidae based on the fused compound centrum of the 2nd and 3rd vertebrae with developed bifurcate lateral processes of the 2nd vertebra. The fossils also include the maxilla, the dentary, the anguloarticular, the quadrate, the hyomandibular, the opercle, the basihyal, the urohyal, the anterior ceratohyal, the posterior ceratohyal, the interhyal and the supracleithrum. These bones are very similar to their counterparts in some species of a recent nemacheilid genus, Triplophysa (Nemacheilidae, Cypriniformes), which is widely distributed on the Tibetan Plateau.
The nemacheilid fossils are much more abundant than the remains of schizothoracines embedded in the same horizon at the same locality. This would imply that the number of individuals of Triplophysa was much higher than that of schizothoracines when they were alive in the area. This, in turn, indicates that the environment was, on the whole, more favorable for Triplophysa than for schizothoracines to survive. In Recent ichthyofauna of the Tibetan Plateau, Triplophysa prevails over schizothoracines in the number of individuals in the high elevations and small water bodies.
“Based on the fossil dominance of Triplophysa over schizothoracines and their taphonomical conditions, it appears that the water system at the Kunlun Pass area during the Pliocene might not be extensive lakes or large rivers with broad valleys”, said lead author WANG Ning of the IVPP, “There might have been a few mountainous, relatively torrential rivers with many small, shallow streams connecting the water systems from the north and south of the East Kunlun Mountain. The environment of the Kunlun Pass Basin area during the Pliocene must be very harsh, and the altitude of the area might already have been higher than we previously suggested. The uplift of the area must be less than 1000 m since the Pliocene”.
This study was supported by the Knowledge Innovation Program of Chinese Academy of Sciences, National Basic Research Program of China, National Natural Science Foundation of China and Key Laboratory of Evolutionary Systematics of Vertebrates, IVPP, CAS.
Fig. 1 Compound centrum of the 2nd and 3rd vertebrae of fossil nemacheilid (a-d) and the same vertebrae with bony capsule of swim bladder in Recent nemacheilid Triplophysa pseudoscleroptera (e,f). a, e dorsal view; b, f ventral view; c anterior view; d posterior view. Scale bars: 0.5 mm for (a)–(d), 1 mm for (e) and (f). (Image by WANG Ning)
