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31.
1932年12月25日,我国甘肃省西部玉门镇以南的昌马地区发生了7.6级地震。震中区产生了规模较大的地面破裂带,其中有张性、压性和剪切等多种型式裂缝。本文根据分析各种自然破坏现象的形成条件,结合极震区地质构造特征,对震源区的应力作用和地震成因提出初步看法。 对地震破裂带的分析结果表明,这次地震起主要作用的是南北向的水平挤压作用,并与自白垩纪以来控制着本区构造断裂的区域应力场是一致的。地震破裂带出现的部位与长期活动的昌马构造断裂带一致。因此,我们认为昌马地震的发生是昌马构造断裂带继承性活动的结果。 相似文献
32.
Since Holcorpa maculosa was first described in 1878, it has attracted lots of attention due to its extremely elongate abdominal segments from the sixth to the eighth. Fossil records of family Holcorpidae are very rare, comprising two species in one genus represented by three fossil specimens, resulting in limited knowledge on the structure and function of holcorpid’s unique male organ, as well as its evolutionary relationship with other scorpionflies. Herein we describe a new genus with a new species, Conicholcorpa stigmosa gen. et sp. nov., of the Holcorpidae from the Middle Jurassic Jiulongshan Formation near Daohugou Village, Inner Mongolia, China. This is the first holcorpid documented from the Daohugou locality, albeit two previously reported species with extremely elongate male organs but deemed as Family Incertae sedis. C. stigmosa gen. et sp. nov. is the earliest holcorpid hitherto, extending its existence from the Early Eocene to the Middle Jurassic by 114 million years and providing one more early case of presenting exaggerated male body parts for sexual display and/or selection. Our analysis supports the sister relationship between Holcorpidae and Orthophlebiidae. Our results not only enhance our knowledge of the morphology of Holcorpidae but also elucidate the relationship of known species of this family. 相似文献
33.
正Objective Symphyta,as an ancestral and paraphyletic group,are mainly phytophagous lineages.In order to truly elucidate their natural history and the development trends,we need to cover more species,including the extinct and extant species.In general,fossils sometimes appear to be necessary since extinct species usually have the so-called transitional states,which play important roles in their early evolution.It is well known that the Early Cretaceous 相似文献
34.
New Mesozoic Mesopsychidae(Mecoptera)from Northeastern China 总被引：2，自引：2，他引：0
<正>The Mesozoic family Mesopsychidae Tillyard,1917 presently consists of seven described genera and 13 species from the mid-Triassic to the Early Cretaceous of Australia,South Africa and Eurasia.In the present paper one new genus and three new species of fossil mesopsychids are described that add significant distributional and stratigraphic extensions to the family.This finding documents the first formal record of fossil Mesopsychidae in China.Both Lichnomesopsyche gloriae gen.et sp.nov.and L.daohugouensis gen.et sp.nov. were found from the Middle Jurassic Jiulongshan Formation of Inner Mongolia,whereas Vitimopsyche kozlovi sp. nov.,of mid Early Cretaceous age,was collected from the Jehol Biota of northern Hebei Province.This new,well-preserved material from China reveals complete and previously unknown body features,including head, antennae,mouthparts,legs and abdomen.The delicate and long proboscides of these new taxa indicate that they were feeding on externally exposed,nutrient-rich fluids of gymnospermous ovulate fructifications,and incapable of piercing surface epidermis-attributable principally to the absence of stylets.These proboscides originated, perhaps multiply,among basal Mecoptera and are functionally and structurally convergent with equivalent mouthparts borne by fossil and extant Diptera,Lepidoptera,Neuroptera and Coleoptera. 相似文献
35.
In this paper,three approachs were developed to find indicator species from the habitat created by coastal structures.These approachs consist of a model of species co-occurrence probability,a model of k-environmental factor probability and a composite model.Simultaneously,a case study was conducted in Hsinchu Fishing Port of north-western Taiwan.Based on the aforementioned models,three primary producer species,Ahnfeltiopsis flabelliformis,Chondrus ocellatus and Sarcodia montagneana,were chosen as the indicator species which had the highest co-occurrence probabilities and showed greater tolerance to more critical environment.It is imperative to understand how the three species under particular co-occurring conditions and environmental factors influence the composition of sessile assemblages in coastal water.The results indicate that for the purpose of increasing biodiversity,these models are feasible to find indicator species of artificial structures,and to help make it possible to design coastal structures based on biological considerations.This study provides an innovative approach for further advanced application in the artificial habitat of coast management. 相似文献