From Kunlun Pass Basin, Northeastern Tibetan Plateau and Their Bearings on Development of Water System and Uplift of the Area

SCIENCE CHINA Earth Sciences • RESEARCH PAPER • April 2010 Vol.53 No.4: 485–500 doi: 10.1007/s11430-010-0048-5 Pliocene cyprinids (Cypriniformes, Teleostei) from Kunlun Pass Basin, northeastern Tibetan Plateau and their bearings on development of water system and uplift of the area WANG Ning & CHANG Mee-mann* Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China Received November 23, 2009; accepted February 25, 2010 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 Plio- cene 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. Gymnocypris, Schizothoracini, Pliocene, Kunlun Pass Basin of northeastern Tibetan Plateau, development of water system, uplift of the area Citation: Wang N, Chang M M. Pliocene cyprinids (Cypriniformes, Teleostei) from Kunlun Pass Basin, northeastern Tibetan Plateau and their bearings on development of water system and uplift of the area. Sci China Earth Sci, 2010, 53: 485–500, doi: 10.1007/s11430-010-0048-5 The Kunlun Mountain stretches along the southern border the area that is closely linked to the uplift of the Tibetan of Qaidam Basin, northeastern Tibetan Plateau, whereas Plateau and the global climate and environmental changes Kunlun Pass Basin is situated on the south slope of the mid- [5, 6]. The geology of this area has long attracted the atten- dle section of the East Kunlun Mountain (Figure 1). It is a tion of geologists and paleontologists worldwide. Paleon- fault basin, formed at the beginning of the late Cenozoic [2, tological studies conducted in this area, however, have fo- 3]. It contains comparatively thick late Cenozoic sediments cused mainly on palynology, ostracods, and mollusks, indi- (~700 m [4]), which documented the geological history of cating significant environmental changes since the Pliocene [7-10]. Vertebrate fossils from the Basin have not yet been specifically reported. *Corresponding author (email: [email protected]) There was only one fossil fish locality known in Tibetan © Science China Press and Springer-Verlag Berlin Heidelberg 2010 earth.scichina.com www.springerlink.com 486 WANG Ning, et al. Sci China Earth Sci April (2010) Vol.53 No.4 Figure 1 Geological map of East Kunlun Mountain and surrounding area, northeastern Tibetan Plateau (Based on Geological Map of Qinghai Province [1]). Plateau (Lunbola Basin [11]) before the team from the are extremely rare (Figure 2). Described so far from this Natural History Museum of Los Angeles County (LAM) area were Plesioschizothorax macrocephalus [11], a fossil and Institute of Vertebrate Paleontology and Paleoanthro- genus and species originally referred to the family Cyprini- pology (IVPP), led by Wang Xiaoming, started to work in dae; Hsianwenia wui [14], another fossil genus and species Qaidam Basin, northeastern Tibetan Plateau, at the end of referred to the subfamily Schizothoracinae (=Oreininae, last Century. Several vertebrate fossil localities, including Cyprinidae); and several disarticulated pharyngeal bones fish remains, were found in Qaidam Basin [12–14] (Figure with teeth referred to the Barbinae [13] of the Cyprinidae. 2). During the field seasons of 2006 and 2007, the team Both Plesioschizothorax macrocephalus and Hsianwenia worked in the Kunlun Pass Basin and discovered numerous wui were considered as belonging to the subfamily disarticulated fish bones and teeth as well as some mam- Schizothoracinae by Chang et al. [14]. mals [17]. The fish fossils were collected from the locality The Cyprinidae is the largest family of freshwater fishes. KL0607 (35°38′09.0″N, 94°05′05.6″E), about two kilome- Although works abound as to the phylogeny of the group ters east of the Qingzang Railway and 116 km southwest to during the last two decades, both from morphological and Golmud City, Qinghai Province (Figure 1). The altitude of molecular aspects [18-27], views are equally abundant the locality is 4769 m above the sea level (asl). This is one among ichthyologists on recognition of the subgroups of the of the few localities uncovered recently from the Plateau family, their scope, and their interrelationships. For pos- with a large quantity of fossil fish, and it is one of the high- sessing the unique “anal scales”, schizothoracins are re- est vertebrate fossil localities in the world. The fish remains garded as a monophyletic subfamily (Schizothoracinae) [16, from the Kunlun Pass Basin were collected from the Lower 28-32] or a subgroup (Schizothoracini) within the subfam- Member of the Qiangtang Formation [6]. The age of the ily Cyprininae [19, 33]. For their restricted distribution, Lower Member of the Qiangtang Formation is 2.58-1.77 schizothoracins usually were not included or only one spe- Ma based on a magnetostratigraphic study, ranges from the cies was included in a number of phylogenetic analyses of late Pliocene to early Pleistocene according to Song et al. the Cyprinidae or Cypriniformes [20-22, 24-27]. Because [6], or late Pliocene according to Wang et al.’s work on of lack of specimens, the group was rarely discussed in fossil mammals [17]. In this paper we adopt the view in the these works. Wherever more specimens of this group were latter work. The fish-bearing deposits are fluvial-lacustrine involved, the group was frequently treated as monophyletic dark gray mudstones intercalated with yellow brown muddy [18, 19, 31, 32, 33-37], regardless of which taxonomic rank sandstones or siltstones. (subfamily, lineage or tribe) the group is placed at. In a few The Cenozoic fossil fishes found from Tibetan Plateau recent works dealing with the phylogeny of the Cyprinidae, WANG Ning, et al. Sci China Earth Sci April (2010) Vol.53 No.4 487 Figure 2 Map of Cenozoic fossil fish localities and distribution of Recent Gymnocypris species in Tibetan Plateau, based on Wu and Wu [15] and Chen and Cao [16]. however, schizothoracins were considered non-monophy- tion and environment. We were able to identify some of the letic [38-41]. bones as belonging to Gymnocypris sp. indet., and a few In most morphological and molecular studies of the Cy- others to the lineage Schizothoracini gen. and sp. indet. priniformes and Cyprinidae, the subfamily Cyprininae [19, (subfamily Cyprininae). For the rest of bones, we could 20, 26, 27] or Series Barbini [18] is well supported, and the only refer them to the family Cyprinidae gen. and sp. indet. Schizothoracini, where included, is treated as one of its without any specifications. subgroups [19, 33]. In this paper, we follow Howes [19] and The zoogeography of the living schizothoracins has been Kullander et al. [33] to refer the materials, which we are studied and the evolutionary process of the group deduced able to identify as belonging to Gymnocypris, to the [30, 42]. The living schizothoracins were considered to have Schizothoracini lineage (=Tribe Oreinini [33], Schizotho- developed in correlation with the uplift of the Tibetan Pla- racinae [28]), subfamily Cyprininae. As for the lineage teau and were divided into three grades: primitive, special- (Tribe) name, we prefer Schizothoracini to Oreinini at pre- ized, and highly specialized. The division of the three sent, pending further works to clarify the priority of the ge- grades was based on the extent of modifications of their nus name, Schizothorax or Oreinus [33]. The lineage scales, barbells, and rows of pharyngeal teeth, and their dis- Schizothoracini is a comparatively large group with nu- tribution at three successive altitudes at which water tem- merous morphologically similar genera and species. The perature and precipitation decrease, and solar radiation and phylogenetic relationship of the group is in need of further evaporation increase [30]. The genus Gymnocypris from our work. materials falls in the highly specialized grade. From the numerous fish bones collected from the locality KL0607, Kunlun Pass Basin, we could recognize fishes belonging to two cypriniform families, the Cyprinidae and 1 Materials and methods Nemacheilidae. In this paper, we describe the cyprinid bones and discuss some problems concerning their distribu- All fish remains from Kunlun Pass Basin consist of disar- 488 WANG Ning, et al. Sci China Earth Sci April (2010) Vol.53 No.4 ticulated, incomplete bones. They do not seem buried in situ 2 Systematic paleontology but sorted and transported by water, then re-deposited, for only relatively thick bones or thick parts of bones are pre- Superorder Ostariophysi Sagemehl, 1885 served.

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