分类： 图书馆学、情报学 >> 情报学 提交时间： 2017-08-24
摘要： 虚拟现实技术近几年发展迅速，本文通过分析专利申请、专利权人、专利布局和热点技术等专利情报，为我国企业和相关科研机构进行技术研发和布局提供参考。
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： We study the energy level statistics of the states in U(5) and O(6) dynamical symmetries of the interacting boson model and the high spin states with backbending in U(5) symmetry. In the calculations, the degeneracy resulting from the additional quantum number is eliminated manually. The calculated results indicate that the finite boson number N effect is prominent. When N has a value close to a realistic one, increasing the interaction strength of subgroup O(5) makes the statistics vary from Poisson-type to GOE-type and further recover to Poisson-type.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： We study the energy level statistics of the states in E(5) and X(5) dynamical symmetries. The calculated results indicate that the statistics of E(5) symmetry is regular and follows Poisson statistics, while that of X(5) symmetry involves two maxima in the nearest neighbor level spacing distribution P(s) and the ∆3 statistics follows the GOE statistics. It provides an evidence that the X(5) symmetry is at the critical point exhibiting competing degrees of freedom
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： In the presence of background fields that spontaneously violate Lorentz invariance, a matter-antimatter asymmetry can be generated even in thermal equilibrium. In this paper we systematically investigate models of this type, showing that either high-energy or electroweak versions of baryogenesis are possible, depending on the dynamics of the Lorentz-violating fields. In addition to the previously-studied models of spontaneous baryogenesis and quintessential baryogenesis, we identify two scenarios of interest: baryogenesis from a weak-scale pseudo-Nambu-Goldstone boson with intermediate-scale baryon-number violation, and sphaleron-induced baryogenesis driven by a constant-magnitude vector with a late-time phase transition.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： We explore the possibility that the observed baryon asymmetry of the universe is the result of an earlier phase transition in which an extended gauge sector breaks down into the SU(3)C × SU(2)L × U(1)Y of the Standard Model. Our prototypical example is the Topflavor model, in which there is a separate SU(2)1 for the third generation from the SU(2)2 felt by the first two generations. We show that the breakdown of SU(2)1 × SU(2)2 → SU(2)L results in lepton number being asymmetrically distributed through-out the three families, and provided the SM electroweak phase transition is not strongly first order, results in a non-zero baryon number, which for parameter choices that can be explored at the LHC, may explain the observed baryon asymmetry.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： As the surface magnetic field in niobium cavities approaches the theoretical critical field, RF losses grow sensitive to increasingly subtle features of the material and the surface. A striking example is the familiar onset of the high field Q-slope, where RF losses increase exponentially with field. A surprising feature of the high field Q-slope is its positive response to a mild baking at 100-120 鈼. But the Q-slope returns after the first 20 nm of the niobium metal surface is converted to loss-less pentoxide via anodization. The latter result suggests that the cause of the fast growing losses resides in the first 20 nm of the RF surface. Although there are several propositions, the exact mechanism for the high field Q-slope is not yet fully understood and demands further research. We are conducting surface analytic studies with optical profilometry, EBSD, XPS, Auger and SIMS to shed light on the mechanism of the high field Q-slope. We are comparing the behavior of fine-grain niobium with single crystal niobium, buffered chemical polishing (BCP) treatments with electropolishing (EP) treatments and properties before and after 110 鈼 bake. Our approach is based on identifying lossy regions, dissecting of these regions and range of analysis.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： We study the properties of g 1 , the first excited state of the gluon in representative variants of the Randall Sundrum model with the Standard Model fields in the bulk. We find that measurements of the coupling to light quarks (from the inclusive cross-section for pp → g 1 → tt), the coupling to bottom quarks (from the rate of pp → g 1 b), as well as the overall width, can provide powerful discriminants between the models. In models with large brane kinetic terms, the g 1 resonance can even potentially be discovered decaying into dijets against the large QCD background. We also derive bounds based on existing Tevatron searches for resonant tt production and find that they require Mg 1 & 950 GeV. In addition we explore the pattern of interference between the g 1 signal and the non-resonant SM background, defining an asymmetry parameter for the invariant mass distribution. The interference probes the relative signs of the couplings of the g 1 to light quark pairs and to tt, and thus provides an indication that the top is localized on the other side of the extra dimension from the light quarks, as is typical in the RS framework.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： If a new massive vector boson with nonzero axial couplings to fermions will be observed at LHC, then an upper limit on the scale of new physics could be derived from unitarity of S-matrix. The new physics will involve either new massive fermions, or scalars, or even a strongly coupled sector. We derive a model independent bound on the scale of new physics. If MG/g A < 3 TeV and the fermion is a top quark, the upper limit is 78 TeV.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： In the presence of background fields that spontaneously violate Lorentz invariance, a matter-antimatter asymmetry can be generated even in thermal equilibrium. In this paper we systematically investigate models of this type, showing that either high-energy or electroweak versions of baryogenesis are possible, depending on the dynamics of the Lorentz-violating fields. We identify two scenarios of interest: baryogenesis from a weak-scale pseudo-Nambu-Goldstone boson with intermediatescale baryon-number violation, and sphaleron-induced baryogenesis driven by a constant-magnitude vector with a late-time phase transition.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： We explore the possibility that the right-handed top quark is composite. We examine the consequences that compositeness would have on tt production at the Tevatron, and derive a weak constraint on the scale of compositeness of order a few hundred GeV from the tt inclusive cross section. More detailed studies of differential properties of tt production could potentially improve this limit. We find that a composite top can result in an enhancement of the tttt production rate at the LHC (of as much as 103 compared to the Standatd Model four top rate). We explore observables which allow us to extract the four top rate from the backgrounds, and show that the LHC can either discover or constrain top compositeness for wide ranges of parameter space.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-24
摘要： We study the decay of a Z ′ boson into two Z bosons by extending the Landau-Yang theorem to a parent particle decaying into two Z bosons. For a spin-1 parent the theorem predicts: 1) there are only two possible couplings and 2) the normalized differential cross-section depends on kinematics only through a phase shift in the azimuthal angle between the two decay planes of the Z boson. When the parent is a Z ′ the two possible couplings are anomaly-induced and CP-violating, respectively. At the CERN Large Hadron Collider their effects could be disentangled when both Z bosons decay leptonically
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： The transformation from a long reptilian tail to a shortened tail ending in a pygostyle and accompanied by aerodynamic fanning rectrices is one of the most remarkable adaptations of early avian evolution. However, no fossils directly capture this transition, and information regarding the structural morphology and the early evolution of the pygostyle in Mesozoic birds and their integuments is relatively limited. Here we provide a review of the pygostyle morphology of Early Cretaceous birds with comparison to the structure in living birds. This study emphasizes the convergent evolution of distally co-ossified caudal vertebrae in non-avian maniraptorans and early birds. There further exist distinct differences in pygostyle morphology between Sapeornithiformes, Confuciusornithiformes, Enantiornithes, and Ornithuromorpha. The morphology of the pygostyle and rectrices in early ornithuromorphs appear similar to that of extant birds, whereas the pygostyle in more primitive birds does not appear morphologically capable of supporting the rectricial bulbs and musculature necessary to control an aerodynamic fan-shaped tail. The rectricial bulbs and rectricial fan appear to have coevolved with the plough-shaped pygostyle early in the evolution of the Ornithuromorpha. This study also shows that the confuciusornithiform pygostyle was more similar to that of enantiornithines than previously recognized, consistent with the presence of nearly identical ornamental tail feathers in both groups. 从兽脚类恐龙中爬行类的骨质长尾，到以尾综骨为终端，并附着具有空气动力学功能的扇状尾羽的短巧尾部，是早期鸟类演化中最显著的适应性转变之一。但能直接反映这一转变的化石记录匮乏，而且对中生代鸟类尾部形态结构，以及尾综骨和尾羽早期演化的认知也相对不足。在此对早白垩世鸟类的尾综骨形态予以概述并将其与现生鸟类尾部结构类比。本研究强调了非鸟手盗龙类中尾椎的联合骨化与早期鸟类的尾综骨实属趋同演化。本研究表明，会鸟形类、孔子鸟形类、反鸟类和今鸟型类的尾综骨结构存在明显差异。今鸟型类尾综骨和尾羽(舵羽)与现代鸟类的相似，而相对更原始的鸟类的尾综骨，从形态来看，并不能支持舵羽球状膨大和必要的肌肉附着来操控具有空气动力学功能的扇状尾羽。由此可见，舵羽球状膨大、舵羽扇面与犁铧状的尾综骨是在今鸟型类演化早期相伴相生的。相对于从前的认知，本研究还发现孔子鸟类的尾综骨与反鸟类的有更多相似之处，与二者都具有的几乎相同的装饰性尾羽相符合。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： A new species of large Irdinmanhan brontothere, Epimanteoceras mae sp. nov., is described based on an incomplete skull which was collected from the Üqbulak Formation of Sangequan site, Junggar Basin of Xinjiang Uygur Autonomous Region. The new specimen can be assigned to the genus Epimanteoceras by the large superorbital processes, the broad frontal bone, the shallow central fossae on the molars, and the absence of the anterolingual cingular cusp on molars and the hypocone on M3. E. mae is characterized by the slightly laterally bowed zygomatic arches, the medially arched parasagittal ridges, the posteromedially angled external auditory pseudomeatus, and the prominent occipital pillar processes. E. mae and E. formosus are closely related. It is uncertain whether E. mae or E. formosus forms the sister group to Brontotheriina, but both of them are the basal group of the latter in the phylogenetic analysis. They are both closed to the Irdinmanhan brontothere Protitan grangeri from Nei Mongol but much primitive than Aktautitan hippopotamopus from Kazakhstan. The discovery of E. mae in Sangequan indicates that the age of Üqbulak Formation is Middle Eocene, and earlier than that of Kyzylbulak Formation bearing A. hippopotamopus in Kazakhstan. Moreover, the discovery of E. mae in Xinjiang expanded the distribution of the genus Epimanteoceras, which was only found in Nei Mongol previously. 新疆准噶尔盆地三个泉中始新世依希白拉组内发现的晚叉额雷兽属新种－马氏晚叉额雷兽(Epimanteoceras mae sp. nov.)是新疆目前发现保存最好的雷兽头骨化石。标本为一件不完整的头骨，缺失鼻骨，前颌骨，部分上颌骨和泪骨。新种具有眶上突较粗大，额骨宽阔平坦，臼齿有中心窝，臼齿舌侧齿带前部上的齿尖不发育，M3无次尖等晚叉额雷兽属的特征。新种的颧弓成向外扩的弓形，额顶嵴在后侧向内收缩弯曲的弧度更大，外耳道较为倾斜，枕柱上方有舌状的突起，与唯一的属型种娇晩叉额雷兽(Epimanteoceras formosus)明显不同。马氏晚叉额雷兽同属型种关系最近，两者在系统发育分析中同为雷兽亚族(Brontotheriina)的基干类群，但是两者是否为后者的姊妹类群尚无法确定。和属型种一样，马氏晚叉额雷兽在演化程度上与内蒙古伊尔丁曼哈期的谷氏原雷兽(Protitan grangeri)接近，但与同时期地理位置更近的哈萨克斯坦的雷兽Aktautitan hippopotamopus相比，马氏晚叉额雷兽较原始，表明新种所在的地层时代很可能要早于发现A. hippopotamopus地层。三个泉剖面依希白拉组伊尔丁曼哈期内以前发现的化石较少，此次马氏晚叉额雷兽的发现，不仅扩大了晚叉额雷兽属的地理分布，亦为依希白拉组内存在伊尔丁曼哈期的沉积提供了新的佐证。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： New findings of galeaspids (Agnatha) including Altigibbaspis huiqingae gen. et sp. nov., an indeterminate polybranchiaspid, Eugaleaspis changi, and Nanpanaspis microculus are described from the lower part of the Xishancun Formation (early Lochkovian, Early Devonian) near the northeast entrance of Liaokuo Park, Qujing City, Yunnan Province, China. The Polybranchiaspis-like new genus is characterized by a blade-like median dorsal ridge on the dorsal side of head-shield. The morphological disparity of the median dorsal ridge and spine in galeaspids suggests that these structures functioned more than providing a hydrodynamic stability. We assume that a high upright and compressed spine may render galeaspid fishes an apparently larger size as seen by a predator, and a blade-like median dorsal ridge may accomplish a defense against the claws of large sea scorpions. Nanpanaspis is peculiar in bearing two short laterally projecting processes on each side of the head-shield, and its phylogenetic relationship is discussed based on different interpretations on the homology of these processes. Considering the unique morphology of Nanpanaspis, and its early occurrence among the Huananaspiformes, we assign Nanpanaspis in the monogeneric family Nanpanaspidae to represent an early branch of the Huananaspiformes. 本文描述了云南曲靖早泥盆世西山村组盔甲鱼类(无颌类)的新发现，包括一新属、新种——惠清驼背鱼(Altigibbaspis huiqingae gen. et sp. nov.), 一件属种未定的多鳃鱼科标本，以及张氏真盔甲鱼(Eugaleaspis changi)和小眼南盘鱼(Nanpanaspis microculus)的新材料。驼背鱼在很多方面跟多鳃鱼都非常相似，但头甲背面具一特征性的驼背状隆起，其上有一刀刃状的中背脊。中背脊和中背棘在盔甲鱼类里的形态分异度表明：它们除了能够提供游泳方向稳定性外，可能衍生出了一些附加的功能，例如直立高耸的中背棘能使盔甲鱼在捕食者眼里具有了恐吓性，刀刃状的中背脊可能也起到一些防御的作用。南盘鱼头甲侧缘具有两对非常奇特的侧向延伸的突起；通过对这两对侧突同源性的比较，讨论了南盘鱼的潜在系统分类位置。鉴于南盘鱼奇特的形态，以及它在华南鱼目中相对较早的出现时代，建议暂时把南盘鱼放到一个单属科南盘鱼科，代表了华南鱼目早期分出来的一个支系。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： 嵌齿象是真象的基干类群，其研究历来受到重视，同时也存在很多争议。维曼嵌齿象(Gomphotherium wimani)是中国的一个特有种，之前仅有一些牙齿和破碎下颌的报道，研究者对其形态特征和演化地位的认识一直比较模糊。本文报道了发现于甘肃省临夏盆地的维曼嵌齿象的新材料，包括上沟地点一件未成年头骨和倒黑沟地点属于同一个体的部分颊齿。通过研究对比，认为维曼嵌齿象是嵌齿象中一个比较进步的种，具有如下独有特征：颊齿的主齿柱前后中心小尖分裂并成嵴状，副齿柱趋向于分裂，发育有弱的副齿柱中心小尖，齿谷中等开阔，齿冠相对较高。对过去发现的维曼嵌齿象材料的厘定表明，该种最初建立时产于泉头沟地点的一颗m3实际上是葛氏铲齿象(Platybelodon grangeri)的M3; 而西宁吊沟地点发现的维曼嵌齿象的一件M3极有可能属于铲齿象类(amebelodontids)。对厘定后的维曼嵌齿象地点的研究表明，维曼嵌齿象分布于中国甘肃、青海的几个中中新统地点，其时代基本上可以与MN6−MN7/8早期相对比，时代跨度估计为15~13 Ma。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： The diets and environments of fossil rhinocerotoids from the Linxia Basin, Gansu, China, ranging in age from 25 to 2.5 Ma, were reconstructed based on bulk and serial carbon (C) and oxygen (O) isotope analyses of tooth enamel. The results support many previous hypotheses inferred from dentition and cranial and limb morphology and offer new insight on the paleoecology of some genera. The isotopic results support the following previous hypotheses: the Late Oligocene rhino Paraceratherium inhabited a forested environment, and the coexisting rhino Allacerops lived in a relatively open habitat and had a less specialized diet; the Middle Miocene Hispanotherium grazed in open territory, whereas the contemporaneous Alicornops had a more generalized diet in a forested environment; and the Late Miocene rhino Parelasmotherium grazed in an open steppe habitat. The isotope data indicate that the rhinos Acerorhinus and Dicerorhinus inhabited open steppe environments, inconsistent with previous inferences that these two rhinos dwelled in forested environments. The isotopic results are not conclusive concerning the habitat of Iranotherium, but support previous hypotheses that this rhino was a specialized C3 grazer. The results also suggest that Chilotherium was a forest-dweller throughout much of the Late Miocene, but occupied a more open environment by the end of the Late Miocene. Additionally, the results are consistent with previous hypotheses that the Pliocene rhino Shansirhinus and the Pleistocene rhino Coelodonta were grazers in open habitats. Finally, the C isotope data support that all rhinos in this study were pure C3 feeders, confirming that C4 grasses were not an important component of the plant biomass in the Linxia Basin from 25 to 2.5 Ma. 根据牙齿釉质的全样和系列碳、氧同位素分析，重建了甘肃临夏盆地25~2.5Ma期间犀牛的食性和环境。其结果支持先前根据牙齿和头骨-肢骨形态做出的一些推断，并对部分属的古生态提出了新的看法。同位素结果支持如下的推断：晚渐新世的巨犀Paraceratherium生活于森林环境，而与其共生的异角犀Allacerops栖息地相对开阔，食性特化程度低；中中新世的西班牙犀Hispanotherium在开阔领地上取食草本植物，而同时代的奇角犀Alicornops在森林环境中具有更特化的食性；晚中新世的副板齿犀Parelasmotherium在开阔的稀树草原上取食草本植物。与先前认为无鼻角犀Acerorhinus和额鼻角犀Dicerorhinus生活于森林化环境的推断不同，数据指示这两种犀牛也生活于开阔的稀树草原环境。同位素结果未能得出伊朗犀Iranotherium的确切生活环境，但支持先前认为它特化为C3草本植物取食者的推断。研究结果也显示大唇犀Chilotherium在晚中新世的大多数时间内是森林生活者，但其在晚中新世末期占据了更开阔的环境。此外，分析结果与先前的推断一致，即上新世的山西犀Shansirhinus和更新世的披毛犀Coelodonta是开阔生活环境中的食草者。最后，碳同位素数据支持在此项研究中的所有犀牛都是纯C3取食者，确认C4植物不是临夏盆地从25Ma到2.5Ma期间植被的重要成分。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： Regalerpeton weichangensis was established in 2009 on an incomplete skeleton preserved mainly as an impression from the Lower Cretaceous of Hebei, China. However, several anatomical characters were misinterpreted due to distortion of the holotype, and its taxonomic position has been in debate. In this paper, R. weichangensis is redescribed based on eight new specimens and its diagnosis and phylogenetic position are re-examined. This work shows that R. weichangensis was a neotenic form with ossified carpals and tarsals. It has a series of unique combination of characteristics including the vomer with a transverse vomerine tooth row, anterior end of the cultriform process of the parasphenoid indented, basibranchial II triradiate and scapulocoracoid with a rectangular coracoid end. Phylogenetic analysis suggests Regalerpeton, Jeholotriton and Pangerpeton should be placed in the suborder Salamandroidea with three synapomorphies. Moreover, they also share unicapitate ribs with Cryptobranchoidea, which indicates that they represent an important stage of evolution in the Cryptobranchoidea-Salamandroidea split. 围场皇家螈(Regalerpeton weichangensis)于2009年基于一件产自河北围场下白垩统不完整的骨骼印痕标本命名。然而由于标本变形导致皇家螈的部分解剖学特征被曲解，系统发育位置也存在争论。本文基于八件新标本对该蝾螈的鉴定特征和系统发育位置进行了修订。研究显示，皇家螈是一种腕骨和跗骨骨化的幼态持续型蝾螈，具有独特的特征组合，包括犁骨齿列横向排列、副蝶骨前端呈齿状、基鳃骨II呈三射型以及肩胛乌喙骨的乌喙端呈矩形。新的系统发育分析根据三个近裔共性将围场皇家螈、热河螈和胖螈归入蝾螈亚目。此外，它们还与隐鳃鲵亚目共有“肋骨单关节头”这一特征，显示这三种蝾螈可能代表了隐鳃鲵亚目与蝾螈亚目分离时期这一重要演化阶段。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： Remains of Platacanthomyidae from a late Cenozoic fissure in Fanchang, Anhui, and from the Miocene deposits of Sihong, Jiangsu, China are described. Three species and two genera, including two new species are recognized. They are Neocometes sinensis sp. nov. from Fanchang and Sihong, and N. magna sp. nov. and Typhlomys sp. from Fanchang. The Fanchang assemblage is a mixed sample with elements probably representing an interval spanning from the Early Miocene to the Pleistocene. Judging from fossil content and coloration in the sample, the two species of Neocometes are inferred to be Miocene in age, while the Typhlomys to be later. The joint occurrence of some typical Miocene elements in the assemblage seems to indicate that the Fanchang sample includes an association which can be closely correlated with the Early Miocene Sihong Fauna and the Shanwang Fauna of China, and with the Miocene faunas known from Thailand. Dental characters of Neocomets appear to suggest that the Asian species of the genus have undergone a rapid increase of size, heightening of dental crown, strengthening of ridges, and gradually development of ectoloph in the upper molars and endolophid in the lower molars, representing an evolutionary lineage different from that of Europe. 描述了安徽繁昌和江苏泗洪新发现的晚新生代堆积物中的刺山鼠科化石。化石共有两属3种，即产自安徽、江苏的中华新来鼠(新种) (Neocometes sinensis sp. nov.)和产自安徽的大新来鼠(新种) (N. magna sp. nov.)及猪尾鼠未定种(Typhlomys sp.)。安徽繁昌的材料来自裂隙堆积，采样时未作分层处理，对单个化石属种很难进行准确的时代确定；但根据所采集化石的组分和上下层位保存的颜色与埋葬方式上的差异，推测Neocometes的时代为中新世，而Typhlomys可能较晚。Neocometes属的出现和典型中新世动物成员的存在，表明繁昌这一含古猿的裂隙堆积中含有大致与江苏泗洪动物群和山东山旺动物群相当、甚至可与泰国中新世动物群对比的啮齿动物组合。新种牙齿的形态特征显示，Neocometes属在亚洲经历了个体迅速增大，齿冠增高，齿脊增强，上臼齿外脊和下臼齿内脊逐渐发育的过程，与该属在欧洲的演化趋势有所不同。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： The new fossils of Bos primigenius in this study came from two regions in Hebei Province: Nihewan Basin (one partial skull with right horn-core and one humerus) and Longhua County (one humerus, one tibia, 2 calcanea and 3 astragali). The humerus from Nihewan has a total length of 457.3 mm, which almost represents the largest aurochs individual which has a two-meter shoulder height. The biggest humerus and other big cranial specimens in northern China can be correlated with the European counterparts of late Middle Pleistocene, and they should be contemporary. The smaller sized limb-bones from Longhua were unearthed from loess deposits, which can be attributed to Late Pleistocene. The current knowledge shows that aurochs may have arrived in China earlier than Late Pleistocene, because its associated taxa, e.g. Canis lupus, Panthera tigris, Mammuthus primigenius, Equus caballus, Coelodonta antiquitatis, Sus scrofa, Camelus knoblochi, Cervus elaphus, Alces alces and Bison priscus have appeared as early as late Middle Pleistocene or even earlier in Eastern Europe and Northern Eurasia. Furthermore, new numerical dating results show that the aurochs’ occurrences from some sites in China can be traced back to Middle Pleistocene. This study proposes that the larger sized aurochs should be of a late Middle Pleistocene age. In China, aurochs fossils mainly occur in the northern part and the transitional zone along the Huaihe River, but are absent in southern China and Southeast Asia, which resulted in the hypothesis of “Central Asian Corridor” through which aurochs reached China. In recent years as more bovini fossils were recovered in Africa, the Bos phylogeny was proposed, which assumed that the evolution of Bos lineage took place in Africa rather than in Eurasia as thought before, and the earliest ancestor of B. primigenius is Pelorovis turkanensis, finally the genus Bos dispersed into Eurasia at the beginning of the Middle Pleistocene. The present authors think that the African Pelorovis species are too different from the Bos lineage in morphology; on the contrary, the early Bos species from Siwalik in South Asia resembles B. primigenius very much. In China, most of the B. primigenius fossils were recovered from fluvio-lacustrine deposits in North China Plain, Loess Plateau and Song-Nen Plain, whereas few of them were from loess deposit, which means that the aurochs fossils could be employed as an indicator of warm climate and wet environment. 原始牛(Bos primigenius)化石新材料包括泥河湾盆地禾尧庄的1件角心、上沙嘴的1件肱骨和承德隆化的1件肱骨、1件胫骨、1件踝骨、2件跟骨和3件距骨；其中上沙嘴的肱骨化石长达457.3 mm, 代表迄今在我国境内发现的最大原始牛个体，也是该种的最大记录之一，推算其所属动物的肩高接近2 m; 北京门头沟珠窝的原始牛头骨的眶后宽度及角心周长数据也是该种的最大记录之一；禾尧庄的角心标本稍小，但也比晚更新世多数同类要大；这些巨大的化石与欧洲中更新世晚期同类十分接近，其时代也应当与之相当，为中更新世晚期；过去认为原始牛在我国只出现于晚更新世地层，但现在看来该种在中更新世晚期就已扩散到中国。东欧及北亚的最新化石证据表明，过去认为与原始牛共生的晚更新世化石组合的常见属种早在中更新世晚期或更早时期就已出现，其中包括灰狼、虎、真猛犸象、马、真披毛犀、野猪、诺氏驼、赤鹿、驼鹿及草原野牛等。最新测年数据也表明中国北方有几个含原始牛化石的遗址是形成于中更新世晚期；本文认为华北和西北地区个体巨大的原始牛，代表中更新世晚期，而个体较小的则可能代表晚更新世或全新世；近些年在东北地区发现大量原始牛化石，但其中少见个体巨大者。在我国，原始牛化石分布只局限于北方及淮河过渡区，而在南方及毗邻的东南亚地区均未发现此类化石；因此，有人提出原始牛很可能是在中更新世中、晚期通过中亚走廊(Central Asian Corridor)进入中国。不过，近些年在非洲也发现了一些牛属(Bos)化石，因此有人又提出了牛属非洲起源的“奥杜威牛–牛属演化谱系”(Pelorovis–Bos lineage), 但该学说所依据的奥杜威牛化石材料，在形态结构上与牛属相去甚远，难以归入同类；此外，非洲可靠的牛属化石记录均未超过1 Ma。本文作者支持传统的牛属“南亚起源学说”，因为在南亚西瓦里克地区发现的早期牛属化石不仅时代更古老(早于2 Ma), 并且在形态上与原始牛更为相似。中国北方的原始牛化石主要发现于华北平原、黄土高原和松嫩平原的河湖相堆积层，仅极个别出现于黄土地层；由此推断原始牛可能更喜欢水系发育的林缘和/或沼泽环境。
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： The present paper revalidated Asiatosuchus nanlingensis Young, 1964 and Eoalligator chunyii Young, 1964 in taxonomy based on a detailed comparative study on those relevant specimens. New information derived from this study revealed that A. nanlingensis and E. chunyii were truly distinguishable from each other and therefore, diagnosis was further revised for each of them. A. nanlingensis is large, with a moderately long or a very elongate snout, and characterised mainly by the combination of the following characters such as: the quadrate with a lateral condyle much larger than the medial one, the surangular pinched off before reaching the end of the retroarticular process, the dental margins (at least the posterior portion) of the jaws nearly straight, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. E. chunyii is a median-sized, short-snouted animal and characterised mainly by the combination of the following characters such as: the condyles of the quadrate similar in size, the dental margins of the jaws strongly concavo-convex, the dentary symphyses very short, the splenial not entering the mandibular symphysis, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. With new information derived from this study, the phylogenetic relationships of A. nanlingensis and E. chunyii were tested, which did not support the view that the two species formed a monophyletic clade and opposed that E. chunyii could be considered as the synonym of A. nanlingensis. 根据对有关标本的详细对比研究，重新评估了南岭亚洲鳄(Asiatosuchus nanlingensis Young, 1964)和存义始猛鳄(Eoalligator chunyii Young, 1964)的分类。获得的新信息表明这两种是可以彼此区分的，因此对它们各自的鉴定特征进行了进一步修订。南岭亚洲鳄是个大型种类，它很可能具有中等或很长的吻部(眶前段), 主要由以下一些特征组合界定：方骨外髁比内髁大很多，上隅骨在反关节突近端尖灭，上、下颌齿缘(至少后段)几近平直，以及在下颌关节窝外侧上隅骨表面具一凹或纵沟。存义始猛鳄是个中型种类，主要可以由下列特征组合界定：方骨内、外关节髁大小几近相当，上、下颌齿缘强烈凹凸不平，齿骨联合很短，夹板骨不进入下颌联合，以及在下颌关节窝外侧上隅骨表面具一凹或纵沟。根据新的信息对南岭亚洲鳄和存义始猛鳄原来的系统关系进行了检验，所得结果不支持南岭亚洲鳄和存义始猛鳄可以形成一单系分支及反对后者是前者的同物异名。虽然本文研究表明南岭亚洲鳄可以和其他种类区分，但是在系统关系上却不能和亚洲鳄典型种(葛氏亚洲鳄Asiatosuchus grangeri)归于同一支系，如此应该为其建立一属。然而，鉴于南岭亚洲鳄标本太不完整，在没有新的、更完整的标本发现之前，本文仍沿用其原名，如德国亚洲鳄(Asiatosuchus germanicus)一样，后者也不和亚洲鳄典型种归于同一支系。
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