蒙古新发现的渐新世山河狸和松鼠类化石(英文)

蒙古中部地区的三达河组(HsandaGolFormation)是亚洲渐新世陆相地层的经典地层之一。三达河组的沉积岩层现被分成两个岩性段:上部早渐新世晚期-?晚渐新世山地段(ShandMember)和下部早渐新世早期塔塔尔段(TatalMember);两岩段间有时夹有KharKhoroo玄武岩层(BryantandMcKenna,1995;MengandMcKenna,1998)。该玄武岩层的时代用40Ar/39Ar法被确定为距今31.5Ma(Hcketal.,1999,他们称其为BasaltI)。三达河组中产有丰富的哺乳动物化石,特别是啮齿类化石(MatthewandGranger,1923;Kowalski,1974;RussellandZhai,1987;Hcketal.,1999)。近年来,本文的后一作者在三达河组中又采集到一批啮齿类化石,其中包括松鼠和山河狸2科的化石。本文是对这两类化石新材料的记述。现生的松鼠科分异很大,而且大多数都分布在亚洲。然而,松鼠科化石在古近纪时在北美和欧洲却很丰富。在北美出现于晚始新世,在渐新世时已明显分异;在欧洲出现于早渐新世,在中新世时分异很大。相反,亚洲古近纪的松鼠化石却发现得很少,标本也很破碎。已报道的只有3件标本。2件产自党河下游地区:Bohlin(1946)报道的晚渐新世的Sciurussp.,标本只是2枚单个臼齿(M3和m2);王伴月、邱占祥(2004)报道的早渐新世的党河鲜松鼠(Oligosciurusdangheensis),标本只是一段带m1～2的下颌骨。还有一件是Minjin(2004)报道的蒙古渐新世的三达河克热姆鼠(Kheremhsandgoliensis),标本也只是一段带m1～3的下颌骨。本文报道的松鼠化石产自蒙古国的巴彦洪戈尔省的塔石盖贝(TashgainBel)地点的三达河组上部山地段,时代为早渐新世晚期-?晚渐新世。这批松鼠化石标本包括1件具P3～M3的上颌骨(PC369)和2段下颌骨(PC3610和PC3611)。这是亚洲古近纪目前已知的最好的一批松鼠化石标本,代表松鼠科Kherem属的一新种:亚洲克热姆鼠(Kheremasiaticasp.nov.)。其主要特征是颊齿较大,较宽;下内尖的高度和下次尖的大小从m1到m3变化不大,彼此相近;下内脊较明显;下内尖较明显,与下后边脊间有浅沟分开等。K.asiatica的形态特征表明,Kherem属应归入北美的Cedromurinae亚科。新的发现表明,亚洲渐新世的松鼠已发生了分异,至少可分为3支。以Kherem为代表的一支,与北美早期的cedromurines有较近的系统关系。它可能是由类似于北美Oligospermophilus的种类演化并迁徙到亚洲来的。现生的山河狸只有一种(Aplodontiarufa),仅生活在北美西部沿海地区。但从始新世到中新世,山河狸却遍布全北区。它们在北美较繁盛,分异大,但在亚洲发现得很少。在亚洲渐新世地层中虽曾报道过3属4种山河狸化石,但材料都很少(Prosciurusordosicus和P.?shantungensis均只有一枚单个的牙)。山河狸化石在蒙古渐新世地层的新发现表明,亚洲渐新世的山河狸化石比已知的要丰富。本文描述的山河狸化石分别采自蒙古南戈壁省Shunkt地点的山地段和前杭爱省UlaanKhongil(=TatalGol)地点的塔塔尔段。它们代表原松鼠属的3类:蒙古原松鼠(新种)(Prosciurusmongoliensissp.nov.)、蒙古原松鼠(相似种)(P.cf.P.mongoliensis)和小原松鼠(新种)(P.pisinnussp.nov.)。蒙古原松鼠的主要特征是下颊齿的下中附尖与下后附尖脊连,下中尖发育较弱,下外中脊弱或无;p4无下前边尖和下前齿带;m1具从下外脊伸向下次脊的小刺;m2和m3的下后脊II较发育;下次脊在p4和m1后弯,与下后边脊连,在m2和m3横向,伸达下外脊等。蒙古原松鼠(相似种)与蒙古原松鼠的区别是:颊齿尺寸较小,p4具明显的下外中脊,p4和m1的下次脊弯曲度较缓,m1缺从下外脊伸向下次脊的小刺,m2～3的下后脊II较短等。小原松鼠的主要特征是:个体较小;齿冠较低;下臼齿的下中附尖孤立;下颊齿的下次脊横向、较低,与下外脊连,下中尖和下外中脊均较明显,下次尖明显向前颊侧延伸,具明显的齿带等。蒙古渐新世啮齿类化石的新发现表明,亚洲渐新世的松鼠和山河狸与北美的关系要比与欧洲的近。     

内蒙古四子王旗额尔登敖包晚始新世紧齿犀类一新属(英文)

描述了内蒙古四子王旗额尔登敖包晚始新世乌兰戈楚组(?)(中白层)的紧齿犀亚科(Eggysodontinae)一新属种:邱氏原紧齿犀(Proeggysodon qiui),标本为破损的下颌骨。新属种与其他渐新世紧齿犀的区别在于个体较小,具有两对发育的铲形下门齿,下前臼齿没有臼齿化,p4的下斜脊更向舌侧倾斜延伸,下臼齿下斜脊与下次脊连接处呈角状,下臼齿无颊侧齿带。紧齿犀类和柯氏犀类(forstercooperes)可能有较近的系统发育关系,它们具有以下的共近裔性状:短而粗壮的大犬齿,相对短的齿隙(犬齿和前臼齿之间),下颌联合部短而高,从而使门齿趋向直立。新标本的发现填补了早-中始新世柯氏犀类和渐新世紧齿犀类在时代上的空白,也使紧齿犀类成为欧洲始新世/渐新世之交的"大间断"之后哺乳动物群自亚洲迁入欧洲的又一例证。     

记山东沂南上新世熊属—新种

本文记述了产自山东沂南一洞穴堆积中的熊类化石一新种:Ursus yinanensis。这种熊具有个体较小,前臼齿数目全,下裂齿的下后尖之前尚未出现附尖等原始性特征,它与欧洲早上新世的Ursus boeckhi在进化程度上比较接近但更显进步。这是在中国首次发现的中上新世Ursus的可靠记录,它的发现对于探讨欧亚大陆上真正熊类的演化及地理分布等问题具有重要意义。     

记裂齿目(哺乳动物纲)一新属——豫裂兽(Yuesthonyx gen.nov.)

古新世晚期裂齿类———丁氏豫裂兽 (新属、新种 ) (Yuesthonyxtingaegen .etsp .nov.)的发现表明了裂齿目在亚洲古新世已相当分化 ,在臼齿形态上有与北美始新世Esthonyx相近的小尖兽 (Meiostylogon)和中间兽 (Interogale) ,也有与北美Megalesthonyx接近的豫裂兽等。根据豫裂兽、Megalesthonyx、和亚洲的Adapidium的上臼齿都具有明显的中附尖等特征可与其他裂齿类相区别 ,新建了豫裂兽科 (YuesthoncidaeFam .nov.)。     

柴达木盆地渐新世的鲤科鱼类化石

记述了首次发现于柴达木盆地早渐新世晚期至晚渐新世早期(距今27～29 Ma)的鲤科鱼类化石。材料包括咽骨、咽齿、匙骨、腹鳍骨及一些零散的鳍条。咽骨及咽齿化石与原始鲃亚科鱼类及裂腹鱼亚科裂腹鱼属鱼类的相似;腹鳍骨化石与原始鲃亚科鱼类的更相似。鲃亚科鱼类现今分布于北纬35°以南的亚洲、欧洲南部及非洲北部;裂腹鱼属鱼类分布局限于青藏高原东、南、西面的边缘区域,在柴达木盆地没有分布。柴达木盆地水系现生鱼类仅见适于高寒环境的高度特化等级的裂腹鱼亚科鱼类及鳅科高原鳅属鱼类,鱼类组成与早渐新世晚期至晚渐新世早期的不尽相同。     

山东五图早始新世更猴科(Plesiadapidae,Mammalia)化石

记述了山东五图盆地早始新世五图组的一种更猴类 (plesiadapid)化石 :杨氏亚洲更猴(Asioplesiadapisyoungigen .etsp .nov .)。在它增大的下门齿上具有更猴科特有的下缘尖和下缘脊 ,但其下颊齿性状相当原始 ,p4跟座呈盆状 ,m3下次小尖呈锥状更类似白垩纪晚期出现的更猴形动物Purgatorius。Asioplesiadapis的下臼齿形态可以说明亚洲更猴类虽然有北美和欧洲更猴的某些典型特征 ,但并不在同一进化支系。因此 ,另立一新亚科———亚洲更猴亚科(Asioplesiadapinaesubf.nov.)。     

内蒙乌兰察布盟渐新世古猪兽化石

古猪兽(Archaeotherium)属于猪齿兽科(Entelodontidae)。这科动物至少在始新世晚期时已经生存于亚洲(Matthew and Granger,1925;周,1958)和北美(Cope,1873);到了渐新世广泛分布于北美及欧亚,达到最繁盛的时期;但到中新世初期就完全程灭了。这科动物的身体从早期就迅速地向“大型”发展。渐新世的代表,大小已和现代野猪的相近;到中新世初期时已发展到如现代野牛的大小。这科动物的形态在头骨和牙齿构造某些方面与     

现代中国人群形成与分化的形态证据——亚洲与非洲现代人群上颌第一臼齿齿尖相对面积的对比分析

现代人群形成与分化造成的具有地域差别的人群标志性体质特征是研究人群之间关系的重要信息。作为臼齿形态测量的组成部分,上颌第一臼齿齿尖相对面积在人类演化以及现代人群关系上的研究价值已经引起了人类学界的关注。然而,迄今对上颌第一臼齿齿尖相对面积在世界各地的现代人群之间是否具有地域性差异还不是很清楚。本文对代表亚洲和非洲现代人群的208枚上颌第一臼齿齿尖相对面积的研究发现,上颌第一臼齿四个主要齿尖相对面积在亚洲和非洲现代人群之间都存在明显差异。亚洲现代人上颌第一臼齿近中齿尖(原尖和前尖)相对面积较大,而远中齿尖(后尖和次尖)相对面积较小。非洲现代人上颌第一臼齿各齿尖相对面积均较亚洲人群具有更大的变异,尤其在原尖和次尖相对面积上。采用判别分析可以将69.2%的标本正确地判别归入其原来所属的组群。通过与化石人类相关数据的对比发现,非洲现代人比亚洲现代人在原尖和次尖相对面积以及前尖/后尖相对面积比例上更加接近于人类演化的早期形式。现有的证据显示,亚洲和非洲现代人群在齿尖相对面积的分化至少可以追溯到全新世早期,更加精确的分化时间需要结合更新世晚期甚至中期化石人类数据去获得。本研究揭示出的非洲现代人上颌第一臼齿齿尖相对面积的高异质性(heterogeneity)和相对原始性在现代人形成与分化方面的作用尚需进一步的研究。     

记甘肃广河晚中新世祖熊头骨化石（英文）

记述了一件与下颌咬合在一起的完整的祖熊头骨化石。化石发现于甘肃临夏州广河县槐沟村柳树组地层中上部,其层位与时代为新近纪灞河阶/期的晚期,距今约8 Ma。对比研究表明,该头骨与目前所有已知熊类祖先类型都不同,应为一新种,定名为Ursavus tedfordi(戴氏祖熊)。采用TNT软件包对11种祖先熊类和37个特征组成的数据进行不同条件(non-additive,additive等)下全搜索(Implicit Enumeration),并采用自引导法(bootstrapping)进行可信度评价。我们从基于部分特征加积(partially additive)条件下所得出8个最简约树中选取树5作为最可信简约树。该树表明,熊科从渐新世-早中新世的豺熊类(hemicyonids)分出后产生了两类基干类型,Ballusia elmensis和B.orientalis。后者稍更进步,可能为一特异支。此后产生了两大次支:一支向印度熊(可能还有郊熊)+大熊猫演化;另一支则由中-晚中新世的祖熊(Ursavus)和此后由某类祖熊所产生的现生熊类(不包括大熊猫)组成。从现有的化石判断,新建戴氏祖熊是与现生熊类在形态上最为接近的祖先类型,但戴氏祖熊具有某些自近裔性状,可能为一早期旁支。     

重庆巫山更新世反刍类臼齿的新类型及伴生的鹿化石(英文)

新月形颊齿是反刍类的鉴定特征之一,而反刍类的上臼齿通常由4个新月形主尖组成。2008年在重庆市巫山县庙宇镇新城村堰头溪地点的一建筑项目中从黏土质地基中挖掘出一件带有上颊齿的反刍类上颌骨残段,标本上的上臼齿由5个新月形主尖组成。伴生的其他动物有更新世麂属未定种(Muntiacus sp.)和黑鹿(Cervus(Rusa) unicolor)。形态学研究显示堰头溪标本的上臼齿代表一种新的新月形上臼齿类型,它不同于见于部分胼足类(tylopods)的5尖型上臼齿,例如古近纪的石炭兽类和xiphodontids以及分布于渐新世和中新世的真兽类。堰头溪标本上臼齿中的第五个主尖被诠释为原尖基部舌侧的齿带过度发育而成,与胼足类的舌侧主尖非同源关系。堰头溪标本代表一个新的种类,其分类位置暂定为麂亚科的麂属,即黄氏麂Muntiacus?huangi sp.nov.。     

Heating of a Local Region of a Branching Streamer as a Starting Point of a Space Leader and a Negative-Leader Step

Plasma Physics Reports - Localized plasma formations called space leaders are observed in streamer coronas of negative leaders of long laboratory sparks. The main leader completes a step when the...     

Geminiviruses: a tale of a plasmid becoming a virus

Background  

Geminiviruses (family Geminiviridae) are small single-stranded (ss) DNA viruses infecting plants. Their virion morphology is unique in the known viral world – two incomplete T = 1 icosahedra are joined together to form twinned particles. Geminiviruses utilize a rolling-circle mode to replicate their genomes. A limited sequence similarity between the three conserved motifs of the rolling-circle replication initiation proteins (RCR Reps) of geminiviruses and plasmids of Gram-positive bacteria allowed Koonin and Ilyina to propose that geminiviruses descend from bacterial replicons.     

Mechanisms of coexistence of a bacteria and a bacteriophage in a spatially homogeneous environment

When bacteriophage are added to laboratory bacteria populations, bacteria mutants that are resistant to the phage quickly dominate the population. The phage will only persist in the long‐term if there are sufficient bacteria in the population that show susceptibility to the phage. We investigated the mechanisms allowing for coexistence by adding the virulent bacteriophage φ6 to cultures of the bacterium Pseudomonas syringae pv. phaseolicola in a spatially homogeneous environment. We saw large differences between replicate cultures, in particular when one or both of the species persisted. These differences can be explained by variation in the timing of the appearance of various resistant phenotypes in the bacteria populations before the phage were added, which determines their relative frequencies within the populations. Although these resistant phenotypes have similar fitnesses in the presence and in the absence of the phage, they have a profound effect on the persistence of the phage. Our results give a clearer understanding of the ecological mechanisms that lead to the coexistence of bacteria and virulent phage in environments where there are no spatial refuges available to the bacteria population.     

Effects of a disease affecting a predator on the dynamics of a predator-prey system

We study the effects of a disease affecting a predator on the dynamics of a predator-prey system. We couple an SIRS model applied to the predator population, to a Lotka-Volterra model. The SIRS model describes the spread of the disease in a predator population subdivided into susceptible, infected and removed individuals. The Lotka-Volterra model describes the predator-prey interactions. We consider two time scales, a fast one for the disease and a comparatively slow one for predator-prey interactions and for predator mortality. We use the classical “aggregation method” in order to obtain a reduced equivalent model. We show that there are two possible asymptotic behaviors: either the predator population dies out and the prey tends to its carrying capacity, or the predator and prey coexist. In this latter case, the predator population tends either to a “disease-free” or to a “disease-endemic” state. Moreover, the total predator density in the disease-endemic state is greater than the predator density in the “disease-free” equilibrium (DFE).     

Characterization of a protease of a feather-degrading Microbacterium species

AIMS: To characterize a new feather-degrading bacterium. METHODS AND RESULTS: The strain kr10 producing a high keratinolytic activity when cultured on native feather broth was identified as Microbacterium sp., based on phenotypical characteristics and 16S rDNA sequence. The bacterium presented optimum growth and feather-degrading activity at pH 7.0 and 30 degrees C. Complete feather degradation was achieved during cultivation. The keratinase was partially purified by gel filtration chromatography. It was optimally active at pH 7.0 and 55 degrees C. The enzyme was inhibited by 1,10-phenanthroline, EDTA, p-chloromercuribenzoic acid, 2-mercaptoethanol and metal ions like Hg(2+), Cu(2+) and Zn(2+). SIGNIFICANCE AND IMPACT OF THE STUDY: A new Microbacterium sp. strain was characterized presenting high feather-degrading activity, which appears to be associated to a metalloprotease-type keratinase. This micro-organism has enormous potential for use in biotechnological processes involving keratin hydrolysis.     

Facile synthesis of a D-galactono-1,6-lactone derivative, a precursor of a copolyester

2,3,4,6-Tetra-O-methyl-d-galactonic acid (5) was readily prepared from d-galactono-1,4-lactone (1) in 47% yield. The sequence involves tritylation of HO-6 of 1, followed by O-permethylation and deprotection. Lactonization of 5 led to the per-O-methyl-d-galactono-1,6-lactone, which was copolymerized with epsilon-caprolactone by ring-opening polymerization catalyzed by scandium triflate. The incorporation of the sugar comonomer into the polyester chain was about 10%.     

Glycan expression as a tool for a deeper understanding of a reproductive gland in a skate of economic importance

Atlantoraja platana is an oviparous skate endemic to the south-west Atlantic Ocean, and is one of the skate species most exploited by local industrial bottom trawl fisheries. Oviparous elasmobranchs encapsulate their eggs in complex egg cases produced by the oviductal gland (OG). This organ is exclusively present in these fishes and comprises four distinct zones: club, baffle, papillary and terminal. The relative size and structural complexity of these zones correlate with mode of reproduction. Glycans are known to play major roles in reproduction so their distribution in each zone of the OG could explain the functional multiplicity of the gland in skates, but this topic has not been previously investigated. In this study, morphological, histochemical and lectin-histochemical analysis revealed various novel aspects of A. platana's OG. The club, papillary and terminal zones positively stained for periodic acid Schiff's reagent (PAS) and Alcian Blue (AB), indicating the presence of neutral and acid mucopolysaccharides. However, the buffle zone was negative for PAS and AB stains, but was positive for all the lectins used. Each zone of the OG had a characteristic pattern of glycan expression. Finally, we confirmed the presence of sperm but not sperm storage. This is the first lectin-histochemical study of the OG in chondrichtyan fish and it has proven to be an important tool to understand some of the mechanisms of fertility and reproductive success in economic important species such as A. platana.