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1.
描述了发现于广西靖西果乐寒武系芙蓉统果乐组的始海百合化石,确定其为始海百合纲Ridersiidae科一新属:Jingxieocrinus gen.nov.。新属特征如下:个体较小,锥形萼。萼板15块,排列规则,其中五边形底板5块,六边形侧板5块,五边形辐板5块,无萼孔及缝孔。茎长,始端粗,向末端迅速变尖。始端茎板矮,大小茎板交互重叠,向末端茎板变高,大小茎板趋于一致。腕羽5枝,细长不分叉,双列小板,生于口缘辐板相间处。偶见盖板,横椭圆形,上覆放射状纹饰。模式种Jingxieocrinus guoleensis gen.et.sp.nov.的茎细且长,末端变尖,没有固着器,可能以茎末端附着于其它物体上营假浮游或寄生漂游生活。  相似文献   

2.
1961年,本所赵金科教授与陈旭同志在测制川北广元中子铺志留纪地层剖面时,于中子铺附近的中志留统罗惹坪群中获得一个保存良好的海百合蕚部化石。这个蕚部标本经详细研究,为属于古海百合科(Palaeocrinidae)的一个新属。兹取名为雕刻海百合属(Caelocrinus),因为这个蕚部标本表面的横棱脊(TR)特别发育,如同雕刻,故名。新属雕刻海百合的外形具有雕塑海百合科(Dolatocriaidae)的形态特征;但根据其骨板组织的构造,新属与雕塑海百合科差别极大,而应属于古海百合科。古海百合科的特征是:双环海百合,棱部呈截锥至球状:辐肛板(RA)直接或偏斜于右后辐板(RPR)之下,不和内底板(IBB)接触;肛板(XX)1—3,主要的肛板和辐板(RR)平列;不见肛管;蕚盖坚固;腕(BrBr)短,简单或一次分叉;柄圆(图1)。根据吴巴士(Obaghs,G.1953)的分类,这个科过去共有六个属,如下:  相似文献   

3.
本文对烟台海域海月水母水母体阶段伞径、腕长及体重的生长规律进行了研究,并首次对其生长过程中水管系统的发育进行了观察。结果表明,在人工培养条件下,海月水母体重(W)与伞径(D:15~150㎜)呈幂函数增长;腕长(L)与伞径(D)呈线性关系;伞径生长曲线方程为:Dt = 4×10-6t4-0.0014t3 0.1087t2 0.5079t 9.428 (R2=0.9993)。。海月水母初生碟状体出现主辐管与间辐管,3日龄时碟状体出现从辐管,11日龄时出现环管、分离点。随着水母的生长,伞径增大,水管系统的分离点数与聚合点数逐渐增多,成熟时1/4伞部分离点数最多为66个,聚合点数最多为32个。  相似文献   

4.
1959年夏,笔者在南京北郊迈皋桥西北石炭山,采到一种形态罕见的化石。它产于上二迭统龙潭组炭质泥岩中,共生的化石有腕足类、头足类、瓣鳃类和少量植物碎片。标本以黄铁矿浸染方式保存,与空气接触即氧化成为暗黑色。当时,笔者误认为是植物化石,后经显微镜下观察,确定为动物化石,但由于形态特别,长期无法确定其分类位置。经过长期反复详细观察,最后认为它属于棘皮动物门中的海羊齿科。海羊齿科Antedoniidae海羊齿属Antedon Freminville,1811Antedon sp.(图版Ⅰ,图1—4)描述:标本仅保存数个羽腕,一个正型(外模),二个副型(内模),前者中部略遭破损,但仍可清晰地看出其整个外貌。乳白色,羽状:腕一次分歧,羽肢呈管状,对生或近于对生,基部略收缩;腕的表面呈不明显凸起,有与羽肢相通的  相似文献   

5.
Neoarchaeocrinus在我国的发现   总被引:1,自引:0,他引:1  
王耀 《古生物学报》1995,34(3):343-349
根据贵州石阡雷家屯志留系剖面的1块海百合化石标本建立了一新种:Neoarchaeocrinusshiqianensissp.nov。该种以较长大的初级间腕板及辐板脊与腕板脊围成菱形等特征区别于属内其他种。  相似文献   

6.
端足类(Amphipoda〕是海洋中常见的浮游动物,属于甲壳动物软甲亚纲,由于生活习性不同,分为三个亚目:(虫戎)亚目(Hyperidea)、钩虾亚目(Gammaridea)和麦杆虫亚目(Caprellidea)。只有(虫戎)亚目是完全在海洋营浮游生活的,其它大多数种类营底栖生活。其种属相当复杂,个体大小差异显著,形态多样。头部形态是分类的主要特征,其形态变化与环境有关,有些种类能巧妙的栖息在其他动物体上,如胖短脚(虫戎)  相似文献   

7.
辐鳍鱼亚纲是现存脊椎动物中最大的类群,包括腕鳍鱼次亚纲、辐鳍鱼次亚纲(包括软骨硬鳞类和新鳍鱼类)和亲缘关系密切的化石类群。已灭绝的翼鳕属(Pteronisculus)是隶属于辐鳍鱼亚纲的一个干群,包括产于马达加斯加、欧洲和北美下三叠统的11个种和中国中三叠统的一个种。根据滇东罗平中三叠世(安尼期)海相地层中发现的5块保存完好的化石,命名翼鳕属一新种,张氏翼鳕(Pteronisculus changae sp. nov.)。这是翼鳕属在中三叠世的第二个确切种,最大体长达295 mm,代表了罗平生物群中已知体型最大的辐鳍鱼亚纲干群物种。新种具有翼鳕属的独特衍征,泪骨具有牙齿,但它又有明显区别于本属其他种的自近裔特征,如间颞骨中部有一个内突起,21根上神经骨,83列侧线鳞。分支分析结果为早期辐鳍鱼类系统发育关系提供了新的见解,认为翼鳕属是Cyranorhis的姐妹群。根据体型和口缘牙齿等特征推测张氏翼鳕是一个快速游动的捕食者,以浮游无脊椎动物和体型较小的鱼类或鱼类幼体为食。作为翼鳕属最年轻的成员之一,张氏翼鳕的发现进一步表明翼鳕的多样性比我们过去认识的要高,古特提斯洋东缘可能是该属在中三叠世早期的避难所。  相似文献   

8.
武汉东湖浮游病毒的丰度及多样性   总被引:5,自引:0,他引:5  
运用透射电镜及荧光显微技术 ,对富营养化的武汉东湖中浮游病毒丰度及多样性进行了研究。电镜观察和计数结果显示 ,东湖中浮游病毒的丰度达到 10 8个 /mL。荧光显微镜计数结果约是电镜计数结果的 2 72倍 ,差异极显著 (P <0 0 1)。在东湖超富营养区的水样中观察到了多种与各种病毒形态类似的颗粒 ,其中大部分与噬菌体和噬藻体类似 ,具多种形态的尾部和六边形头部。还有一些线状、杆状、子弹形等形态的病毒粒子。研究结果显示东湖水环境中的浮游病毒不仅丰度极高 ,而且种类丰富。提示浮游病毒在东湖水环境和水生态系统中可能扮演重要角色。  相似文献   

9.
李俊  任毅 《西北植物学报》2008,28(2):267-271
对马兜铃属植物北马兜铃(Aristolochia contorta Bge.)花形态发生的扫描电镜观察表明:其花萼在发生时与苞片相似,6枚雄蕊呈4枚先发生、2枚后发生的方式,心皮的发生以6个胎座突出到子房室中为特征,由侵入的侧膜胎座合生为中轴胎座。在胎座发生发育过程中,在花药的腹面各产生一个突起,此突起后来与胎座上端相连,最终发育为合蕊柱裂片。结合文献资料,我们认为北马兜铃的花被与苞片是同源的,其合蕊柱裂片来自于雄蕊,中轴胎座是次生的。  相似文献   

10.
关岭新铺晚三叠世早期卡尼期(Carnian)龙层及其下伏竹杆坡组上、中部的腕足类从上到下可划分为Linguloid,Laballa,Pseudokoninckina等3个化石群落。根据各群落特征分子的固着方式、生活习性、贝体形态和大小,以及与其他生物共同埋藏情况,并考虑围岩性质等方面的综合因素,得出Pseudokoninckina群落的古生态底域位于BA4内侧至BA3外侧,Laballa群落的古生态位置相当于BA2,而Linguloid群落则为BA1。在此基础上进一步阐明关岭新铺从竹杆坡组中部至龙层呈现明显海退过程,其古生态底域位置从BA4内侧至BA3外侧一直退到BA1。依据此变化绘出新铺卡尼期海平面下降示意图。对创孔海百合被一些学者推断为假浮游的生活方式提出质疑和讨论,得出当时创孔海百合不可能为假浮游的生活方式,它们应是营底栖的。  相似文献   

11.
The following paper describes the foraminiferal fauna and associated faunal assemblages of the bedded and reef carbonates of the Upper Triassic (most probably Rhaetian) Nayband Formation, which are exposed in a section south of the small town of Bagher-Abad, northeast of Esfahan. Foraminifers are extremely rare in sponge- or coral-dominated bioconstructions and in the bedded carbonates of the Nayband Formation in central Iran. Some carbonate beds are composed of bioclastic wackstone/packstone. These are exposed in the solenoporacean horizon at the uppermost part of the section. Here, the aulotortid- and trocholinid-type foraminifers are relatively abundant. The following foraminiferal taxa with different abundances were found within the carbonates of the investigated section: Trocholina umbo Frentzen, T. turris Frentzen, T. gracilis Blau, Aulotortus tumidus (Kristan-Tollmann), Aulotortus tenuis (Kristan), Aulotortus friedli (Kristan-Tollmann), Coronipora etrusca (Pirini), Semiinvoluta clari Kristan, Turrispirillina? licia variabilis Blau, Galeanella? laticarinata Al-Shaibani, Carter and Zaninetti, Ophthalmidium sp., Agathammina sp., “Sigmoilinaschaeferae Zaninetti, Planiinvoluta carinata Leischner, Planiinvoluta sp., Nubecularia sp., Endothyra sp., Paeolituonella sp. and some sessile agglutinated and nodosariid types. All mentioned taxa are very rare, except the involutinid and trocholinid types. The following species are described as new: Trocholina blaui nov. sp., Spirilina? iranica nov. sp., and Coronipora serraforma nov. sp. Trocholina blaui is usually attached to solenoporacean thalli. Four foraminiferal associations, which are named after the occurrence of the abundant species, were distinguished as Aulotortus tumidus association, Aulotortus friedli association, Trocholina umbo association, and Trocholina blaui association. Aulotortid types and Trocholina umbo were found within the bioclastic wackstone/packstone carbonates. Trocholina blaui is abundant in solenoporacean framestones. The foraminiferal association of investigated carbonates contains a mixed fauna, known from Upper Triassic–Liassic in the Tethyan realm. Carbonates of the whole investigated section are dated—due to occurrence of the genus Aulotortus, with species A. tumidus (Kristan-Tollmann), A. tenuis (Kristan), and A. friedli (Kristan-Tollmann)—as Upper Triassic (most probably Rhaetian). The “typical” foraminifers occurring in the reef biotopes in the northwestern Tethys are either missing or extremely rare in the Iranian bioconstructions.  相似文献   

12.
The secular trend of pubertal development in Chile is analysed on the basis of three cross-sectional studies performed in 1887, 1940 and 1970.A tendency for menarche to occur at earlier ages is observed. There is a rate of decrease of 0·066 years per decade in the period between 1887 and 1940 and of 0·29 years per decade in the last 30 years.In 1970 girls aged 10 to 17 years were taller than those in 1940 at similar socioeconomic levels. In weight, the effect of socioeconomic level seems important, thus in the sample of 1940 girls in the higher socioeconomic level were the heaviest and in the sample of 1970 both socioeconomic levels presented similar weight although the well-off sample was taller.The weight/height3 index clearly shows two effects: first, that girls in 1970 had a lower index than those in 1940. Second, the effect of socioeconomic level was not the same in 1940 and 1970; in the former year the low socioeconomic groups had a lower index than that of high socioeconomic groups, whereas the reverse was found in 1970.  相似文献   

13.
Plasma-membrane fragments recovered in the microsomal fraction of rat liver homogenates were shown to be heterogeneous in density. It was demonstrated that 5'-nucleotidase, the most commonly used plasma-membrane marker, is concentrated in the lightest subfraction. Two of the published procedures for the isolation of plasma-membrane fragments from the microsomal fraction (Touster et al., 1970; Hinton et al., 1971) are shown to give products which are not representative of all the plasma-membrane fragments of microsomal size, and it is argued that a third procedure (House & Weidemann, 1970) is likely to give a similar product.  相似文献   

14.
1970-79 US fertility trends among differnet racial, regional, age, educational, parity, and socioeconomic subgroups in the population were examined, using own children data from the 1976 Survey of Income and Education (SIE) and the March Current Population Surveys (CPS) from 1968-80. In addition, cross-sectional differences in fertility for the subgroups were compared for 1970 and 1976, using multiple regression analysis. 1st, the appropriateness of using fertility rates obtained from own children data was assessed by comparing fertility rates obtained from the SIE data with those derived from vital statistic and census data. The comparative analysis confirmed that the SIE data yielded an accurate estimate of period fertility rates for currently married women, provided the subgroup samples were sufficiently large. CPS fertility estimates were also judged to be accurate if data from 3 adjacent survey years was pooled to increase sample size. Fertility trends for 5 educational groups were assessed separately for 1967-73. During this periold, there was a marked decline in fertility for all 5 groups; for the group with 5-8 years of education the decline was only 14%, but for the other 4 groups, which included women with 9-16 or more years of education, the decline in fertility ranged from 26-29%. In assessing the 1970-76 trends, the sample was restricted to own children, aged 3 years or less, of currently married women, under 40 years of age. Among whites, there was an overall 20% decline in fertility between 1970-76 and an overall fertility increase of about 2% between 1976-79. These trends were observed in all 28 white subgroups. A similar pattern was observed for blacks. There was an overall fertility decline of 24% between 1970-76, and this decline was apparent for all subgroups except women with college degrees. Betwen 1976-79, black fertility rates, unlike white rates, continued to decline, but the rate of decline was only 3%. Furthermore, the decline in almost all the black subgroups was markedly less than in the 1970-76 periold, and for many of the subgroups the trend was reversed and fertility increased. In summary, the fertility trends noted for 1970-79 were pervasive for almost all the subgroups for both blacks and whites; i.e., there was a marked decline in fertility between 1970-76 and than a reversal or slowing down of the decline during the 1976-79 for all black and white subgroups. Cross-sectional fertility differences in the subgroups in 1970 and in 1979 were quite similar, and fertility rates differed markedly for the separate subgroups. These differences do not, of course, explain the pervasive trends observed in the analysis of the fertility rates over time. A similar study assessing fertility trends among subgroups for the early 1940's through the late 1960s also revealed the pervasive nature of period fertility trends. Demographers have not as yet been able to explain these shifts in fertility that cut across all subgroups in the US and which also characterize the period fertility rates in other developed countries. Tables provided information on 1) total fertility rates by educational level and by geographical region for 1945-1975; 2) % change in number of own children less than 3 years of age among women under age 40 by maternal age, maternal education, initial parity, geographical region, and husband's income; and 3) mean number of own children less than 3 years of age among women under age 40 by maternal age, education, parity, region, and husband's income.  相似文献   

15.
Data from quantitative samples of the benthos at a 200-m site in central Puget Sound, collected twice yearly in most years between 1963 and 1992, were evaluated to determine the extent to which species composition in a continental-shelf depth community exhibits long-term persistence. Study results showed that the most abundant species were consistently present over the 30-year period. However, measures of species composition (e.g., similarity, diversity) reveal a subtle, gradual change in the community over time. Among the changes are (1) multi-year periods of greatly increased abundance of the common species; (2) an overall increase in the total abundance of the benthic community beginning in the mid-1970s; (3) periods of increased abundance, during the late 1970s and early 1980s, of two species that are tolerant of organic enrichment; and (4) the steady decline in abundance of the large burrowing echinoderm, Brisaster latifrons as a consequence of the lack of recruitment to the site since 1970. Despite the conspicuousness of these changes, there are no observed environmental factors that readily explain them. Circumstantial evidence suggests that climate-related change in Puget Sound circulation beginning in the mid-1970s, organic enrichment associated with a nearby large source of primary-treated sewage, and the influence of changes in the abundance of the large echinoderms on the smaller species are potential agents of change. The principle reasons for our inability to identify causes of long-term change in the Puget Sound benthos are (a) inconsistent long-term monitoring of environmental variables, (b) the lack of quantitative information about long-term changes in plankton and fish populations, (c) lack of knowledge of specific predator/prey and competitive interactions in soft bottom benthos, (d) unknown influence of moderate levels of contamination on biota; and (e) lack of understanding of possible linkages between climate regime shifts and fluctuations in local biological populations.  相似文献   

16.
Clinical reflux was first visualized over 100 years ago. In the 1950s and early 1960s, the assumption was that surgery to relieve bladder neck obstruction would have a positive effect on bladder function and reflux. By the early 1970s it was understood that the underlying structural problems leading to primary reflux were congenitally abnormal distal ureters and orifices. Researchers in the 1960s and 1970s demonstrated the connection between reflux and renal scarring. More recently, reflux nephropathy in the absence of urinary tract infections has been observed, leading researchers to investigate an association between bladder dysfunction and reflux with resulting nephropathy. The cornerstone of management of the child with vesicoureteral reflux is antibiotic prophylaxis; treatment regimens for various grades of reflux are reviewed. Indications for surgical treatment of reflux are also discussed. Controversies regarding vesicoureteral reflux, including duration of prophylactic treatment, remain to be resolved.  相似文献   

17.
Using historical (1970) and more recent (1996) Lake Erie plankton and trophic status data, we developed a Planktonic Index of Biotic Integrity (P-IBI) to measure changes in lake ecosystem health. We used discriminant analysis to determine phytoplankton and zooplankton community characteristics (metrics) that distinguished among levels of impairment. Traditional measures of lake trophic status classes (i.e., oligotrophic, mesotrophic, eutrophic), such as chlorophyll a and total phosphorus concentrations, were used to classify sites on a gradient of impairment. We then judged the ability of plankton metrics to distinguish among trophic status classes. Because of the temporal variability found in plankton communities, we conducted analyses on a monthly basis (May–September). For June, July and August we found five unique metrics that could distinguish among trophic status classes. The P-IBI showed an increase in water quality in Lake Erie between 1970 (<3 = eutrophic) and the mid-1990s (1996 and 1997) (3–4 = mesotrophic) (which reflected mean (±standard error) total phosphorus concentrations (μg/L) 1970 > 1996; western basin (41.53 ± 2.68 > 29.75 ± 1.39), eastern basin (14.84 ± 0.82 > 7.74 ± 0.28) and mean (±standard error) chlorophyll a concentrations (μg/L) uncorrected for pheophytin 1970 > 1996; western basin (12.58 ± 1.82 > 5.40 ± 0.22), central basin (5.90 ± 0.36 > 3.17 ± 0.54), and eastern basin (5.17 ± 0.38 > 1.67 ± 0.18)), with declining water quality in the late 1990s (1998 and 1999) (3) and 2002 (<3). We recommend that the techniques used in creating the P-IBI be investigated for determining ecosystem health of other lakes.  相似文献   

18.
Continuing investigations on the South Amherst Drosophila melanogaster natural population following the significant decline and recovery of lethal (le) and semilethal (sle) frequencies in the late 1960's (Ives, 1970) show that the population has been remarkably stable although it contains MR (male recombination) and/or P DNA elements (Kidwell et al., 1977a; Green, 1980). A 13-year study affirms that the lethals present are nonrandomly distributed along the second chromosome and deficient on the right; they differ significantly in distribution from spontaneous (Ives, 1973) and δ-induced lethals (Minamori and Ito, 1971). Between 1970 and 1977, a total of 4,083 second chromosomes from the Markert subpopulation were analyzed; 28.9% of the chromosomes were lethal and 7.25% were semilethal in homozygous condition. Frequencies are similar for early summer and late fall collections although the rate of allelism among lethals is significantly higher in early summer than in late fall. For the large fall (1970–1979) Porch site population, 2,519 second chromosomes were analyzed; 29.5% were lethal and 8.0% were sublethal as homozygotes; the rate of allelism among lethals was 1.50%. At Hockanum, 1977–1983, lethal and semilethal frequencies were lower; the rate of allelism among lethals was 1.43%. The chromosome map distribution of lethals does not change between summer and late fall at Markert. The overall distributions of lethals at the Markert and Hockanum sites are similar. In tests for male recombination (MR) activity in the population over a 6-year period, a total of 0.47% recombinants were observed; these were uniformly distributed along the second chromosome. Comparisons are made with other long studied D. melanogaster populations.  相似文献   

19.
1.  The populations of many UK farmland birds declined between 1970 and 1990, frequently accompanied by contractions in breeding ranges. Ornithological atlas data, land use data and environmental data at the scale of 10-km squares were used to investigate the relationship between local extinctions and habitat suitability for six species, and to predict where future losses are most likely.
2.  For each species we tested the hypothesis that local extinctions were concentrated in environments that were inherently less suitable. We also tested the hypothesis that spatial patterns of loss were not independent between species due to their concurrence in the same habitats.
3.  Multivariate analyses (PCA) showed that areas where each species became extinct between 1970 and 1990 were more similar in land use type, climate and topography to areas where a species was never present than those where it was retained; local extinction was more likely in less suitable environments. Multiple logistic regression showed that for five of the six species the environmental gradient best predicting presence or absence in 1970 was also that best predicting loss between 1970 and 1990. For the six species studied, local extinctions were least likely in lowland arable areas.
4.  For any pair of species, local extinctions were more frequent outside the area of overlap of the two species' ranges than inside. Within the area of overlap, species tended to be lost from the same squares. For each species, likelihood of local extinction declined with increasing number of the other five species present.
5.  We used model parameters to map the probability of future local extinctions of the six species considered, allowing the identification of key areas for conservation management at a spatial scale appropriate to agri-economic incentives.  相似文献   

20.
A pair of chimeric twins, T.S. (male) and M.R. (female), were examined. The amounts of 'foreign' blood cells in each twin found on three occasions were compared. The percentages of M.R. cells found in the blood of T.S. in 1977 and in 1982 were similar and about 1/5 of that found in 1970. The amount of T.S.-blood cells found in M.R. was declining slowly from about 31% in 1970 to about 25% in 1982.  相似文献   

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