首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
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。  相似文献   

2.
河南范县三叠纪轮藻   总被引:3,自引:1,他引:2  
本文记述的轮藻化石,采自河南范县地区三叠系钻孔岩样中,共3属10种,其中3新种,1未定种。中三叠统聊城组含轮藻化石2属7种,下三叠统和尚沟组产轮藻2属4种。这些轮藻化石的发现,为华北地区井下早第三纪沙河街组之下,二叠系石盒子群之上广泛发育厚达2000余米的红色砂泥岩地层的划分对比与地质时代的确定提供了宝贵的古生物依据。  相似文献   

3.
内蒙古银根-额济纳旗盆地白垩纪轮藻化石   总被引:5,自引:1,他引:4  
本文记述了内蒙古银根一额济纳旗盆地8口钻井的白垩纪轮藻化石,建立两个轮藻化石组合:Mesochara stipitata-Clypeator jiuquanensis-Flabellochara hebeiensis组合,分布于巴音戈壁组与苏红图组,地质时代为Barremian期;Aclistochara mundula-Mesochara voluta组合产于银根组,地质时代为Aptian-Albian期。  相似文献   

4.
中国现生轮藻研究现状   总被引:1,自引:0,他引:1  
中国是轮藻的主要产地,记有5属、152种、39变种,且半数以上为中国特有种、变种,其研究对世界轮藻研究意义重大。然而我国的相关研究起步晚,虽在20世纪的80年代进行了较为全面的资源调查,但其后的研究几乎处于停顿状态,尽管一些单位在轮藻生理、细胞学、多样性以及现生与化石轮藻研究的相关性等方面有着良好的研究苗头,却未能得到足够的重视,使我国现生轮藻研究大大落后于国际同行。积极寻求项目支持,打开现生轮藻研究新局面是我们的当务之急。  相似文献   

5.
山西垣曲盆地始新世轮藻植物群   总被引:2,自引:2,他引:0  
记述山西垣曲盆地河堤组任村至寨组里段轮藻化石,计11属,14种,2未定种,建立了一个地区性轮藻化石组合:Raskyellasinensis-Linyiecharadecorosa-Stephanocharaglobula组合,该组合位于中国早第三纪轮藻植物群序列中Obtusocharajianglingensis-Gyrogonaqianjiangica植物群的上部,轮藻植物群反映的地质时代始新世  相似文献   

6.
甘肃花海盆地截大板沟早白垩世轮藻化石   总被引:3,自引:1,他引:3  
详细研究了首次发现于甘肃花海盆地截大板沟下白垩统下沟组的轮藻化石,建立了Aclistochara huihuibaoensis-Peckisphera paragranulifera组合,重新厘定了中生代地层层序。根据轮藻化石的组合面貌及其在国内外分布的主要层位,认为原划归为中-上侏罗统,并含有丰富轮藻化石的这套地层应属下白垩统下沟组,其时代为早白垩世Barremian期。  相似文献   

7.
陕西三叠纪轮藻化石   总被引:4,自引:0,他引:4       下载免费PDF全文
本文描述了产自陕西耀县、铜川、韩城地区三叠系的轮藻化石3亚科、4属、6种,其中包括1新属和3新种。在切片研究中,发现了Stellatochara 的底塞,从而对长期来有所争论的该属标本的定向问题提供了可靠的依据。陕西三叠纪轮藻化石的记述是亚洲地区三叠纪轮藻类的首次报道。  相似文献   

8.
青海柴达木盆地第三纪轮藻化石   总被引:7,自引:1,他引:6       下载免费PDF全文
王水 《古生物学报》1961,(3):183-209
一、绪言近年来轮藻化石曾发现于我国许多地区的泥盆纪、侏罗纪、第三纪和第四纪地层中,其中以青海柴达木盆地的第三纪地层发现最多。本文所描述的就是青海柴达木盆地红三旱Ⅰ号、鄂博梁Ⅰ、Ⅱ、Ⅲ号及冷湖Ⅶ号5个地区第三纪地层所产的轮藻化石,计1科、4亚科、8属、42种、6亚种和1变种,其中包括27个新种和1个新变种。柴达木盆地轮藻化石的分布以盆地中心最为丰富,如鄂博梁Ⅱ号、Ⅲ号及冷湖Ⅶ  相似文献   

9.
斋桑盆地自晚白垩世以来即为淡水湖泊环境,其始新世至中新世湖相及湖边缘相沉积物产有丰富的轮藻化石。文中建立三个轮藻化石组合:(1)Harrisichara mitella—Peckisphaera zajsanica组合(中始新世早期);(2)Lychnothamnus formosus—Peckichara组合(中始新世晚期--渐新世早期);(3)Gyrogona aralica—sphaerochara clearus组合(中--晚渐新世)。斋桑盆地轮藻化石出现的最高层位为下中新统且化石稀少,推测系盆地环境日益干旱所致。  相似文献   

10.
二连盆地白音查干凹陷早白垩世轮藻化石及其时代意义   总被引:1,自引:1,他引:0  
本文首次报道二连盆地西部白音查干凹陷井下剖面轮藻化石3属5种,其中1新种,2未定种。根据轮藻化石的区域分布,证实含化石地层的时代为早白垩世。  相似文献   

11.
西藏台错晚第四纪轮藻类的新类型   总被引:1,自引:0,他引:1  
本文的研究材料来自西藏羌塘高原西部台错古湖一个3.69 m的天然剖面,其地层测年为32.6-4.5ka.从其156个样品中获取大量的轮藻类、介形类和腹足类及少量有孔虫等微体化石.据轮藻类藏卵器外形,顶部结构、螺旋细胞钙化式样等特征,该剖面的轮藻类应归属于轮藻科Characeae之轮藻属Chara.经研究得知,台错古湖在...  相似文献   

12.
Charophytes and otoliths from theCyrena Beds of the northern Alpine foreland (Hausham and Miesbach synclines, Upper Bavaria) have been studied. A very abundant charophyte flora comprising 12 species, includingStephanochara martinii n. sp., is described and figured. The moderately diverse otolith fauna is documented by tables and SEM-pictures. The studiedCyrena Beds can be dated biostratigraphically as early Chattian and correlated with theChara microcera Zone. The charophytes show strong paleobiogeographic relations to floras in the Mainz Basin/Upper Rhine Graben as well as to western Switzerland and southern France. The otolith fauna is strikingly different from late Chattian faunas of the western Paratethys. The paleoecology indicated by charophytes, otoliths and the accompanying fauna suggests short term variation including freshwater, brackish water and marine influenced environments.  相似文献   

13.
Receptor-like kinases (RLKs) play significant roles in mediating innate immunity and development of plants. The evolution of plant RLKs has been characterized by extensive variation in copy numbers and domain configurations. However, much remains unknown about the origin, evolution, and early diversification of plant RLKs. Here, we perform phylogenomic analyses of RLKs across plants (Archaeplastida), including embryophytes, charophytes, chlorophytes, prasinodermophytes, glaucophytes, and rhodophytes. We identify the presence of RLKs in all the streptophytes (land plants and charophytes), nine out of 18 chlorophytes, one prasinodermophyte, and one glaucophyte, but not in rhodophytes. Interestingly, the copy number of RLKs increased drastically in streptophytes after the split of the clade of Mesostigmatophyceae and Chlorokybophyceae and other streptophytes. Moreover, phylogenetic analyses suggest RLKs from charophytes form diverse distinct clusters, and are dispersed along the diversity of land plant RLKs, indicating that RLKs have extensively diversified in charophytes and charophyte RLKs seeded the major diversity of land plant RLKs. We identify at least 81 and 76 different kinase-associated domains for charophyte and land plant RLKs, 23 of which are shared, suggesting that RLKs might have evolved in a modular fashion through frequent domain gains or losses. We also detect signatures of positive selection for many charophyte RLK groups, indicating potential functions in host–microbe interaction. Taken together, our findings provide significant insights into the early evolution and diversification of plant RLKs and the ancient evolution of plant–microbe symbiosis.  相似文献   

14.
Charophytes are a highly endangered group of algae. In the Baltic Sea, the number of species, distribution area and biomass of charophytes have significantly decreased in recent decades. Although eutrophication triggers their initial decline, the mechanism of the final extinction of charophyte populations is not fully understood. An in situ experiment was performed to study the role of the mesoherbivores Idotea baltica, Gammarus oceanicus and Palaemon adspersus in the decline of charophytes in the north-eastern Baltic Sea. Invertebrate grazing showed a clear seasonality: grazing pressure was low in April, moderate in July, and high in October. Grazing on charophytes by P. adspersus was negligible, whereas I. baltica and G. oceanicus significantly reduced the biomass of charophytes in the field. Low photosynthetic activity (high decomposition rate) of the charophytes favoured grazing. The invertebrates studied preferred Chara tomentosa to C. connivens. Low consumption of C. connivens may reflect its non-native origin. The experiment suggests that, under moderately eutrophic conditions, grazers are not likely to control charophyte populations. However, grazers have the potential to eliminate charophytes in severely eutrophic systems under the stress of filamentous algae.Communicated by H.D. Franke  相似文献   

15.
欧洲东南部巴尔干轮藻植物由于其产地生境的差异及以镶嵌状分布的模式,具有较高的生物分异度,计有44种,归属于现生属Nitella(10),Tolypella(4),Nitellopsis(1),Lychnothamnus(1),Lamprothamnium(1) and Chara(27).巴尔干半岛产有4种土著类型Chara rohlenae,Chara ohridana,Chara corfuensis and Chara visianii.建立1新种Chara hydropitys.该地区轮藻植物分布不均衡,部分类型例如Chara strigosa,Chara kokeilii,Chara muscosa,Chara fragifera,Chara imperfecta,Lychnothamnus barbatus为稀有品种,仅在少数地点发现.巴尔干地区轮藻植物之丰富多彩远远超过已知的程度,有待于深入研究.  相似文献   

16.
西北地区潮水盆地侏罗系青土井群轮藻化石   总被引:2,自引:0,他引:2  
潮水盆地青土井群为一套含煤碎屑岩,在盆地东部潮参l井青土井群三段发育大量以Aclistochara占优势的轮藻化石群,其组合特征显示浓厚的晚侏罗世色彩。青土井群一、二段轮藻化石稀少,结合地层层序,推测其地质时代为早侏罗世。围岩沉积特征表明本井轮藻化石群为浅水生物群。  相似文献   

17.
In Tunisia, in the platform domain, the Aptian-Albian transition is associated with a major stratigraphic gap not precisely dated, which is related to the subaerial exposure of the Aptian Orbata platform. Locally, in central Tunisia (Jebel Kebar), this gap is substituted by the sedimentary records of the Kebar Formation. This formation provided a rich association of fossil charophytes, formed by Atopochara trivolvis trivolvis, Clavator harrisii zavialensis and Sphaerochara verticillata which allows attributing it to the late Aptian–early Albian interval (most probably early Albian). In addition, a new variety, Sphaerochara verticillata var. kebariensis, is described. The charophyte assemblage shows significant biogeographic affinities with a coeval flora found in the Iberian Peninsula. The Kebar Formation was previously regarded as exclusively nonmarine, but the presence of the assemblage of charophytes and associated ostracods described rather indicates a fluctuation between margino-littoral (lagoonal) and continental environments.  相似文献   

18.
The objective of this study was to determine the effects of UV-B radiation on charophycean algae under natural conditions, since charophytes enhance water transparency in freshwater systems and levels of UV-B radiation have increased by ozone depletion. Potential and actual UV-B effects were studied by combining a glasshouse experiment in which plants were exposed to various levels of UV-B radiation and field measurements in two freshwater systems dominated by charophytes in the Netherlands. The glasshouse experiment showed that charophytes were sensitive to UV-B radiation. UV-B radiation negatively affected growth, while it increased levels of DNA damage in Chara aspera. Moreover, the charophytes did not seem to develop UV-B screens to protect against UV-B radiation since no increase in UV-B absorbing compounds was found. At field conditions, both spectroradiometrical measurements and DNA dosimeters showed that UV-B radiation was attenuated quickly in both freshwater systems, indicating that UV-B does not reach the submerged charophyte vegetation. However, specific conditions, like fluctuating water tables, may result in UV-B exposure to charophytes for certain periods annually.  相似文献   

19.
To gain insights into the phylogeny of charophytes and into their relationships with other green algae and bryophytes, we analyzed the chloroplast small and large subunit rRNA sequences of charophytes belonging to five orders (Charales, Coleochaetales, Desmidiales, Klebsormidiales, and Zygnematales), of chlorophytes from the four remaining classes of green algae, and of bryophytes representing the three classes reported in this group of land plants. We also probed the gene organization and intron content of the chloroplast rDNA operon in charophytes and bryophytes. The organization of this operon proved to be highly conserved, except in members of the Desmidiales and Zygnematales. Homologous group II introns were identified in the trnA(UGC) gene of all charophyte groups examined and in the trnI(GAU) gene of charophytes from all orders except the Desmidiales and Zygnematales. Phylogenetic analyses of concatenated rDNA sequences consistently placed the prasinophyte Mesostigma viride Lauterborn at the base of the Streptophyta and Chlorophyta, although alternative topologies positioning Mesostigma within the Streptophyta could not be rejected. A sister group relationship was unambiguously established between Chaetosphaeridium globosum (Nordstedt) Klebahn and members of the Coleochaetales. The Charales, Coleochaetales, Desmidiales, and Zygnematales were found to be monophyletic, and a sister group relationship was observed for the Desmidiales and Zygnematales. Although our analyses failed to resolve the branching order of the Coleochaetales, Charales, Desmidiales/Zygnematales, and bryophytes, they revealed that the problematic charophyte taxon Entransia fimbriata Hughes strongly clusters with Klebsormidium flaccidum (Kützing) Silva, Mattox et Blackwell to form a basal lineage relative to the other charophyte orders examined.  相似文献   

20.
吐鲁番盆地连木沁剖面齐古组轮藻化石   总被引:1,自引:0,他引:1  
吐鲁番盆地连木沁剖面侏罗系齐古组的轮藻化石在早年资料中未见提及。后期曾有不同单位多人次对此剖面进行观察实测,除偶有提起见到轮藻外,亦均未见描述报道,本文首次正式报道了齐古组的轮藻化石,为吐鲁番盆地齐古组与广布于新疆各地区的齐古组进行横向对比提供了这类化石依据。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号