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 78 毫秒
1.
本文记述湖北宜昌地区奥陶纪大湾组下部的一个三叶虫新种Ovalocephalus eoprimitivus sp.nov.,主要特征是头鞍缺失前颈环横沟。Ovalocephalus Koroleva为泛冈瓦纳的标志分子,在中国奥陶系分布极为广泛。这一新种的时代为弗洛期一大坪期,系该属目前所知地层层位最低的分子。  相似文献   

2.
前言早寒武世海绵在文献中虽屡有报道(Rigby, 1976, 1986),但多为分散式保存的骨针,关于海绵骨骼整体化石的报道则极鲜见(Walcott,1886, 1889; Rigby, 1987)。云南澄江是世界上迄今所发现的保存大量完整海绵骨骼化石和层位最低的唯一产地。澄江海绵化石群的研究为重建海绵类早期历史提供了新的较可靠的科学依据。长期以来人们根据早寒武世地层中所发现的大量海绵骨针均为四射类型的事实,推测这一时期的海绵分异度低,主要由六射海绵少数分子所组成,普通海绵极稀少,还未得到发展(Rigby,1976,1986)。澄江海绵化石群的研究所得出的结论与以上的推测恰恰相反,实际上,早寒武世筇竹寺期的海绵在演化上已达到了一个新的高度,普通海绵已高度分异并成为海绵类中最主要的优势生物类型。在分异度、物种结构、骨骼结构方式和复杂程度等方面均表现了筇竹寺期海绵动物群与中寒武世布尔吉斯海绵动物群具有惊人的相似性;这些相似性表明,海绵动物在早寒武世早期(筇竹寺期)已达到演化上的第一高峰,在其后筇竹寺期到布尔吉斯期将近3千万年的地质历程中处于缓慢的渐进式进化过程。  相似文献   

3.
前言早寒武世海绵在文献中虽屡有报道(Rigby, 1976, 1986),但多为分散式保存的骨针,关于海绵骨骼整体化石的报道则极鲜见(Walcott,1886, 1889; Rigby, 1987)。云南澄江是世界上迄今所发现的保存大量完整海绵骨骼化石和层位最低的唯一产地。澄江海绵化石群的研究为重建海绵类早期历史提供了新的较可靠的科学依据。长期以来人们根据早寒武世地层中所发现的大量海绵骨针均为四射类型的事实,推测这一时期的海绵分异度低,主要由六射海绵少数分子所组成,普通海绵极稀少,还未得到发展(Rigby,1976,1986)。澄江海绵化石群的研究所得出的结论与以上的推测恰恰相反,实际上,早寒武世筇竹寺期的海绵在演化上已达到了一个新的高度,普通海绵已高度分异并成为海绵类中最主要的优势生物类型。在分异度、物种结构、骨骼结构方式和复杂程度等方面均表现了筇竹寺期海绵动物群与中寒武世布尔吉斯海绵动物群具有惊人的相似性;这些相似性表明,海绵动物在早寒武世早期(筇竹寺期)已达到演化上的第一高峰,在其后筇竹寺期到布尔吉斯期将近3千万年的地质历程中处于缓慢的渐进式进化过程。  相似文献   

4.
本文用Hha I DNA甲基化酶为工具酶,制备了不同甲基化水平的Micrococcus IuteusDNA,再用Sephadex G-100凝胶过滤将甲基化了的M.L.DNA分离出来.以园二色差光谱和紫外差光谱等手段检测了不同甲基化水平给M.L.DNA大分子造成的构象变化:随着DNA甲基化水平的的升高,其CD差光谱的值,及紫外差光谱的值均呈增加趋势.这说明DNA大分子的甲基化,使其分子在溶液中变得更为缩拢,而这种缩拢的程度与DNA大分子的甲基化水平呈正相关.  相似文献   

5.
甲基化作用对M.L.DMA大分子构象的影响   总被引:1,自引:0,他引:1  
本文用Hha I DNA甲基化酶为工具酶,制备了不同甲基化水平的Micrococcus IuteusDNA,再用Sephadex G-100凝胶过滤将甲基化了的M.L.DNA分离出来.以园二色差光谱和紫外差光谱等手段检测了不同甲基化水平给M.L.DNA大分子造成的构象变化:随着DNA甲基化水平的的升高,其CD差光谱的值,及紫外差光谱的值均呈增加趋势.这说明DNA大分子的甲基化,使其分子在溶液中变得更为缩拢,而这种缩拢的程度与DNA大分子的甲基化水平呈正相关.  相似文献   

6.
本文基于核糖体SSU rDNA序列对石耳科Umbilicariaceae的系统地位进行了研究.将所获得的石耳科地衣中6个种的SSU rDNA序列与GenBank中其它地衣型及非地衣型真菌的相关序列进行比对用于系统发育研究.结果表明长期以来系统地位不够明确而暂时被置于茶渍目Lecanorales的石耳科不能被包括在茶渍目中,分子数据支持成立石耳目Umbilicariales.基于分子数据并结合形态学和解剖学特征描述了新目Umbilicariales J.C. Wei & Q.M. Zhou(Lecanoromycetes,Ascomycota).  相似文献   

7.
本文基于核糖体SSU rDNA序列对石耳科Umbilicariaceae的系统地位进行了研究.将所获得的石耳科地衣中6个种的SSU rDNA序列与GenBank中其它地衣型及非地衣型真菌的相关序列进行比对用于系统发育研究.结果表明长期以来系统地位不够明确而暂时被置于茶渍目Lecanorales的石耳科不能被包括在茶渍目中,分子数据支持成立石耳目Umbilicariales.基于分子数据并结合形态学和解剖学特征描述了新目Umbilicariales J.C. Wei & Q.M. Zhou(Lecanoromycetes,Ascomycota).  相似文献   

8.
据Federal Register(1982,47卷3期)报导,美国卫生研究院涉及重组DNA分子研究在准则指导下考虑如下两项活动: 一、Minnetonka股分有限公司(Minnesota)分子遗传学工作者请求允许克隆FMDV亚基因组片段,要求批准转移少于FMDV全基因组的75%组成E.coli k-12 cDNA的无性系(注:此病毒来自Plum岛动物疾病研究中心)和批准在P_1牵制条件下用这些无性  相似文献   

9.
复活分子是指地层记录中一度消失、后来复现且未发生明显变化的特殊分类单元。本文将复活分子区分为狭义(穿越灭绝事件)和广义(平常时期)的两类;并认为不同型式灭绝事件后的复活分子存在差异,表明其与灭绝强度有关。本文再次讨论复活分子的不同概念及其意义,并对避难所提出新的认识,强调复活分子的实质是灭绝期缩减居群大小与分布的极端稀疏分类单元,识别其生物因素尤为重要。以华南奥陶-志留纪交界期的华夏正形贝腕足动物群的一个采样点为例,说明稀疏种对多样性的贡献颇为关键,只有依靠大量的采样与深入的系统古生物研究,才能识别;探索和发现复活分子的关键在于采样和系统学研究的深入程度;建议应更加客观地认识复活分子的宏演化意义。  相似文献   

10.
复活分子是指地层记录中一度消失、后来复现且未发生明显变化的特殊分类单元。本文将复活分子区分为狭义(穿越灭绝事件)和广义(平常时期)的两类;并认为不同型式灭绝事件后的复活分子存在差异,表明其与灭绝强度有关。本文再次讨论复活分子的不同概念及其意义,并对避难所提出新的认识,强调复活分子的实质是灭绝期缩减居群大小与分布的极端稀疏分类单元,识别其生物因素尤为重要。以华南奥陶-志留纪交界期的华夏正形贝腕足动物群的一个采样点为例,说明稀疏种对多样性的贡献颇为关键,只有依靠大量的采样与深入的系统古生物研究,才能识别;探索和发现复活分子的关键在于采样和系统学研究的深入程度;建议应更加客观地认识复活分子的宏演化意义。  相似文献   

11.
Two species of Phycodrys, Phycodrys quercifolia (Bory) Skottsberg and Phycodrys profunda E.Y.Dawson were previously recorded from New Zealand. However, an examination of Phycodrys collections from the New Zealand region showed that all were morphologically different from P. quercifolia (Type locality: the Falkland Islands) and P. profunda (Type locality: CA, USA). RbcL sequence analyses established that the New Zealand Phycodrys species formed a natural assemblage within the genus, consisting of three new species: P. novae-zelandiae sp. nov., P. franiae sp. nov. and P. adamsiae sp. nov. Phycodrys novae-zelandiae is the largest of the three, up to 20 cm in height, with a distinct midrib and multicellular, opposite to subopposite lateral macroscopic veins. It has entirely monostromatic blades except near the midrib and veins, and its procarp contains a three-celled sterile group one (st1) and a one-celled sterile group two (st2). Phycodrys franiae was previously treated as a cryptic species among herbarium collections of P. ‘quercifolia’. It is smaller (4–11 cm high) with weakly developed midribs and veins, the blade is tristromatic throughout, except at the growing margins, and the procarp consists of a four-celled st1 and a two–three-celled st2. Phycodrys adamsiae, previously reported as P. profunda, is a small decumbent or prostrate plant, 1–8 cm long, with a midrib and inconspicuous lateral veins. The blades are tristromatic with serrated margins, two–four-celled surface spines and multicellular marginal holdfasts that differ from those of Californian specimens. The tetrasporangia are borne on marginal bladelets. Phylogenetic analyses place the New Zealand species in a separate group that is distantly removed from most other Phycodrys species.  相似文献   

12.
Nine strains of three novel anamorphic yeast species were obtained from samples collected in Thailand including six strains (RV96, RV152, R14, RS9, RS58 and EA1) obtained from estuarine waters collected from two mangrove forests, one strain (ST84) from insect frass and two strains (SR16 and UB13) from forest soils. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, and the sequence analysis of the D1/D2 domain of the large subunit rRNA gene, the nine strains were found to represent three novel Candida species in the Saturnispora clade. Five strains (RV96, RV152, R14, RS9 and RS58) were assigned as a single novel species, which was named Candida sanitii sp. nov. The type strain is RV152T (BCC 25967T=NBRC 103864T=CBS 10864T). Strain EA1 was named as Candida suwanaritii sp. nov. The type strain is EA1T (BCC 29900T=NBRC 104877T=CBS 11021T). Three strains (ST84, SR16 and UB13) represented another novel species, for which Candida sekii sp. nov. is proposed. The type strain is ST84T (BCC 8320T=NBRC 105671T=CBS 10931T).  相似文献   

13.
The flies of the genus Dicranosepsis from Vietnam were investigated and classified taxonomically. Six new species (D. longa sp. nov., D. kurahashii sp. nov., D. monoseta sp. nov., D. sinuosa sp. nov., D. barbata sp. nov., and D. vietnamensis sp. nov.) are described and illustrated. Dicranosepsis is redefined and a revised key to the species is also provided.  相似文献   

14.
Strains XZ-46A, XZ-105, XZ-129 and XZ-281T isolated from the oral cavities of healthy Tibetan volunteers were revealed to represent two novel ascomycetous yeast species by molecular taxonomic characterizations. Strain XZ-281T was most closely related to Candida humilis , but differed from the type strain of the species by eight (1.2%) substitutions in the 26S rRNA gene D1/D2 domain and by >100 (>20%) mismatches in the internal transcribed spacer (ITS) region. Strains XZ-46A, XZ-105 and XZ-129 had identical or similar D1/D2 and ITS sequences with each other and with strain 17YFT isolated from a leaf of an oak tree ( Quercus sp.). The closest relative of this group was Torulaspora microellipsoides . They differed from the type strain of the species by five (0.9%) substitutions in the D1/D2 domain and >70 (>15%) mismatches in the ITS region. A sexual state was observed in strain 17YFT, but not in the other four oral strains. An anamorphic name Candida pseudohumilis sp. nov. is proposed for strain XZ-281T (=AS 2.3956T=CBS 11404T) and a teleomorphic name Torulaspora quercuum sp. nov. is proposed for strain 17YFT (=AS 2.3768T=CBS 11403T) and the other three oral strains.  相似文献   

15.
16.
Cryptonemia specimens collected in Bermuda over the past two decades were analysed using gene sequences encoding the large subunit of the nuclear ribosomal DNA and the large subunit of RuBisCO as genetic markers to elucidate their phylogenetic positions. They were additionally subjected to morphological assessment and compared with historical collections from the islands. Six species are presently found in the flora including C. bermudensis comb. nov., based on Halymenia bermudensis, and the following five new species: C. abyssalis, C. antricola, C. atrocostalis, C. lacunicola and C. perparva. Of the eight species known in the western Atlantic flora prior to this study, none is found in Bermuda. Specimens reported in the islands in the 1900s attributed to C. crenulata and C. luxurians are representative of the new species, C. antricola and C. atrocostalis, respectively.  相似文献   

17.
系统描述湖北宜昌和秭归新滩晚奥陶世庙坡组三叶虫动物群中的3科6属6种。根据化石保存状态,挤压变形以及个体发育特征,对前人所报道的产于同一层位的有并三叶虫的研究成果作了重新厘定。  相似文献   

18.
描述了采自长白山永青电站的蓝藻门新植物灰白伪枝藻(Scytonema cineraceum C.L.Zhou et Xiao, sp. nov.), 其原植体丛生,垫状,近半球形,灰褐色。蓝藻门新植物岩生蓝柄藻(Cyanostylon rupestris L .H.Lü et Xiao, sp. nov.),采自吉林省集安市五女峰,植物团块为较柔软的胶质小皮壳状堆积体,棕黄色或棕红色。  相似文献   

19.
吉林省蓝藻门两新种   总被引:1,自引:0,他引:1  
报道了采自吉林省的蓝藻门2个新种:具翼单歧藻Tolypothrix alata,脆弱真枝藻Stigonema fragile。  相似文献   

20.
Pihiella liagoraciphila gen. et sp. nov. (Rhodophyta) is described for a minute endo/epiphyte that is commonly associated with members of the Liagoraceae ( Nemaliales, Rhodophyta). Algae are discoid or subspherical and grow to a maximum diameter of 400 μm. Attachment is via isolated elongate rhizoids that penetrate into the loosely filamentous structure of the host or by a pad of several coalesced rhizoids where the host has a more cohesive cortex. Elongate surface hairs are common. Gametophytes are dioecious, the spermatangia arising on surface cells, and carpogonia with elongate trichogynes borne directly on undifferentiated surface supporting cells. Large sporangia form on stalk cells across the upper surface of the plants, these appearing to be either monosporangial or the result of fertilization of the carpogonia and equivalent to undivided zygotosporangia. Carposporophytes and tetrasporangia are unknown. 18S rRNA gene sequence analyses indicate that Pihiella constitutes a clade of long branch length most closely related to the Ahnfeltiales. The unique morphology and reproduction of Pihiella , combined with a substantial genetic divergence from the Ahnfeltiales, suggest that it is sufficiently distinct to warrant placement in a new family and order. We therefore describe the family Pihiellaceae and the order Pihiellales to accommodate the new genus.  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