The Late Miocene‘ovibovin’bovids in Eurasia

During the Late Miocene,numerous medium to large-sized herbivores,that resemble the living Ovibos in skeletal morphology,dispersed throughout the Holarctic realm and comprised eleven genera:Lantiantragus,Shaanxispira,Tsaidamotherium,Criotherium,Mesembriacerus,Hezhengia,Urmiatherium,Parurmiatherium,Plesiaddax,Sinotragus,and Prosinotragus.These genera are primarily found in eastern Asia,in which nine genera are found in northern China,as well as in countries in eastern Europe and western Asia.They are distinguished by unique characteristics,including a perpendicular braincase,specialized horn cores,and a robust basioccipital.Previous studies have often classified these‘ovibovin’bovids as part of the conventional subfamily/tribe Ovibovinae/Ovibovini,along with extant Ovibos.Nevertheless,an increasing number of studies do not support the monophyly of the subfamily/tribe Ovibovinae/Ovibovini,nor is a close relationship likely between these Late Miocene‘ovibovin’bovids and extant Ovibos.Among the eleven genera of‘ovibovin’bovids,Plesiaddax,Hezhengia,and Urmiatherium are often considered to have a very close relationship and conventionally form the tribe Urmiatheriini.However,previous phylogenetic analyses do not support the monophyly of Urmiatheriini.This paper presents a summary of the transmutation of the terms Ovibovidae/Ovibovinae/Ovibovini/Ovibovina,the temporal and spatial distribution of the Late Miocene‘ovibovin’bovids in Eurasia,the principal characteristics of these taxa,and the previous phylogenetic analyses.

Late Miocene Woods of Taxodiaceae from Yunnan, China

Late Miocene woods were investigated from the Luhe Basin in Chuxiong Borough, central Yunnan, China. The calcified woods preserved in the Shigucun member of the Shihuiba Formation, are represented by fallen logs and stumps. Two species of fossil wood, Taxodioxylon cryptomeripsoides Schonfeld 1953 and T. cunninghamioides Watari 1948, are described. Their anatomical structure shows striking similarities to the woods of Cryptomeria and Cunninghamia respectively. That the two fossil woods are classed in the Taxodiaceae suggest a subtropical, humid, and warm environment in Lithe during Late Miocene. They compare favorably to other fossil specimens and species reported from localities ranging from Cretaceous to Pliocene. This is the first record of the presence of the species T. cryptomeripsoides and T. cunninghamioides in late Miocene of Yunnan.

Bamboo Leaf and Pollen Fossils from the Late Miocene of Eastern Zhejiang,China and their Phytogeological Significance

Fossil bamboo leaves and pollen from Upper Miocene deposits of the Shengxian Formation in Tiantai and Ninghai counties, eastern Zhejiang, China represent a rare record in Asia. The distinctive pseudopetiole and parallel venation of the leaf blades and the clearly thickened annulus of the pollen aperture place them in the subfamily Bambusoideae. Morphological analysis supports the determination of these fossil leaves as belonging to the genus Bambusium and two new species are described. Bambusium latipseudopetiolus Q.J. Wang et B.N. Sun sp. nov. has a distinctly wide pseudopetiole of 0.23 cm in width and 0.40 cm in length, several vascular bundles on parallel veins, and 5-8 lateral veins on both sides of the midrib. Bambusium longipseudopetiolus Q.J. Wang et B.N. Sun sp. nov. has a distinctly long pseudopetiole of 0.60 cm in length and 0.10 cm in width, several vascular bundles on the pseudopetiole, and 6 lateral veins on both sides of the midrib. Pollen grains from the same layer provide additional evidence of bamboos. They are characterized by 32.0-51.0 μm in diameter, a round pore 3.0-4.0 μm in diameter with a broad thickened annulus 2.5-3.5 μm around, and several conspicuous secondary folds on the exine surface. The morphological analysis leads to their assignment to Graminidites bambusoides Stuchlik. These fossils are important for the study of bamboo phytogeography in China. They demonstrate that there were bamboos growing in southeastern China during the Late Miocene and that bamboos in Zhejiang begin to diversify no later than the Late Miocene. In combination with bamboo fossils from other places, it seems that bamboos had a wide distribution across southern China during the Miocene, ranging from southwestern Yun＇nan to southeastern Zhejiang.

A New Species of Tsuga(Pinaceae) based on Lignified Wood from the Late Miocene of Central Yunnan, China, and Its Paleoenvironmental Implications

A new species, Tsuga nanfengensis sp.nov.（Pinaceae）, is described on the basis of lignified fossil wood from the late Miocene of the Xianfeng Basin, central Yunnan, southwestern China.Detailed observation of the fossil wood specimens show the following characteristics： distinct growth rings, absence of resin canals, uniseriate bordered pits in the radial wall of tracheids, ray tracheids and piceoid and cupressoid cross-field pits.These features indicate similarities to the wood of extant Tsuga canadensis, T.chinensis, and T.dumosa.According to the fossil record, Tsuga was present in Xundian County during the Miocene.Today Tsuga is drought intolerant, preferring wet conditions with no extant species growing naturally in Xundian County.The presence of Tsuga in the Miocene of Xundian County indicates a humid climate consistent with previous palaeoclimatic reconstructions showing a wetter and probably shorter dry season in the Miocene, relative to the present day.Therefore, the change in the local climate such as increasing aridity through the Miocene might explain the local extinction of Tsuga from central Yunnan.

Structure,Timing,and Mechanism of the Pliocene and Late Miocene Uplift Process of the Ailao Shan-Diancang Shan,SE Tibet,China

The uplift of the Ailao Shan-Diancang Shan （ASDS） along the Ailao Shan-Red River （ASRR） shear zone is an important geological event in the southeastern margin of Qinghai-Tibet Plateau tectonic domain in the Late Cenozoic, and it preserves important information on the structures, exhumationai history and tectonic evolution of the ASRR shear zone. The uplift structural mode and uplift timing of the ASDS is currently an important scientific topic for understanding the ASDS formation and late stage movements and evolution of the ASRR shear zone. The formation of the ASDS has been widely considered to be the consequence of the strike-slip movements of the ASRR shear zone. However, the shaping of geomorphic units is generally direct results of the latest tectonic activities. In this study, we investigated the timing and uplift structural mechanism of the ASDS and provided the following lines of supportive evidence. Firstly, the primary tectonic foliation of the ASDS shows significant characteristic variations, with steeply dipping tectonic foliation developed on the east side of the ASDS and the relatively horizontal foliation on the west side. Secondly, from northeast to southwest direction, the deformation and metamorphism gradually weakened and this zone can be further divided into three different metamorphic degree belts. Thirdly, the contact relationship between the ASDS and the Chuxiong basin-Erhai lake is a normal fault contact which can be found on the east side of the ASDS. 40^Ar/^39 Argeochronology suggests that the Diancang Shan had experienced a fast cooling event during 3-4 Ma. The apatite fission track testing method gives the age of 6.6-10.7 Ma in the Diancang Shan and 4.6-8.4 Ma in the Ailao Shan, respectively. Therefore the uplift of the ASDS can be explained by tilted block mode in which the east side was uplifted much higher than the west side, and it is not main reason of the shearing movements of the ASRR shear zone. The most recent uplift stages of the ASDS happened in the Pliocene （3-4 Ma） and Late Miocene （6-10 Ma）.

Morphology and taxonomy of Gazella （Bovidae, Artiodactyla） from the Late Miocene Bahe Formation, Lantian, Shaanxi Province, China

Gazella羚羊是"三趾马动物群"中常见成员,在晚中新世至更新世地层中广泛分布,演化速率相对较快,具有重要的生物地层学及生态指示意义,但在我国尚未有保德期之前的化石报道。本文研究的化石发现于陕西蓝田灞河组中部,磁性地层学资料显示其年代为晚中新世灞河期。化石标本包括了5个近乎完整的头骨、下颌以及颅后骨骼。根据发现的标本装架起第一个完整的Gazella羚羊骨架。形态对比与测量数据表明,蓝田标本与巴基斯坦西瓦里克发现的Gazella lydekkeri非常相近,而不同于欧洲晚中新世常见的Gazella各种以及我国发现的种类。从肢骨的形态分析与测量比例数据来看,Gazella cf.G.lydekkeri适合快速奔跑运动,可能生活在相对开阔的环境中,与灞河期动物群的生态类型以及与灞河组沉积学、同位素地球化学等研究所指示的相对干旱、半干旱的开阔草原环境相一致。

Late Miocene Pods and Leaves of Albizzia (Leguminosae:Mimosoideae) from Yunnan,SW China and Their Phytogeographic Implications

Albizzia is a leguminous genus belonging to the subfamily Mimosoideae with approximately 150 modern species, widely distributed in the tropical and subtropical regions of Asia, Africa, Australia and America. Among them, 17 species are mainly distributed in southern and southwestern China. Abundant fossils of the subfamily Mimosoideae, including leaves, pods, flowers and wood, have been reported from the Cretaceous and Paleogene strata of the Northern Hemisphere. However, Neogene records of Mimosoideae are relatively scarce. In this study, fossil pods and leaves belonging to the genus Aibizzia from the Bangmai Formation of Yunnan, China were described. They were assigned to three species, including Albizzia scalpeUiformis Guo, Li and Xie Emended, Albizzia cf. kalkora （Roxb.） Prain and Albizzia sp. The occurrence of Albizzia fossils from Lincang not only gives important information on the Neogene plant diversity from Yunnan--a worldwide famous biological hotspot--but also provides additional evidence for its phytogeographic history.

Magnetochronology of Late Miocene Mammal Fauna in Xining Basin,NE Tibetan Plateau, China

The Xining basin is located in the northeastern margin of the Qinghai-Tibet Plateau. It is a rift basin formed in Mesozoic and Cenozoic and structurally belongs to the intersection of Kunlun and Qilian Mountains. Cenozoic fluvial and lacustrine sedimentary strata are continuous in the Xining basin, with a thickness of more than 800 m, completely recording the deformation uplifting, weathering and denudation history and climate change process of the northeastern plateau. Currently, early Miocene Xijia fauna, early Middle Miocene Danshuilu fauna and late Middle Miocene Diaogou fauna are discovered in the Xining basin, which provide an important basis for the stratigraphic correlation of the Cenozoic strata in the Xining basin. However, in the next few decades, there are no reports about the large mammal fossils in the Xining basin, especially about late Miocene fauna. The author discovered a large amount of mammal fossils in the Neogene sedimentary strata in Huzhu area, Xining basin. According to the identification results of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, these fossils mainly included Hipparion dongxiangense, Chilotherium sp., Parelasmotherium sp., Stephanocemas sp. and Kubanochoerus sp. and their age was early Late Miocene. Since the discovery of this set of fossils directly filled the blank that there were no large mammal fossils in the Xining basin in Late Miocene, it was very important for studying the magnetic stratigraphic chronology of fossil-forming strata and establishing the paleomagnetic chronology scale plate of mammal fossils. In this paper, the paleomagnetic data of the fossil-forming stratigraphic profile, Banyan profile, were measured and the paleomagnetic records were collected through high density sampling, and finally the paleomagnetic polarity column of the profile was established. The results showed that five positive and five negative polarity segments were recorded in Banyan profile, which corresponded well to the polarity between C3 Br.1 n-C4 n.2 n in the standard polarity column. The age of profile top was about 7.25 Ma and profile bottom was about 8.4 Ma, with an age range of 1.15 Ma. The mammal fossils discovered this time were exposed between positive and negative polarities N5 and R5 at the bottom of the profile, corresponding to C4 r.1 r at negative polarity and C4 n.2 n at positive polarity in the standard polarity column. The age of mammal fossils was about 8.3 Ma. The paleomagnetic chronology of the strata and paleontological fossils determined the absolute age of late Miocene mammal fossils and expanded the upper age of late Miocene Xianshuihe Formation(N1 xn) in the Xining basin, which had provided new basic data for further studying the stratigraphic deposition and correlation of late Cenozoic strata and regional environmental evolution.

First Report of Late Miocene Mammals Including Chilotherium in the Xining Basin,NE Tibetan Plateau,China

Objective Xining basin is located in the northeastern Qinghai- Tibetan Plateau, which tectonic location belongs to a junction of the Kunlun and Qilian mountains. The southern, northern and western parts of the basin are restricted by the Laji, Daban and Riyue mountains fault zones, and go eastward into the Longzhong basin in Gansu Province. A succession of Cenozoic lacustrine sedimentary strata has been well developed in the Xining basin, with sediments over 800 m thick.

Late Miocene Environmental Crises and Their Impacts:Desiccation of the Mediterranean and Its bearing on World Desertification and Hominid Appearance

The ancient Mediterranean was once dried up around6~5.3million years ago.It is a landmark event,which had great impact on global environment and climate.However,few references are available in the literatures on this topic,

A new Late Miocene Hystrix(Hystricidae,Rodentia)from Turkey

TheÇorakyerler fossil locality in Anatolia reveals unique faunal elements.This study introduces Hystrix kayae sp.nov.,a new Late Miocene porcupine initially classified as Hystrix sp.Yavuz et al.,2018.This finding expands our knowledge of Late Miocene Anatolian porcupines,bringing the total number of known species to three.H.kayae sp.nov.is larger than Hystrix aryanensis and exhibits greater upper cheek tooth crown height.Its cheek tooth morphology differs from Hystrix depereti,and it possesses distinctive U-shaped choanae unlike Hystrix primigenia.TheÇorakyerler locality may predate sites with H.aryanensis and H.primigenia but aligns temporally with Hystrix parvae localities.This study enhances our understanding of Late Miocene porcupine diversity in Anatolia,emphasizing the importance ofÇorakyerler in unraveling the evolutionary history of these fascinating mammals.

Three-dimensional reconstruction of Late Miocene Trapa from eastern Zhejiang Province,China:Insights into its phytogeography and evolution

Abundant plant fossils were found in the Upper Miocene Shengxian Formation,eastern Zhejiang Province,China,among which Trapa belongs to a dominant population.The fossil fruits of Trapa were well preserved with abundant details.However,due to compaction during fossilization,Trapa fruits were often flattened,leading to the loss of some characteristic features.Thereby,a bias in taxonomic and phylogenetic studies would occur when such studies were based on these fruit fossils.In this study,we present the first quantitative three-dimensional reconstruction of compressed Trapa fruit fossils to restore their original morphology prior to burial.This approach provides a novel perspective for the identification and classification of compressed fruit fossils.The three-dimensional reconstruction of Trapa fruit fossils enabled accurate comparisons with extant species.We subsequently identified it as a new species,named Trapa radiatiformis L.Xiao sp.nov.,revealing differences from previously known taxa of Trapa.Importantly,our comparison suggests that the long lower horns and residual stalk may represent inherent characteristics of early Trapa fruits.However,these traits gradually degenerated during fruit evolution,resulting in morphological simplification during geological time.T.radiatiformis with primitive features exhibits good resemblance to Trapa natans fruit characteristics,which means it may be an ancestor of T.natans.We summarize the palaeogeographic distribution of fossil Trapa using previously published literature and demonstrate that the genus was mostprosperous in the Miocene and exhibited the same distribution as that at present.Additionally,through detailed morphological comparisons between Trapa and Hemitrapa fruits,along with phylogenetic analysis within the Primotrapa genus itself,we propose a homology between Trapa and Hemitrapa,suggesting that they could have a common ancestor.

西藏聂拉木亚汝雄拉晚中新世化石及其古环境意义

西藏聂拉木亚汝雄拉南坡保存有较厚的新生代达涕古湖盆沉积物,并产出晚中新世晚期福氏(垂鼻)三趾马(Hipparion(Cremohipparion)forstenae)化石,是研究青藏高原喜马拉雅地区新生代隆升与环境变迁的重要区域之一。目前对喜马拉雅山脉代表性新生代沉积盆地的地层与古脊椎动物化石的研究工作主要集中在札达和吉隆盆地,对达涕古湖盆的研究程度仍很低。2020年,由中国科学院古脊椎动物与古人类研究所组织的第二次青藏高原综合科学考察研究古生物分队,对聂拉木亚汝雄拉地区开展中-新生代地层与古生物调查,在新近纪地层中采集到一小批脊椎动物化石,包括鲤科咽齿、犀类、有蹄类和鼠兔类。其中,鼠兔类化石归属于艾氏拟美兔(Bellatonoides eroli),这是该属在青藏高原地区的首次发现,指示其产出层位的生物地层年代不会晚于晚中新世早期(灞河期)。根据哺乳动物化石,目前可从亚汝雄拉剖面中识别出两个不同的层位和年代,即上部湖滨相地层产福氏(垂鼻)三趾马,其年代为晚中新世晚期(保德期);下部湖相地层产艾氏拟美兔,其年代可能为晚中新世早期(灞河期)。此前艾氏拟美兔发现于土耳其安卡拉(Ankara)和我国内蒙古中部地区中中新世晚期-晚中新世早期的地层中,通常与灵长类及其他森林型哺乳动物共同出现;福氏(垂鼻)三趾马分布于西藏吉隆和山西保德晚中新世晚期地层中,被认为适应于开阔生境,海拔分布不超过2900m。化石证据显示聂拉木达涕古湖盆在晚中新世早期至晚期的古海拔可能比现代高度低了近2000m,古植被类型存在从晚中新世早期的森林到晚中新世晚期的森林草原环境的转变,整体上晚中新世亚汝雄拉的古环境远比现代要适宜得多。

青藏高原东南缘昭通盆地晚中新世到上新世古环境演化过程

青藏高原东南缘的云南区域是研究晚新生代以来气候和环境演化的重要区域之一。虽然针对云南区域已经开展了大量古气候和古环境演化的研究,但是晚中新世到上新世云南区域湿度变化的记录仅为碳同位素和孢粉记录,且分辨率较低。因此,该区域缺乏晚中新世到上新世连续的高分辨率古湿度变化记录。本研究主要基于云南省东北部昭通盆地内晚中新世到上新世的沉积物岩心,通过对沉积物粒度的测试分析,综合沉积序列、岩性特征和沉积构造,表明:昭通盆地在8.8~6.2 Ma以沼泽亚相沉积环境为主;在6.2~2.8 Ma以浅湖亚相沉积环境为主;在2.8~2.6 Ma以湖滨亚相沉积环境为主。昭通盆地沉积物粒度参数记录的晚中新世到上新世云南区域呈现干旱化的趋势。结合前期该钻孔黏土矿物和化学风化的相关成果,认为晚中新世到上新世南亚季风呈现逐渐减弱的趋势,并主要受控于全球变冷和全球CO_(2)浓度降低的影响。

Late Cenozoic uplift of the Liupan Mountains:Evidence from the Neogene loess deposits

The Liupan Mountains,one of the important mountain ranges in western China,are located on the boundary between the northeastern Tibetan Plateau and the Ordos Block.The uplift history of the Liupan Mountains remains controversial.Loess deposits are good tracers of regional tectonic and geomorphic changes,because loess is sensitive to erosion and the formation and preservation of loess requires relatively flat highlands and relatively stable tectonic environments.We investigated the distribution of Neogene loess deposits on the western piedmont of the Liupan Mountains and examined a near-continuous loess section(Nanping section)on the piedmont alluvial highlands.Correlation of magnetic susceptibility stratigraphy with the QA-ⅠMiocene loess sequence dates this 56-m section covering the interval from~8.1 to 6.2 Ma.The lower boundary age of this section,together with previously reported Zhuanglang red clay(sand-gravel layers with intercalated loess during~9–8 Ma and near-continuous loess during~8–4.8 Ma)and Chaona red clay(~8.1–2.58 Ma),indicates that the Liupan Mountains were uplifted in the late Miocene(~9–8 Ma)and basically formed by~8 Ma,attesting to no intense mountain building since that time.In addition,based on the information from the Zhuanglang core and the QA-Ⅰsection,we infer that sizable parts of the Liupan Mountains were uplifted during the late Oligocene–early Miocene and did not experience intense uplift during~22–9 Ma.

印度Haritalyangar地区晚中新世猪类化石新材料

描述了印度北部比拉斯布尔区喜马偕尔邦Haritalyangar地区中西瓦利克的猪类化石上、下颌及牙齿材料。Haritalyangar地区以晚中新世动物群、古人类和其他灵长类动物的多样性而闻名。研究材料为作者之一(ARS)在该地区多次野外季采集的猪类化石;猪类化石地点和最近报道的长鼻类化石地点(含古猿化石地点)均被绘制在地图上。这些化石地点广泛分布于Makkan Khad到Sir Khad区域内的“Lower Alternations”层和“Upper Alternations”层。猪类化石被鉴定为3个属:原河猪属Propotamochoerus(P.hysudricus)、河马齿河猪属Hippopotamodon(H.sivalense)和云南猪属Yunnanochoerus(Y.dangari)。Propotamochoerus hysudricus为中西瓦利克最常见的化石猪类,新发现的Yunnanochoerus dangari进一步证明这种古猪类化石仅在Haritalyangar地区有少量遗存。Haritalyangar地区新发现的猪类化石组成与巴基斯坦的Nagri动物群相近。基于猪类化石进行的Potwar高原年代地层学对比表明,Haritalyangar地区的“Lower Alternations”层的年龄范围为~10–9 Ma,与最新的磁极性地层学年代范围很接近。

太行山东麓井陉首次发现三趾马动物群

在太行山东麓井陉县首次发现了三趾马动物群,该动物群至少包括食肉目(猫科Felidae gen.et sp.indet.和鬣狗科Hyaenidae gen.et sp.indet.)、奇蹄目(林氏列角犀Dihoplus ringstroemi和平齿三趾马Sivalhippus platyodus)、偶蹄目(原河猪Propotamochoerus sp.、弓颌猪Chleuastochoerus sp.、山西兽Schansitherium sp.、古麟Palaeotragus sp.、羊羚Dorcadoryx sp.、高庄羚羊Gazella gaozhuangensis和似葛氏羚羊G.cf.gaudryi)等,显示其时代可与山西榆社盆地高庄组桃阳段相对比,为晚中新世晚期至上新世最早期,约6.0~5.2 Ma,大致对应于MN(欧洲哺乳动物分期)13后段。由于该化石地点覆于唐县期夷平面上,显示了该夷平面的隆升时段当不早于上新世。另一方面,动物群面貌指示了一个与现代迥异的开放的、温暖湿润的森林草原环境。

沙巴地区新生代碎屑岩物源分析及构造意义:锆石年代学和Lu-Hf同位素组成约束

沙巴地区位于印度‒澳大利亚、太平洋和菲律宾海板块交汇区,其发育的新生代沉积对理解婆罗洲北部的沉积‒构造演化具有重要意义。本文对沙巴北部始新世‒中新世碎屑岩开展岩石学、锆石U-Pb年代学及Lu-Hf同位素研究,结果表明:该套碎屑岩包括岩屑石英砂岩和长石岩屑石英砂岩,其中始新统Trusmadi组碎屑锆石年龄主要峰值为160 Ma和120 Ma,对应年龄群(185~145 Ma和140~100 Ma)的εHf(t)值分别为–15.6~+14.8和+0.6~+12.2,表明源区新生地壳物质贡献明显。始新统‒中新统Crocker组碎屑锆石年龄主要峰值为248 Ma,次要峰值为1860 Ma、438 Ma、280 Ma和120 Ma,主要年龄群(265~220 Ma)的εHf(t)值为–11.9~+9.9。中新统Kudat组的碎屑锆石年龄集中在120 Ma、εHf(t)值(+1.8~+9.0)均为正值,次要峰值174 Ma。本次研究认为Trusmadi组砂岩物源主要受控于越南大叻带和婆罗洲西部中生代花岗质岩及古晋带再循环沉积物,Crocker组主要源自婆罗洲西部和马来半岛东部中生代火成岩,以及沙巴本身。Kudat组砂岩物源主要来自沙巴蛇绿岩及部分巴拉望陆块的再循环沉积物。此外,少量始新世岩浆成因碎屑锆石暗示沙巴地区存在始新世与古南海板块俯冲相关的岩浆作用。

Occurrence of Middle Miocene Fossil Cyprinid Fish in the Northern Qaidam Basin and its Paleoenvironmental Implications

With a thick sequence of early Eocene to Pleistocene terrestrial records, the Qaidam Basin on the northern Tibetan Plateau provides an important sedimentary archive for understanding the paleoenvironmental evolution of the northeast Tibetan Plateau. In this study, specimens of fossil fish remains are collected from the late Middle Miocene（Serravallian, -12 Ma） of the middle member of the Shang Youshashan Formation, Dahonggou（DHG） section, in the northern Qaidam Basin. Based on a systematic study of these materials, the remains have assigned to Cyprinidae, with typical pharyngeal teeth and dorsal fin spines with serrations on the posterior edge. Our discovery improves understanding of the cyprinid fish distribution characteristics in the Qaidam Basin during the Cenozoic. Cooccurrences of terrestrial brackish ostracod species Cyprideis and long chain alkenonesin the layer indicate that the studied cyprinid fish lived in a generally large brackish to saline water body during the late middle Miocene（Serravallian）, when the climate of Qaidam Basin was still not sufficiently dry to form an extreme saline water lake.

藏南札达盆地上中新统—上新统托林组介形类群落

笔者在西藏南部札达盆地新生代沉积地层中获得了丰富的介形类化石,根据介形类动物群在地层剖面上的分布规律,建立了两个介形类组合带:(1)Ilyocypris bradyi-Cyclocypris orum-Leucocythere dorsotuberosa组合带;(2)Leucocytherella-Candoniella zadaensis-Leucocythere mirabilis组合带。通过对研究区介形类组合带与国内外其他地区相同层位的介形类组合对比研究,将札达盆地托林组的时代厘定为中新世晚期—上新世最晚期。根据介形类动物群在剖面上的分布规律,自下而上建立了7个介形类群落:Candona-Candoniella群落;Ilyocypris-Cyclocypris群落;Leucocythere-Candona群落;Ilyocypris-Leucocythere群落;Leucocythere-Leucocytherella-Candona群落;Leucocythere mirabilis-Candona群落和Ilyocypris-Leucocytherella群落。通过对介形类群落详细的特征分析并结合磁性地层年代学数据,将札达盆地9.5~1.7 Ma的古气候划分为6个期次:(1)9.5~8.4 Ma为凉湿期;(2)8.4~6.3 Ma为温湿期;(3)6.3~5.5 Ma为凉湿期;(4)5.5~4.4 Ma为温湿期;(5)4.4~2.8 Ma为冷湿期;(6)2.8~1.7 Ma为温暖偏干期。将研究区9.5 Ma以来的气候演化特征与全球气候演变对比认为:札达盆地9.5~6.3 Ma间的气候以暖湿为主,可能与来自印度的东南季风加强有关;6.3~3.6 Ma间札达盆地古气候分析显示为相对暖湿期,存在气候波动,可能与来自印度洋的东南季风再次加强有关;3.6 Ma以后由于受全球气候变冷、冬季风加强及青藏高原强烈隆升的影响,札达盆地气候向寒冷干旱的环境转变,在2.8~1.7 Ma气候却变得温暖潮湿。