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1.
The diversity of Cretaceous gymnosperms from the Alchan Depression in northwestern Primorye is discussed. The pike of gymnosperm diversity is restricted to the middle of the Late Albian, and a sharp decline took place in the terminal Albian. A new species, Dictyozamites serafimae sp. nov., is described.  相似文献   

2.
Summary Reef facies, reef types and their biotic associations in the Maiella platform margin (central Italy) provide qualitative evidence for a significant reef decline across the Cretaceous/Tertiary (K/T) boundary, and indicate two phases of reef recovery during the Paleocene. Rudists dominated the reef community until the latest Cretaceous. A significant sea-level fall around the time of the K/T boundary is documented by a truncation surface associated with emersion. During sea-level highstands in the Danian to Early Thanetian and, more extensively, during the Late Thanetian, coral-algal patch-reefs grew along the platform margin and top. Already in the Danian to Early Thanetian, the reef communities were more diverse and the constructional types more evolved than previously known from this time. Differences between the Danian to Early Thanetian coral association, the Late Thanetian association, and Late Cretaceous coral faunas may have ecological or evolutionary causes. Repeated emergence produced a complex diagenetic history in the Danian to Lower Thanetian limestones. All Paleocene reefs were displaced by gravitative redeposition. Coral-algal reefs are less important in the Early to mid Eocene, when alveolinid foraminifera dominated on the Maiella shelf. Reefs on the Maiella platform diversified and attained large sizes in the Late Eocene to Early Oligocene, as known from other Mediterranean platforms. The external controls on the Late Cretaceous to Oligocene evolution and demise of reef communities that are most easily demonstrated with our data are sealevel fluctuations and climate change. We propose that the change in reef biota and reef types across the K/T boundary and during the Early Tertiary were important causes of the parallel changes in platform growth style.  相似文献   

3.
A molecular clock based on ITS sequence data from the lichen genera Biatora and Phyllopsora is calibrated with the help of paleoclimatic data and evidence of forest history. The clock indicates that diversification within Biatora started as early as in the Late Cretaceous and took place during periods of climatic cooling, when new types of forest evolved and spread in the Northern Hemisphere. Arctic-alpine species of the genus appear to be of considerable age, dating back to the Late Eocene-Oligocene climatic cooling. By using calibrated phylogenies of epiphytic lichens it may become possible to date many paleoenvironmental events, for which little fossil evidence exists.  相似文献   

4.
Oxygen isotope analyses of Tertiary and Cretaceous planktic foraminifera indicate that species have been stratified with respect to depth in the water column at least since Albian time. There is a relationship between morphology and depth habitat. Species with globigerine morphology have consistently occupied shallower depths than have species with globorotalid morphology. Biserially arranged species occupied both shallow and deep levels in the water column. On the average, it appears that ancient species with shallow habitats have been more susceptible to dissolution and have been preserved less well than species dwelling in deeper habitats. This relationship is similar to that observed for Recent planktic foraminifera. Comparison of carbon isotope ratios of adult and juvenile forms indicates that either the source of the carbon found in the shell or the carbon isotopic fractionations which occur during calcite secretion change during the development of individual foraminifera. The carbon isotopic ratios do not provide a reliable means for reconstructing the depth habitats of ancient species. Temperature-depth profiles for tropical Tertiary oceans have been reconstructed from the isotopic temperatures of planktic and benthic foraminifera. The vertical thermal structure of Oligocene oceans resembled that of modern oceans most closely. Those of Paleocene and Maastrichtian times differed most from that of modern oceans.  相似文献   

5.
Two iron-enriched weathered profiles, both widely distributed in the Eromanga and Surat Basins of Queensland, have been investigated palaeomanetically. Normal and reversed polarities have been obtained from each profile, indicating that the weathering events spanned at least one reversal of the geomagnetic field. The minimum duration of weathering for the older of the two profiles is estimated as 10,000 years. The palaeomagnetic directions when compared with the Late Cretaceous and Cainozoic apparent polar wander curve for Australia give a Maastrichtian to Early Eocene age for one profile and an approximately Late Oligocene age for the other. These ages are consistent with times of high palaeotemperature indicated by oxygen isotope analysis of marine fossils of the Southeast Indian Ocean. The pole position for the younger profile is not significantly different from pole positions obtained in previous palaeomagnetic investigations of weathered rocks in Western Australia, South Australia and the Northern Territory, supporting the long-held view of a mid-Tertiary continent-wide weathering event in Australia.  相似文献   

6.
7.
The global warming trend of the latest Oligocene was interrupted by several cooling events associated with Antarctic glaciations. These cooling events affected surface water productivity and plankton assemblages. Well-preserved radiolarians were obtained from upper Oligocene to lower Miocene sediments at Ocean Drilling Program (ODP) Leg 199 Sites 1218 and 1219 in the equatorial Pacific, and 110 radiolarian species were identified.Four episodes of significant radiolarian faunal changes were identified: middle late Oligocene (27.5 to 27.3 Ma), latest Oligocene (24.4 Ma), earliest Miocene (23.3 Ma), and middle early Miocene (21.6 Ma). These four episodes approximately coincide with increases and decreases of biogenic silica accumulation rates and increases in δ18O values coded as “Oi” and “Mi” events. These data indicate that Antarctic glaciations were associated with change of siliceous sedimentation patterns and faunal changes in the equatorial Pacific.Radiolarian fauna was divided into three assemblages based on variations in radiolarian productivity, species richness and the composition of dominant species: a late Oligocene assemblage (27.6 to 24.4 Ma), a transitional assemblage (24.4 to 23.3 Ma) and an early Miocene assemblage (23.3 to 21.2 Ma). The late Oligocene assemblage is characterized by relatively high productivity, low species richness and four dominant species of Tholospyris anthophora, Stichocorys subligata, Lophocyrtis nomas and Lithelius spp. The transitional assemblage represents relatively low values of productivity and species richness, and consists of three dominant species of T. anthophora, S. subligata and L. nomas. The characteristics of the early Miocene assemblage are relatively low productivity, but high species richness. The two dominant species present in this assemblage are T. anthophora and Cyrtocapsella tetrapera. The most significant faunal turnover of radiolarians is marked at the boundary between the transitional/early Miocene assemblages.We also reviewed changes in other microfossil assemblages in the low latitudes during the late Oligocene through early Miocene. The microfossil assemblages of major groups show sequential changes near the Oligocene/Miocene (O/M) boundary (23.8 Ma). Many extinction events and some first occurrences of calcareous nannofossils and many occurrences of radiolarians are found from about 24.8 to 23.3 Ma, and first occurrences of planktic foraminifers and diatoms followed from 23.2 through 22 Ma. Hence, the O/M boundary is identified as a significant level for microfossil evolutions.  相似文献   

8.
9.
东北地区保护地土壤真菌多样性研究I   总被引:1,自引:0,他引:1  
20 0 3年4月至2 0 0 4年7月在辽宁、吉林、黑龙江三省的2 0多个市县共采集不同年限的保护地土样15 0多份,采用稀释平板法在孟加拉红培养基上分离近千个真菌菌株,通过纯化培养和形态鉴定,将各菌株鉴定到种。本文报道了部分可培养的子囊菌和有丝分裂孢子真菌的研究结果,其中子囊菌5属6种,包括两个中国新记录种(Lophotrichusbrevirostratus和Microascuscinereus)和一个国内记录但未正式发表的子囊菌(Emericel lopsisterricola) ;有丝分裂孢子真菌7属10种。  相似文献   

10.
In Drosophila, the asymmetric localization of specific mRNAs to discrete regions within the developing oocyte determines the embryonic axes. The microtubule motors dynein and kinesin are required for the proper localization of the determinant ribonucleoprotein (RNP) complexes, but the mechanisms that account for RNP transport to and within the oocyte are not well understood. In this work, we focus on the transport of RNA complexes containing bicoid (bcd), an anterior determinant. We show in live egg chambers that, within the nurse cell compartment, dynein actively transports green fluorescent protein-tagged Exuperantia, a cofactor required for bcd RNP localization. Surprisingly, the loss of kinesin I activity elevates RNP motility in nurse cells, whereas disruption of dynein activity inhibits RNP transport. Once RNPs are transferred through the ring canal to the oocyte, they no longer display rapid, linear movements, but they are distributed by cytoplasmic streaming and gradually disassemble. By contrast, bcd mRNA injected into oocytes assembles de novo into RNP particles that exhibit rapid, dynein-dependent transport. We speculate that after delivery to the oocyte, RNP complexes may disassemble and be remodeled with appropriate accessory factors to ensure proper localization.  相似文献   

11.
12.
The objective of this study was to document the traditional knowledge of plants used for textile dyeing by the Tai-Lao ethnic group in Roi Et province in northeastern Thailand. Traditional knowledge of plants used for textile dyeing is disappearing because of modernization including new lifestyles, urbanization, and the introduction of synthetic colors. Textile dyeing with local plants, however, is experiencing a revival connected to ecotourism and global interest in natural products. To exploit that potential, it is important to preserve the local knowledge related to textile dyeing. We interviewed 60 Tai-Lao informants in 15 villages and 9 districts about their dyeing traditions and the species used through individual semi-structured and focus groups interviews. A total of 56 species in 50 genera and 31 families were used for dyeing cotton and silks; most species belonged to Fabaceae (11 spp., 19%) and Anacardiaceae (5 spp., 9%). Trees (36 spp., 65%) were the best represented life form among the dye plants, followed by shrubs and herbs (8 spp., 16% each), and climbers (4 spp., 7%). Bark was the plant part most commonly used for dyeing (25 spp., 42%) followed by leaves (12 spp., 20%), and fruits (9 spp., 15%). Home gardens were the most common habitat of dye plant (30 spp., 53%) followed by community forests (16 spp., 28%). Indigofera tinctoria L. and Pterocarpus indicus Willd. were the most important dye plant species of the Tai-Lao ethnic group as demonstrated by their high use value index (UV = 0.60). Blue/indigo-blue was the color most informants had common knowledge about with an informant consensus factor (ICF) of 0.92 followed by black with ICF = 0.84. Ten different colors were obtained from the 56 plant species. Brown/pale-brown/golden-brown was the color obtained from most dye plant species (14 spp., 25%) followed by green/pale-green/dark-green (13 spp., 23%). Nine different kinds of mordants were used in the dyeing, including alum, chrome (potassium dichromate; K2Cr2O7), copper sulfate (CuSO4), iron oxide (Fe2O3), tamarind juice (tartaric acid), salt (NaCl), lime (calcium oxide; CaO), ash (potassium hydroxide; KOH), and mud. Among the 56 species used for textile dyeing, three are on the IUCN Red List of Threatened Species, including: Dipterocarpus alatus Roxb. & G.Don, Dipterocarpus obtusifolius Teijsm. ex Miq., and Pterocarpus indicus Willd. Documenting these and other species used for textile dyeing will provide additional arguments for their conservation. It will also help to secure the reappearing tradition of textile dyeing with local plants, and hence support the cultural integrity of the Tai-Lao communities, and serve as an example for other communities in Thailand and elsewhere for preserving their traditional knowledge.  相似文献   

13.
The genetic diversity and distribution of ammonia-oxidizing Archaea (AOA) in nine seasonally frozen soils sampled around the city of Harbin, China, is analyzed based on archaeal amoA gene. Soil samples are divided into four groups by its properties: fertilized/unfertilized mesic (well-balanced supply of moisture) soils and fertilized/unfertilized hydric (abundant of moisture) soils. Clone libraries based on AOA amoA gene polymerase chain reaction products are constructed, and the phylogenetic analysis at 5 % cutoff level shows that AOA members mainly belong to the soil/sediment lineage which includes four clusters, and very few archaeal amoA gene sequences fall into the marine lineage. The four groups of soils have different archaeal amoA gene assemblage, and the available nitrogen and organic carbon are significantly correlated with diversity indexes. The result shows that long-term artificial amendment such as fertilization and agriculture cultivation has an important impact on AOA community shift in terrestrial environment. Moisture may drive the shape of different AOA communities by changing the aerobic environment into anaerobic. Soil composition is another noticeable factor effect AOA community, which can help the shape of a special AOA community with only two species.  相似文献   

14.
The distribution of ammonites across the Jurassic-Cretaceous boundary of the central part of the Russian Platform is discussed. The nomenclature of Craspedites nodiger (Eichwald, 1962) and Hectoroceras tolijense (Nikitin, 1881) is updated. A new species, Craspedites ultimus sp. nov., is described from the basal horizons of the rjasanensis Zone (Ryazanian Stage). The Hectoroceras tolijense and Hectoroceras kochi faunal horizons lying between the nodiger and rjasanensis zones are united in the kochi Zone of the basal Ryazanian. Previous opinions suggesting a hiatus between the Volgian and Ryazanian stages are reviewed and rejected.  相似文献   

15.
Middle to Late Cretaceous permineralized plants hitherto described from Hokkaido, Japan are summarized. The fossil flora comprises fungi, ferns, gymnosperms and angiosperms. Many modern fern families have been recognized including Anemiaceae, Cyatheaceae, Dennstaedtiaceae, Gleicheniaceae Loxsomaceae, Lygodiaceae and Matoniaceae. Gymnosperms are most abundant in the flora. Some recently-found materials are tentatively introduced with brief comments emphasizing their morphological and taxonomical significance. A bisporangiate flower ofCycadeoidella japonica Ogura shows fine internal anatomy and provides evidence that the cycadeoidalean ovule was a cupulate, unitegmic structure. Vascular tracheids in the synangial wall support the evolution of cycadeoidalean synangia from Paleozoic seed-fern synangia. A new gymnosperm female fructification has a thick envelope comparable to an angiosperm carpel around a large seed. The angiosperms contain various morphologies that require further extensive study.  相似文献   

16.
17.
Eggs of the turtle Trionyx spiniferus are rigid, calcareous spheres averaging 2.5 cm in diameter. The eggshell is morphologically very similar to avian eggshells. The outer crystalline layer is composed of roughly columnar aggregates, or shell units, of calcium carbonate in the aragonite form. Each shell unit tapers to a somewhat conical tip at its base. Interior to the crystalline layer are two tertiary egg membranes: the outer shell membrane and the inner shell membrane. The outer shell membrane is firmly attached to the inner surface of the shell, and the two membranes are in contact except at the air cell, where the inner shell membrane separates from the outer shell membrane. Both membranes are multi-layered, with the inner shell membrane exhibiting a more fibrous structure than the outer shell membrane. Numerous pores are found in the eggshell, and these generally occur at the intersection of four or more shell units.  相似文献   

18.
长白山黏菌区系多样性研究   总被引:2,自引:0,他引:2  
对长白山地区黏菌区系进行初步研究,结果如下:含20种以上的大科有5个,分别为绒泡菌科、团毛菌科、钙皮菌科、发网菌科和筛菌科,共含195种,占总种数的92.86%;含10种以上的属有绒泡菌属、团网菌属、筛菌属、双皮菌属、团毛菌属、钙皮菌属和发网菌属,共含144种,占总数的68.57%。从物种的区系成分上看,世界分布和北温带成分占绝对优势,二者占总种数的66.66%。另外,特有成分也较多。说明长白山黏菌区系丰富多彩并具有特色。  相似文献   

19.
半蒴苣苔(Hemiboea subcapitata),为苦苣苔科半蒴苣苔属多年生草本植物。该种形态变异幅度大,曾包括多个变种; 分布范围广,在多种类型的生境基质上皆有分布。该研究的材料包括典型半蒴苣苔和与之近缘且曾被归为其变种的翅茎半蒴苣苔(H. pterocaulis),以及新发现的与两者形态上分别最相近的另两种变异类型,对其关键形态、微形态的多样性进行了描述和比较; 结合查阅标本、文献资料以及长期的野外追踪调查,统计分析了半蒴苣苔不同类型间的地理和生境分布; 通过DNA证据,初步重建各物种及变异类型间的系统发育和单倍型进化关系。结果表明:(1)通过茎、叶、花和开花物候等多性状组合能够区分半蒴苣苔复合群各类型。(2)半蒴苣苔复合群四类型间在叶表皮细胞形状和气孔分布等方面无区别,而在表皮毛的有无、复表皮层数、维管束数量和排布存上存在差别,或有助于分类。(3)典型半蒴苣苔广泛分布于我国中部至南部,向南延伸至越南北部,在石灰岩、丹霞等生境基质上皆有分布; 翅茎半蒴苣苔仅分布于广西桂林市小部分区域的喀斯特山石灰岩基质上; 另两种变异类型分布更为狭域,仅分布于桂林市永福县一个或相邻的数个喀斯特山石灰岩基质上。(4)DNA单倍型网络图分析表明,半蒴苣苔复合群四类型各自独享单倍型; 重建的分子系统发育关系表明,金钟山居群与翅茎半蒴苣苔聚为一支,两者亲缘关系最近但相互之间不成单系,金钟山居群是否为独立物种还需更多证据加以检验; 半蒴苣苔与永福半蒴苣苔两者间互为单系,支持两者为独立物种  相似文献   

20.
The Canning Basin of northwestern Australia is a key area for understanding global changes at the “Kellwasser Events” and the Frasnian‐Famennian boundary. Frasnian stromatoporoid‐coral‐cyanobacterial reef platforms stretched out for enormous distances along the palaeoshelf but in the early Famennian they were completely replaced by cyanobacterial reef platforms. An iridium anomaly in the sequence was formerly believed to be at or close to the boundary and was interpreted as possible evidence for an asteroid impact. Recent field work and detailed biostratigraphy in the area east and southeast of Fitzroy Crossing has given dating relevant to the timing and extent of sea level changes, hypoxic incursions and reef backstepping. Goniatites and conodonts provide correlations with the international biostratigraphy.

In the Horse Spring area the stage boundary falls within the Virgin Hills Formation which normally has a rich pelagic goniatite, nautiloid and conodont fauna. In the latest Frasnian (Zone 13 of Klapper 1989; regional Sphaeromanticoceras lindneri Zone) large allochthonous reef blocks moved downslope into the open marine basin. A diverse gastropod fauna is associated with the last atrypid brachiopods. The faunal record at the immediate boundary is obscured by dolomitisation but manticoceratid goniatites range into this level. There is no evidence for the organic‐rich dark Kellwasser limestone facies.

In the McWhae Ridge area two Frasnian goniatite horizons with Beloceras trilobites and the giant Mamicoceras guppyi and Sphaeromanticoceras lindneri transgress over the reef slope. Stromatolitic cyanobacterial beds mark condensations. Again there is no trace of the oxygen‐depleted Kellwasser facies. However, as at Horse Spring, manticoceratids persisted into dolomitic marker beds that have no other preserved macrofauna. The iridium anomaly associated with Frutexites postdates the Frasnian‐Famennian boundary and was formed by cyanobacterial concentration.  相似文献   

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