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1.
Birds known from more than isolated skeletal elements are rare in the fossil record, especially from the European Mesozoic. This paucity has hindered interpretations of avian evolution immediately prior to, and in the aftermath of, the Cretaceous-Tertiary (K-T) extinction event. We report on a specimen of a large ornithurine bird (closely related to Ichthyornis) from the uppermost Cretaceous (Maastricht Formation) of Belgium. This is the first record of a bird from these historic strata and the only phylogenetically informative ornithurine to be recovered from the Mesozoic of Europe. Because this new specimen was collected from 40 m below the K-T boundary (approximate age of 65.8 Ma), it is also the youngest non-neornithine (=non-modern) bird known from anywhere in the world.  相似文献   

2.
The Crotophaginae is a subfamily of New World cuckoos comprising the monotypic genus Guira and three ani species (Crotophaga). All exhibit a rare form of cooperative breeding known as plural female joint-nesting, whereby two or more females lay eggs in a single nest. I reconstructed the phylogeny of Crotophaginae using the mitochondrial genes cytochrome oxidase I, II, and III, ATPase 6 and 8, and cytochrome b. The subfamily was monophyletic, implying a single origin of cooperative breeding in New World cuckoos. Crotophaga was also monophyletic with Guira as its sister taxon. Within Crotophaga, the smooth-billed (C. ani) and groove-billed (C. sulcirostris) anis formed the internal clade with the greater ani (C. major) basal to this pair. This phylogeny is consistent with differences in reproductive patterns and social organization exhibited by crotophagine cuckoos, and will serve as a framework for future study of the evolution of cooperative breeding in this subfamily.  相似文献   

3.
A new maniraptoran dinosaur from China with long feathers on the metatarsus   总被引:2,自引:0,他引:2  
The unusual presence of long pennaceous feathers on the feet of basal dromaeosaurid dinosaurs has recently been presented as strong evidence in support of the arboreal–gliding hypothesis for the origin of bird flight, but it could be a unique feature of dromaeosaurids and thus irrelevant to the theropod–bird transition. Here, we report a new eumaniraptoran theropod from China, with avian affinities, which also has long pennaceous feathers on its feet. This suggests that such morphology might represent a primitive adaptation close to the theropod–bird transition. The long metatarsus feathers are likely primitive for Eumaniraptora and might have played an important role in the origin of avian flight.Electronic Supplementary Material  Supplementary material is available for this article at  相似文献   

4.
In 1993, several unusual horn sheaths, collected in the South of Vietnam, were regarded as evidence for a new mammal species, Pseudonovibos spiralis. However, the taxonomic status of P. spiralis remains a highly controversial subject: firstly, it has been related to three different groups of the family Bovidae: Antilopini (gazelles), Bovini (oxen, bisons, and buffaloes), and Caprini sensu lato (goats, sheep and allies). Secondly, certain horns have been shown to be faked. Most recently, it has been suggested, on the basis of 12S rRNA gene sequences, that P. spiralis was a new species of buffalo. I demonstrate here that this conclusion was inaccurate, and base this on the grounds that: (1) the putative sequence of P. spiralis is shown to be a chimera obtained from three different species: Bos taurus, Bubalus bubalis and Saiga tatarica, and (2) several factors indicate that the specimen used was not authentic. This new study confirms earlier suggestions that the horns used to formally describe P. spiralis were bogus and were in fact derived from the horns of domesticated cattle (Bos taurus). The data suggest that P. spiralis never existed.  相似文献   

5.
目的为提升战场电磁环境环境复杂度评估的客观性,基于电磁环境与通信性能的相关性提出一种电磁环境复杂度评估方法。方法该方法以层次分析法和混合加权理论为基础,以典型通信系统为例,建立语音通信和数据通信设备性能和电磁环境复杂度等级的映射,并据此建立通信网系性能和电磁环境复杂度的等级映射,从目标层、准则层、指标层给出五级量化指标体系。结果在50 km×50 km典型地域中,上述评估方法给出了10部高频和10部超高频通信设备组成的通信网络各单链路通信质量,分别为Ⅳ、Ⅳ、Ⅰ、Ⅳ、Ⅲ、Ⅱ、Ⅳ、Ⅴ、Ⅳ、Ⅲ、Ⅱ、Ⅱ、Ⅲ、Ⅴ、Ⅱ、Ⅰ、Ⅴ、Ⅳ、Ⅴ、Ⅴ,并在此基础上评估了整个网系的通信质量等级和整个通信网系面临的电磁环境复杂度(Ⅳ)。结论上述研究验证了方法的可行性,同时证实了同一环境下不同设备所受的电磁环境影响具有个体差异性,整体通信网系的受影响程度有别于单一设备。研究结果可为通信网系的电磁环境适应性试验、电磁干扰效应评估等研究提供基础和有益的参考。  相似文献   

6.
7.
TheeffectoflightontheMn(II)orFetlll)xatalyzedoxidationofaqueousS(IV)XuYongfu(InstituteofAtmosphericPhysics,ChineseAcademyofSc...  相似文献   

8.
With only one known exception, early Cretaceous birds were smaller than their closest theropod dinosaur relatives. Here we report on a new bird from the Early Cretaceous feathered-dinosaur-bearing continental deposits of Liaoning, northeast China, which is not only larger than Archaeopteryx but is nearly twice as large as the basal dromaeosaur Microraptor. The new taxon, Sapeornis chaoyangensis gen. et sp. nov., has a more basal phylogenetic position than all other birds except for Archaeopteryx. Its exceptionally long forelimbs, well-developed deltoid crest of the humerus, proximally fused metacarpals, relatively short hindlimbs and short pygostyle indicate powerful soaring capability and further suggest that by the Early Cretaceous ecological diversification of early birds was greater than previously assumed. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-001-0276-9.  相似文献   

9.
Ecological interactions of conifers and coniferophagous bark beetles are determined in part by terpenoids (isoprenoids), which are major defense metabolites of conifer oleoresin. Curiously, similar compounds are important aggregation pheromones of conifer-attacking bark beetles. Terpene synthases are responsible for generating the enormous variety of terpenoid carbon skeletons found in nature. These catalysts convert short-chain prenyl diphosphates to a diverse assortment of hemiterpene, monoterpene, sesquiterpene, and diterpene natural products. While terpene synthases have frequently been characterized from plant and microbial sources, they have not yet been described in animals. Here we report the discovery of a monoterpene synthase activity in an insect, the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae). Cell-free assays of I. pini revealed that geranyl diphosphate (GDP) is converted to the acyclic monoterpene myrcene in whole-body extracts from males, but not females. Furthermore, the monoterpene synthase activity in males can be induced by prior treatment with juvenile hormone III (JH III) or by feeding on phloem from the host trees, Jeffrey pine (Pinus jeffreyi Grev. &; Balf.) or red pine (Pinus resinosa Ait.). The sex-specificity and endocrine induction of this activity argue for its involvement in the biosynthesis of monoterpenoid pheromones mediated by enzymes from insect tissue. This discovery is the first example of a monoterpene synthase in the Metazoa and evokes exciting new questions about the origin, evolution, and occurrence of terpene synthases.  相似文献   

10.
Antimony (Sb) is a recognized priority pollutant with toxicity that is influenced by its migration and transformation processes. Oxidation of Fe(II) to Fe(III) oxides, which is a common phenomenon in the environment, is often accompanied by the formation of Mn(III/IV) and might affect the fate of Sb. In this study, incorporated Mn(III) and sorbed/precipitated Mn(III/IV) associated with lepidocrocite were prepared by adding Mn(II) during and after Fe(II) oxidation, respectively, and the effects of these Mn species on Sb fate were investigated. Our results indicated that the association of these Mn species with lepidocrocite obviously enhanced Sb(III) oxidation to Sb(V), while concomitantly inhibiting Sb sorption due to the lower sorption capacity of lepidocrocite for Sb(V) than Sb(III). Additionally, Mn oxide equivalents increased in the presence of Sb, indicating that Sb oxidation by Mn(III/IV) associated with lepidocrocite was a continuous recycling process in which Mn(II) released from Mn(III/IV) reduction by Sb(III) could be oxidized to Mn(III/IV) again. This recycling process was favorable for effective Sb(III) oxidation. Moreover, Sb(V) generated from Sb(III) oxidation by Mn(III/IV) enhanced Mn(II) sorption at the beginning of the process, and thus favored Mn(III/IV) formation, which could further promote Sb(III) oxidation to Sb(V). Overall, this study elucidated the effects of Mn(III/IV) associated with lepidocrocite arisen from Fe(II) oxidation on Sb migration and transformation and revealed the underlying reaction mechanisms, contributing to a better understanding of the geochemical dynamics of Sb.  相似文献   

11.
King brown snakes or mulga snakes (Pseudechis australis) are the largest and among the most dangerous and wide-ranging venomous snakes in Australia and New Guinea. They occur in diverse habitats, are important predators, and exhibit considerable morphological variation. We infer the relationships and historical biogeography of P. australis based on phylogenetic analysis of 1,249 base pairs from the mitochondrial cytochrome b, NADH dehydrogenase subunit 4 and three adjacent tRNA genes using Bayesian, maximum-likelihood, and maximum-parsimony methods. All methods reveal deep phylogenetic structure with four strongly supported clades comprising snakes from New Guinea (I), localities all over Australia (II), the Kimberleys of Western Australia (III), and north-central Australia (IV), suggesting a much more ancient radiation than previously believed. This conclusion is robust to different molecular clock estimations indicating divergence in Pliocene or Late Miocene, after landbridge dispersal to New Guinea had occurred. While members of clades I, III and IV are medium-sized, slender snakes, those of clade II attain large sizes and a robust build, rendering them top predators in their ecosystems. Genetic differentiation within clade II is low and haplotype distribution largely incongruent with geography or colour morphs, suggesting Pleistocene dispersal and recent ecomorph evolution. Significant haplotype diversity exists in clades III and IV, implying that clade IV comprises two species. Members of clade II are broadly sympatric with members of both northern Australian clades. Thus, our data support the recognition of at least five species from within P. australis (auct.) under various criteria. We discuss biogeographical, ecological and medical implications of our findings.Electronic Supplementary Material  Supplementary material is available in the online version of this article at  相似文献   

12.
We report the prenatal diagnosis at 16 weeks' gestation of bilateral split-hand/split-foot malformation (SHSFM) with severe lobster claw deformity of hands and feet in a male fetus without associated malformations. A minor manifestation of SHSFM was present in the father with only mild bilateral foot involvement (syndactyly I–II; cleft II–III; left cutaneous syndactyly III–IV). Mutation analysis of the p63 gene on chromosome 3q27 showed a missense mutation 577A→G (predicting amino acid substitution K193E) in the father. This mutation has not been reported so far in SHSFM but resembles the previously reported 580A→G (predicting amino acid substitution K194E) in a family with SHSFM. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

13.
The length ratio between individual digits differs between males and females in humans, other mammals, lizards, and one bird species. Sexual dimorphism in digit ratios and variation among individuals of the same sex may depend on differential exposure to androgens and estrogens during embryonic life. Organizational effects of sex hormones could cause the observed correlations between digit ratios and diverse phenotypic traits in humans. However, no study has investigated experimentally the effect of prenatal estrogens on digit ratios. We analyzed the effect of estradiol injection in ring-necked pheasant (Phasianus colchicus) eggs on digit ratios. Males from control eggs had higher ratios between the second or third and the fourth digit of the right foot compared to females. Estradiol-treated eggs produced males with lower (feminized) right foot second to fourth digit ratio. Thus, we provided the first experimental evidence that prenatal exposure to physiologically high estrogen levels affects bird digit ratios.  相似文献   

14.
经1984—1986年的研究,在掌握三峡库区鸟类资源现状及特点的基础上对国内已建水库鸟类的变动情况进行考察,了解影响鸟类的各种因素,研究这些生态因子对鸟类群落的影响,采用统计学方法量化三峡工程对鸟类资源的影响程度,作出定性、定量的预断评价。 研究结果表明,兴建三峡水库必将引起适应原有生态环境的鸟类群落在组成、生态分布等方面的变化,一方面使珍稀鸟类、经济鸟类受到破坏,使已趋贫乏的森林鸟类更加贫乏;另一方面水禽资源将会增长。但总的影响是弊大于利。建坝150m和180m对不同群落的影响各异。高坝对森林和农田鸟类不利影响值均大于低坝30%;对水域鸟类的有利影响值,高坝为低坝的两倍。  相似文献   

15.
Evaluation and analysis of water quality variations were performed with integrated consideration of water quality parameters, hydrological-meteorologic and anthropogenic factors in Cao-E River, Zhejiang Province of China. Cao-E River system has been polluted and the water quality of some reaches are inferior to Grade V according to National Surface Water Quality Standard of China (GB2002). However, mainly polluted indices of each tributary and mainstream are different. Total nitrogen (TN) and total phosphorus (TP) in the water are the main polluted indices for mainstream that varies from 1.52 to 45.85 mg/L and 0.02 to 4.02 mg/L, respectively. TN is the main polluted indices for Sub-watershed Ⅰ, Ⅱ, Ⅳ and Ⅴ(0.76 to 18.27 mg/L). BOD5 (0.36 to 289.5 mg/L), CODMn (0.47 to 78.86 mg/L), TN (0.74 to 31.09 mg/L) and TP (0 to 3.75 mg/L) are the main polluted indices for Sub-watershed Ⅲ. There are tow pollution types along the river including nonpoint source pollution and point source pollution types. Remarkably temporal variations with a few spatial variations occur in nonpoint pollution type reaches (including mainstream, Sub-watershed Ⅰ and Ⅱ) that mainly drained by arable field and/or dispersive rural dwelling district, and the maximum pollutant concentration appears in flooding seasons. It implied that the runoff increases the pollutant concentration of the water in the nonpoint pollution type reaches. On the other hand, remarkably spatial variations occur in the point pollution type reaches (include Sub-watershed Ⅲ, Ⅳ and Ⅴ) and the maximum pollutant concentration appears in urban reaches. The runoff always decreases the pollutant concentration of the river water in the seriously polluted reaches that drained by industrial point sewage. But for the point pollution reaches resulted from centralized town domestic sewage pipeline and from frequent shipping and digging sands, rainfall always increased the concentration of pollutant (TN) in the river water too. Pollution controls were respectively suggested for these tow types according to different pollution causes.  相似文献   

16.
Fossil footprints are important in understanding Cretaceous avian diversity because they constitute evidence of paleodiversity and paleoecology that is not always apparent from skeletal remains. Early Cretaceous bird tracks have demonstrated the existence of wading birds in East Asia, but some pedal morphotypes, such as zygodactyly, common in modern and earlier Cenozoic birds (Neornithes) were unknown in the Cretaceous. We, herein, discuss the implications of a recently reported, Early Cretaceous (120–110 million years old) trackway of a large, zygodactyl bird from China that predates skeletal evidence of this foot morphology by at least 50 million years and includes the only known fossil zygodactyl footprints. The tracks demonstrate the existence of a Cretaceous bird not currently represented in the body fossil record that occupied a roadrunner (Geococcyx)-like niche, indicating a previously unknown degree of Cretaceous avian morphological and behavioral diversity that presaged later Cenozoic patterns. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Masaki MatsukawaEmail:
  相似文献   

17.
Slow growth in herbivores may lead to higher mortality, due to prolonged exposure to natural enemies. A number of studies has tested the 'slow-growth, high-mortality' hypothesis using predators or parasitoids as natural enemies of the herbivore, but the possible role of pathogens is poorly documented. We provide evidence that phytopathogenic infection of a plant enhances the susceptibility of herbivore larvae to a generalist entomopathogen. Larvae of the mustard leaf beetle Phaedon cochleariae grow more slowly when feeding on Chinese cabbage leaves infected by the phytopathogenic fungus Alternaria brassicae than larvae feeding on healthy leaves. Treatment of such larvae feeding on diseased plants with an LD50 of the entomopathogenic fungus Metarhizium anisopliae resulted in 100% mortality, compared with a mortality rate of 54% in the control larvae feeding on uninfected leaves. This is the first demonstration of an interaction between a phyto- and an entomopathogenic fungus.  相似文献   

18.
Parasites and pathogens often impose significant costs on their hosts. This is particularly true for social organisms, where the genetic structure of groups and the accumulation of contaminated waste facilitate disease transmission. In response, hosts have evolved many mechanisms of defence against parasites. Here we present evidence that Atta colombica, a leaf-cutting ant, may combat Escovopsis, a dangerous parasite of Atta's garden fungus, through a colony-level behavioural response. In A. colombica, garden waste is removed from within the colony and transported to the midden - an external waste dump - where it is processed by a group of midden workers. We found that colonies infected with Escovopsis have higher numbers of workers on the midden, where Escovopsis is deposited. Further, midden workers are highly effective in dispersing newly deposited waste away from the dumping site. Thus, the colony-level task allocation strategies of the Atta superorganism may change in response to the threat of disease to a third, essential party.  相似文献   

19.
研究了溶液中牛血清白蛋白(BSA)的存在对Ni2 与δ-MnO2衡性质的影响.结果表明, BSA存在时Ni2 在δ-MnO2表面的吸附率'pH曲线仍为典型的"S"形, BSA使Ni2 的吸附突跃向高pH方向移动,影响程度与BSA的加入方式及浓度有关,其大小次序为Ⅳ(先加BSA后加Ni2 ),Ⅲ(N2 和BSA同时加)≈Ⅱ(先加Ni26 后加BSA).BSA存在时Ni2 的等温吸附线很好地遵循Langmuir等温吸附方程, Ni2 的饱和吸附量与BSA的加入方式有关,其大小次序为I(不加BSA)>Ⅱ.m,Ⅳ.升高温度促进Ni2 的吸附.在pH:4.0和pH:7.0条件下, Ni2 在δ-MnO2上的吸附均是不可逆的, BSA对Ni2 的吸附可逆性没有影响.  相似文献   

20.
A specimen of the horned dinosaur Psittacosaurus from the early Cretaceous of China is described in which the integument is extraordinarily well-preserved. Most unusual is the presence of long bristle-like structures on the proximal part of tail. We interpret these structures as cylindrical and possibly tubular epidermal structures that were anchored deeply in the skin. They might have been used in display behavior and especially if one assumes that they were colored, they may have had a signal function. At present, there is no convincing evidence which shows these structures to be homologous to the structurally different integumentary filaments of theropod dinosaurs. Independent of their homology, however, the discovery of bristle-like structures in Psittacosaurus is of great evolutionary significance since it shows that the integumentary covering of at least some dinosaurs was much more complex than has ever been previously imagined.  相似文献   

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