吉中地区晚古生代腕足动物古生物地理与环境的协同演化*

吉中地区发育了普里道利期—洛霍考夫期Retziella、杜内期通气沟组以及空谷期—沃德期哲斯等腕足动物群。前两者属于"暖水"动物群、后者属于"凉水"动物群。同时参考珊瑚和等动物群分析,说明吉中地区从普里道利期至阿瑟尔期发育"暖水"动物群,从空谷期到沃德期发育"凉水"动物群。"凉、暖"转换是以寿山沟组的Monodiexodina动物群为代表,发生在萨克马尔期。"凉、暖"水动物群的发育及其转换是构造古地理与气候变化双重因素导致的结果。晚志留世—早泥盆世,西伯利亚板块、哈萨克斯坦板块、佳-蒙地块均位于中—低纬度带。吉中地区晚志留世—早泥盆世(乃至中泥盆世)腕足动物群属于"暖水"动物群,古生物地理区划属于中-澳生物地理区。石炭纪,东欧板块东北缘、哈萨克斯坦板块大部分地区、佳-蒙地块南缘属于特提斯洋北缘构造域,发育了特提斯洋北缘腕足动物群,形成了特提斯北缘生物地理区,吉中地区腕足动物群属于这一生物地理区。空谷期—沃德期凉水型哲斯腕足动物群的形成是由于佳-蒙地块西端与塔里木板块以及华北板块西端拼合,形成了西拉木伦洋构造域,以及此时期全球降温事件导致的结果。古生物地理、构造古地理以及古气候之间的协同演化关系表明吉中地区晚古生代地层应属于佳-蒙地块南缘的大陆边缘沉积。     

西藏普兰县姜叶玛地区中二叠统西兰塔组中的有孔虫及其地质意义

西藏雅鲁藏布江缝合带蛇绿混杂岩中混杂着大小不一的二叠纪灰岩块体,它的来源一直颇有争议,这些灰岩块体中动物群的古生物地理面貌是判断其来源的重要手段。姜叶玛灰岩体是位于西藏普兰县境内混杂在中生代蛇绿混杂岩中的一个大型二叠纪灰岩块体。其中,中二叠世西兰塔组中含有丰富的非?有孔虫化石,它们主要由Neodiscus,Climacammina,Pachyphloia和Lysites组成,伴生有Dagmarita,Deckerella,Globivalvulina,Neoendothyra,Lasiodiscus,Lasiotrochus,Tetrataxis,Geinitzina,Ichthyofrondina,Nodosaria,Nodosinelloides,Agathammina,Septoagathammina和Shanita,时代相当于中二叠世Capitanian期。古生物地理上,Lysites和Shanita的出现表明这个动物群属于基墨里生物区,它们从古生物地理上以及生物多样性上和印度板块北缘的巴基斯坦盐岭地区以及藏南喜马拉雅区的同时代动物群有显著差别。结合前期?类动物群古生物地理的研究,姜叶玛灰岩块体很可能位于拉萨地块与喜马拉雅之间的新特提斯洋海山上,与两个地块之间都有一定的隔离。这也说明新特提斯打开的时间早于中二叠世。     

甘肃举办古生物夏令营

今年夏天,甘肃古生物学会组织了由兰州市十九所中学、二十二位生物教师参加的古生物夏令营。地点选在中生代与晚古生代地层发育,动植物化石丰富的甘肃靖远煤矿。通过两天的野外活动,生物教师们初步掌握了地层古生物野外工作方法,采集了蕨类、石松、苏铁、苔藓虫、珊瑚和海百合类等十几个门类六百多块化石,它们将是中学生     

中国石炭-二叠纪放射虫化石带及古生物地理学意义

中国广西钦州地区和云南西部昌宁—孟连地区的层状硅质岩地层中发育丰富的石炭—二叠纪放射虫生物群,据此建立了22个连续的放射虫化石带。从晚石炭世至晚二叠世长兴期,日本西南区出现的Pseudoalbaillella nodosa带至Neoalbaillella optima带共15个放射虫生物带可与中国同期发育的17个放射虫生物带对比,代表泛大洋(Panthalassa)沉积的部分日本地体和代表古特提斯洋(Palaeo-Tethys)沉积的中国部分构造单元,无论在放射虫生物类群组分还是在化石生物带构成方面都非常相似。晚石炭世—二叠纪放射虫生物地层学资料证实,该时期地球上的两个大洋(泛大洋和特提斯洋)没有明显的分化,可能属于同一大洋体系———古特提斯洋。     

滇西保山地区石炭纪、二叠纪古动物地理演化

探讨滇西保山地块晚古生代Ｔｉｎｇ类、有孔虫、珊瑚、牙形刺、腕足类等动物群的古生物地理属性,根据牙形刺和Ｔｉｎｇ类化石,确定长期争论的丁家寨组的时代为Ａｒｔｉｎｓｋｉａｎ期,小型单体珊瑚Ｃｙａｔｈａｘｏｎｉａ动物群可出现在从早石炭世到二叠纪的多种沉积环境中,不一定指示冷水冈瓦纳型。根据沉积特征及对环境特别敏感的珊瑚和Ｔｉｎｇ类动物群的分布特点,结合全球构造事件,恢复保山地块的古地理演化模式。早石炭世     

中国晚古生代轮藻化石组合

本文综述了数十年来中国晚古生代轮藻化石研究成果。与全球其它地区相比较,中国古生代轮藻化石较为丰富,可归纳为九个轮藻化石组合及三个轮藻化石层位。依据轮藻植物组成特点、演化特征以及伴生其它门类化石,论证各组合的地质时代,其中两个组合地质时代相同,属于不同的生物地理区系。     

论中国北方晚二叠世混生植物群的区系划分

自昆仑山—阿尔金山—祁连山—秦岭—大别山一线以北的中国北方地区,二叠纪时大约由准噶尔地块、塔里木地块、中朝板块、佳蒙地块等几个主要陆块和一些小的地块(微板块)组成。在系统整理这些地区晚二叠世植物属种的基础上,根据植物群属种的植物学特征及植物地理属性,将中国北方晚二叠世混生植物地理区划分为6个植物地理省,即:1)准噶尔–北塔里木安加拉–华夏混生植物地理省;2)北山–巴丹吉林安加拉–华夏混生植物地理省;3)兴蒙(东北地区)安加拉–华夏混生植物地理省;4)南塔里木安加拉–欧美混生植物地理省;5)祁连–阿拉善华夏–安加拉混生植物地理省;6)华北欧美–华夏–安加拉混生植物地理省。基于各地块在晚古生代各时期植物群的演替和植物区系性质的变迁,结合古地磁资料,简述了各地块在石炭纪—二叠纪时,在古特提斯洋和古亚洲洋中逐渐由低纬度热带亚热带雨林气候区向北半球高纬度温带干旱气候区的漂移和碰撞过程;并认为晚二叠世混生植物群形成的主要原因是各陆块相互间的迁移和拼接,中、晚二叠世形成的联合大陆(Pangaea)给各陆块上植物群的互相交融、侵入提供了良好条件。这种时空关系的改变,导致植物生态系统的改变,不但造成来自不同植物地理区植物的混生,而且产生了不少新的物种和丰富的土著分子。     

滇西南耿马弄巴剖面的晚古生代放射虫动物群

滇西南耿马弄巴剖面的硅质岩层中,存在大量放射虫化石,计有12属28种,时代跨越晚古生代,可建立两个组合和三个化石带:晚泥盆世Entactinia-Entactinosphaera组合;早石炭世杜内期中期Albaillellaparadoxa带,杜内期晚期—维宪期早期Albaillellaindensis带,维宪期中期Albaillellacartalla带;晚二叠世Entactiniaitsu-kaichiensis组合。弄巴剖面是由7个主要地层断片组成的断片型地层体,放射虫的研究为地层断片的时代归属问题提供了准确的微体古生物证据。     

古生代生物地理与古地理国际学术讨论会在英国牛津举行

由伦敦地质学会、古生物协会和国际岩石圈委员会2B工作组联合发起的“古生代生物地理与古地理学术讨论会”(Palaeozoic Biogeography and Palaeogeography Symposium)于1988年8月14～19日在英国著名的大学城牛津(Oxford)召开。参加这次会议的有来自世界上11个国家约85名专家学者。其中以美国参加的人数最多,占总人数的50％以上。而东道主英国只有17人参加,仅占20％左右。中国有3位古生物学家应邀出席了这次盛会,他们是中国科学院南京地质古生物研究所的张璐瑾和廖卫华以及地质矿产部地质研究所的侯鸿飞。此外目前在英国进修古地     

中国泥盆纪珊瑚的生物地理及其群落生态

中国泥盆纪可识别出６个珊瑚生物地理区：南天山区、古特提斯区、华南区、华北北缘区、准噶尔－兴安区和保山区。其中,前４４个区均处于当时赤道两侧的低纬度地区,属于老世界大区;而后２个区则可能分别位于北温带和南温带区域内,不在老世界大区范围内。中国泥盆纪珊瑚群大多数都是生活在温暖浅海近南栅上富氧透光带中的群落,其分异度,丰度和密度各有不同,大致属于海浪底栖生物组合ＢＡ３－ＢＡ４;但也有的生活在远岸大陆斜坡     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.