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1.
During the last two decades more than twenty phylogenetic analyses of pterosaur relationships have been published. These range from small scale studies restricted to a few species from one clade, to comprehensive analyses that include the majority of known taxa. Most of these contributions can be traced back to data sets published either by Kellner (2003) or Unwin (2003), who, in turn, incorporated data from earlier analyses by Howse and Bennett.  相似文献   

2.
吕君昌 《地球学报》2016,37(2):129-140
在江西赣州地区晚白垩世地层中发现的窃蛋龙类化石——赣州华南龙,属于进步窃蛋龙类,其独特的头部特征为研究窃蛋龙类恐龙的颅面演化、古地理分布及古生态环境提供重要信息;在辽西早白垩世义县组地层中发现的大型、前肢短的驰龙类恐龙——孙氏振元龙,为大型、短前肢类型的驰龙类提供羽毛形态学方面的重要信息,为研究驰龙类的多样性、鸟类羽毛以及飞行起源提供了重要依据;在辽西发现的喙嘴龙类翼龙——朝阳东方颌翼龙,是该地区晚侏罗世地层中发现的第一件翼龙标本,不仅填补了时代上的空白,同时对于印证晚侏罗世喙嘴龙类的辐射演化具有重要作用。这些重要发现对于研究窃蛋龙类的演化、驰龙类羽毛演化及鸟类羽毛起源等热点与难点问题提供了重要的参考依据,尤其在发现华南龙的基础上,命名了赣州恐龙动物群。  相似文献   

3.
达尔文翼龙的发现及其意义   总被引:1,自引:0,他引:1  
吕君昌 《地球学报》2010,31(2):129-136
达尔文翼龙为中等大小的翼龙类, 发现于辽西辽宁省建昌县玲珑塔中侏罗世髫髻山组, 是目前已知唯一由原始类群(非翼手龙类)向进步类群(翼手龙类)演化的过渡类型。它既具有原始类群的特征: 比如尾长, 多于20节尾椎椎体, 且尾椎椎体由极度加长的、纤细的前后关节突及脉弧所包裹, 构成一僵硬的尾部, 第五脚趾具有两个长的趾节; 又具有进步类群的特征: 比如头骨加长, 鼻孔和眶前孔愈合为一大的鼻眶前孔, 颈椎椎体长, 没有或者颈肋退化; 翼掌骨与肱骨的比率介于原始类群和进步类群之间。达尔文翼龙的发现具有重要意义, 它填补了由原始翼龙类向进步翼龙类演化的空白, 为生物宏观演化(模块演化)机制-即组成生物体的模块在短时间内共同演化提供例证。从达尔文翼龙的骨骼结构变化上看, 空中丰富的食物来源(比如飞行能力差的、带羽毛的恐龙、滑翔的哺乳动物、小的翼龙及昆虫等), 可能为导致翼龙头骨和颈部首先演化的原因之一。达尔文翼龙的发现, 有可能打破对翼龙类传统分为两大类的方法。  相似文献   

4.
根据发现于中国辽西九佛堂组一几乎完整的成年中国翼龙的头后骨架,对中国翼龙的鉴定特征进行了修订。翼龙的修正特征包括头骨相对长且具有不发育的头骨嵴;一些肢骨元素之间的生长比率不变,比如第二翼指骨与第一翼指骨的长度之比率为0.73;翼掌骨与第三跖骨长度之比率为4.5;第三跖骨与胫骨的长度之比率约0.21,以及第一和第二翼指骨骨干直。通过对中国翼龙的非成年个体和成年个体肢骨元素比率的比较,显示在生长发育过程中,一些肢骨之间生长比率是不变的,比如第一和第二翼指骨之间,翼掌骨和第三跖骨之间,第三跖骨与胫骨之间;而另一些则不同,比如肱骨比翼掌骨生长得快,及股骨也比胫骨都生长得快。中国辽西早白垩世九佛堂组中国翼龙(爬行动物纲:翼龙目)新材料@吕君昌$中国地质科学院地质研究所!北京,100037 @刘金远$大连自然博物馆!116023 @王旭日$大连自然博物馆!116023 @高春玲$大连自然博物馆!116023 @孟庆金$大连自然博物馆!116023 @季强$中国地质科学院地质研究所!北京,100037  相似文献   

5.
本文总结了古神翼龙类的特征,尤其是对中国发现的没有牙齿的翼龙类(包括古神翼龙类、朝阳翼龙类及神龙翼龙类)进行系统总结。通过对比,把中国的古神翼龙类建立两个新的亚科:中国翼龙亚科及华夏翼龙亚科。从古神翼龙类头骨形态变化来看,其演化趋势是头骨由低长向短高变化,这一变化的原因可能与其食性变化有关。根据在辽西凌源四合当九佛堂组发现的一几乎完整的化石骨架建立了中国翼龙新种:凌源中国翼龙(新种),它具有以下特征:鼻眶前孔的长度与高度之比率为3.20;吻部指数为3.03;股骨与胫骨长度之比率约为0.66以及第2翼指骨与第1翼指骨长度之比率为0.85。根据发现于辽西朝阳九佛堂组的另一个体较小的古神翼龙类化石骨架,建立华夏翼龙属一新种:返祖华夏翼龙(新种)。虽然它个体较小,但是它具有华夏翼龙类似的头骨脊,然而它的第2和第3翼指骨的后面具有原始喙嘴龙类翼龙的沟状结构,以区别于其它的华夏翼龙类。返祖华夏翼龙的翼指骨后部沟状结构的出现,应为返祖现象的体现。而这一现象,在翼手龙类中为首次报道。  相似文献   

6.
Pterosaurs exhibit a large size range with the smallest approximately the size of a sparrow and the largest about the size of a small airplane. Based on studies of extant flying vertebrates and principles of allometry (Norberg & Rayner, 1987; Rayner, 1988), a reasonable assumption is that pterosaurs of different sizes used their wings differently during flight.  相似文献   

7.
The anatomical term tuba vertebralis was introduced by Martill et al. (1998) to describe a bony tube which enclosed the spinal cord in the type cervical vertebra of the giant azhdarchid pterosaur Arambourgiania philadelphiae, from the Late Cretaceous of Jordan.  相似文献   

8.
吕君昌 《地球学报》2010,31(Z1):49-51
本文回顾了中国翼龙化石的发现和研究。特别是最近几年在辽宁省西部及其周边地区发现的大量的翼龙化石,使该地区成为世界上最著名的翼龙化石产地之一,尤其是对研究陆相沉积中的翼龙,物种分异和古生物学的重要性可以与德国的Solnhofen Limestone和巴西的Santana Formation 相媲美。目前中国发现有隶属12个科的34个属的翼龙。既包括原始的喙嘴龙类,进步的翼手龙类,也包括处于两者之间的过渡类型-达尔文翼龙类以及胚胎蛋化石。  相似文献   

9.
Colin PALMER 《地球学报》2010,31(Z1):53-53
The wing of a pterosaur is unique in many ways, not least in its basic morphology, comprising a single supporting structure along the anterior edge of a flexible membrane lifting surface. No other flying vertebrate has adopted this morphology and there are no direct analogues in mechanical aerodynamics, the closest being sailboat mainsails.  相似文献   

10.
Pterosaur diversity in China has increased tremendously in the last two decades particularly due to discoveries made in deposits of western Liaoning. Most species belong to the Pterodactyloidea, a clade that groups the more derived members of the Pterosauria, but recently the number of non-pterodactyloid taxa has grown (e.g., Czerkas & Ji 2002, Lü, 2009).  相似文献   

11.
Résumé De travaux menés dans les zones littorales de l'Afrique du Nord et dans tout le S de l'Espagne, l'auteur tire une nouvelle définition des grands ensembles structuraux péri-méditerranéens. Ces ensembles sont, dans les Cordillères bétiques, du N au S: zones externes (Prébétique, Subbétiques, Pénibétiques), zones internes (Flyschs gaditans, Malaguides, Alpujarrides, Nevadides 1). Dans le Rif marocain, symétriquement, on rencontre du S au N: zones externes (Autochtone de l'Atlas, nappes prérifaines et intrarifaines), zones internes (Flyschs nord-rifains, Tétouanides 2), Ghomarides 3), Sebtides 4); la plupart de ces zones se poursuivent vers l'E, jusqu'en Tunisie et en Sicile.Le fait majeur, à souligner au départ, est la parfaite symétrie de la chaîne alpine de la Méditerranée occidentale: les nappes rifaines ne le cèdent pas en importance aux nappes bétiques. Les diverses unités des deux systèmes se raccordent de manière évidente par la courbure de Gibraltar. L'âge du paroxysme tectonique paraît entièrement compris entre Oligocène supérieur et Miocène supérieur, aucune preuve objective n'existant de nappes plus anciennes.La remise en place des divers ensembles structuraux dépend de l'hypothèse générale définie au départ. Il est d'abord fait allusion à l'interprétation classique, par charriages modérés, ne faisant pas appel à des modifications importantes dans l'emplacement des bassins sédimentaires, actuellement visibles en plan. Les objections à ce premier schéma paraissent déterminantes.Une deuxième interprétation, que l'auteur a déjà partiellement esquissée auparavant, sera envisagée: les unités externes (s'empilant sur elles-mêmes) et leurs socles s'enfonceraient sous les zones internes qui, par réaction, seraient poussées vers l'extérieur de la chaîne: chacune des nappes dépasserait la nappe plus basse, au cours de ce mouvement. Dans le cas de l'Espagne, avant les charriages, les domaines sédimentaires des zones internes se placeraient à l'inverse de la disposition actuelle, soit du N au S: Nevadides, Alpujarrides, Malaguides, Pénibétique et Flyschs gaditans (ultras). Du côté marocain, nous aurions de même du S au N: Sebtides, Ghomarides, Tétouanides, Flyschs nord-rifains (ultras). Cela obligerait, au total, à faire rapprocher l'un de l'autre, en profondeur, les bâtis de la Meseta ibérique et de l'Atlas marocain, d'environ 300 à 500 km, l'actuelle largeur de la mer d'Alboran (150 km) ne permettant pas de reloger les domaines de toutes les nappes. Un axe d'enfouissement serait à rechercher sous l'actuelle Méditerranée.Une troisième interprétation, proposée aujourd'hui par l'auteur, considère que la chaîne péri-méditerranéenne montre une cicatrice structurale fondamentale, qui séparerait domaines internes bétiques et rifains, d'une part, domaines bétiques et rifains plus externes, de l'autre. Cette cicatrice se couderait au niveau de Gibraltar. Les nappes internes seraient comme aspirées vers la cicatrice ainsi que, en sens inverse, les nappes externes. La reconstitution paléogéographique finale est fort satisfaisante et l'ampleur des rétrécissements sensiblement diminuée.La position du domaine des Flyschs kabyles, nord-rifains et gaditans, fait enfin l'objet d'un examen nouveau: sans rejeter l'origine ultra, déjà proposée, l'auteur envisage d'autres solutions, qui auraient l'avantage de mieux s'intégrer dans l'image proposée aujourd'hui.  相似文献   

12.
Petrogenetic grids in the system NCKFMASH (Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O)and the subsystems NCKMASH and NCKFASH calculated with the softwareTHERMOCALC 3.1 are presented for the PT range 7–30kbar and 450–680°C, for assemblages involving garnet,chloritoid, biotite, carpholite, talc, chlorite, kyanite, staurolite,paragonite, glaucophane, jadeite, omphacite, diopsidic pyroxene,plagioclase, zoisite and lawsonite, with phengite, quartz/coesiteand H2O in excess. These grids, together with calculated compatibilitydiagrams and PT and TXCa and PXCa pseudosectionsfor different bulk-rock compositions, show that incorporationof Ca into the NKFMASH system leads to many of the NKFMASH invariantequilibria moving to lower pressure and/or lower temperature,which results, in most cases, in the stability of jadeite andgarnet being enlarged, but in the reduction of stability ofglaucophane, plagioclase and AFM phases. The effect of Ca onthe stability of paragonite is dependent on mineral assemblageat different PT conditions. The calculated NCKFMASH diagramsare powerful in delineating the phase equilibria and PTconditions of natural pelitic assemblages. Moreover, contoursof the calculated phengite Si isopleths in PT and PXCapseudosections confirm that phengite barometry in NCKFMASH isstrongly dependent on mineral assemblage. KEY WORDS: phase relations; metapelites; NCKFMASH; THERMOCALC; phengite geobarometry  相似文献   

13.
A series of high temperature experiments was undertaken to study partitioning of several highly siderophile elements (HSE; Ru, Rh, Pd, Re, Os, Ir, Pt and Au) between Cr-rich spinel, olivine, pyroxene and silicate melt. Runs were carried out on a Hawaiian ankaramite, a synthetic eucrite basalt, and a DiAn eutectic melt, at one bar, 19 kbar, and 20 kbar, respectively, in the temperature range of 1200 to 1300°C, at oxygen fugacities between the nickel-nickel oxide (NNO) and hematite-magnetite (HM) oxygen buffers. High oxygen fugacities were used to suppress the formation of HSE-rich “nuggets” in the silicate melts. The resulting oxide and silicate crystals (<100 μm) were analyzed using both SIMS and LA-ICP-MS, with a spatial resolution of 15 to 50 μm. Rhenium, Au and Pd were all found to be incompatible in Cr-rich spinel (DResp/melt = 0.0012-0.21, DAusp/melt = 0.076, DPdsp/melt = 0.14), whereas Rh, Ru and Ir were all found to be highly compatible (DRhsp/melt = 41-530, DRusp/melt = 76-1143, DIrsp/melt = 5-22000). Rhenium, Pd, Au and Ru were all found to be incompatible in olivine (DReoliv/melt = 0.017-0.073, DPdoliv/melt = 0.12, DAuoliv/melt = 0.12, DRuoliv/melt = 0.23), Re is incompatible in orthopyroxene and clinopyroxene (DReopx/melt = 0.013, DRecpx/melt = 0.18-0.21), and Pt is compatible in clinopyroxene (DPtcpx/melt = 1.5). The results are compared to and combined with previous work on HSE partitioning among spinel-structured oxides, and applied to some natural magmatic suites to demonstrate consistency.  相似文献   

14.
Résumé On peut, en résumé, caractériser ainsi les principales provinces de la Bulgarie: — les Rhodopes constituent une zone typiquement polymétallique avec une prépondérance soulignée de Pb, Zn; le F, Cr, Ni, y existent en quantité subordonnée; en traces viennent encore: le Ba, Mn, Cd, Sb, W, Mo, Bi, As, Au, Ag, V; — la Sredna Gora est caractérisée comme une zone de cuivre typique, avec la présence de Fe, Mn, et en quantitée subordonnée de Pb, Zn, Mo, Ti, V, Au. — les Balkans portent les particularités d'une zone polymétallique (Pb, Zn, Cu) avec fer. On y remarque souvent des gîtes individualisés de cuivre, polymétallique avec fer, argent, ainsi que des gîtes complexes. Le Mn, Ba, Au, Ag, Co, Mo, As, Hg, V, W viennent en quantité subordonnée; — la zone des Kraistides, analogue à la précédente, se caractérise par des gisements polymétalliques pauvres et des gîtes à or et scheelite. Les éléments principaux sont: Au, Ba et secondaires: Pb, Zn, Cu, V et en partie du Fe et Hg; — la plateforme mésique, outre le gaz, se caractérise par le manganèse de la dépression de Varna.
The metallogenic map of Bulgaria displays the following four major and distinct provinces: The Rhodopes as a typically polymetallic zone, mainly with Pb and Zn, but also with F, Cr and Ni, and minor or trace amounts of Ba, Mn, Cd, Sb, Mo, Bi, As, Au, Ag, V. The Sredna-gora is a distinct copper zone, with Fe and Mn, and minor amounts of Pb, Zn, Mo, Ti, V, Au. The Balkan is again a polymetallic zone of Pb, Zn and Cu with Fe; but Cu-Fe-Ag-deposits also occur. The other elements are present in minor quantities only. The Kraiste-Zone resembles the previous one and contains low grade polymetallic and scheelite deposits. The main elements are Au, Ba, and minor quantities of Pb, Zn, Cu, V and in part Fe and Hg. The zone of the Mésie platform contains only the manganese deposits of the Varna depression, in addition to natural gas.
  相似文献   

15.
The Cu–Co–Ni Texeo mine has been the most important source of Cu in NW Spain since Roman times and now, approximately 40,000 m3 of wastes from mine and metallurgical operations, containing average concentrations of 9,263 mg kg−1 Cu, 1,100 mg kg−1 As, 549 mg kg−1 Co, and 840 mg kg−1 Ni, remain on-site. Since the cessation of the activity, the abandoned works, facilities and waste piles have been posing a threat to the environment, derived from the release of toxic elements. In order to assess the potential environmental pollution caused by the mining operations, a sequential sampling strategy was undertaken in wastes, soil, surface and groundwater, and sediments. First, screening field tools were used to identify hotspots, before defining formal sampling strategies; so, in the areas where anomalies were detected in a first sampling stage, a second detailed sampling campaign was undertaken. Metal concentrations in the soils are highly above the local background, reaching up to 9,921 mg kg−1 Cu, 1,373 mg kg−1 As, 685 mg kg−1 Co, and 1,040 mg kg−1 Ni, among others. Copper concentrations downstream of the mine works reach values up to 1,869 μg l−1 and 240 mg kg−1 in surface water and stream sediments, respectively. Computer-based risk assessment for the site gives a carcinogenic risk associated with the presence of As in surface waters and soils, and a health risk for long exposures; so, trigger levels of these elements are high enough to warrant further investigation.  相似文献   

16.
The nine elastic constants of andalusite and sillimanite have been determined, using the technique of Brillouin scattering. They are, in megabars, for andalusite: c 11=2.334, c 22=2.890, c 33=3.801, c 44=0.995, c 55=0.878, c 66=1.123, c 23=0.977, c 13=1.162, c 12=0.814; for sillimanite: c 11=2.873, c 22=2.319, c 33=3.884, c 44=1.224, c 55=0.807, c 66=0.893, c 23=1.586, c 13=0.834, c 12=0.947. Both structures are characterized by chains of edge-linked coordination octahedra extending parallel to the crystallographic c direction, cross-linked by polyhedra of lower coordination. In each structure the stiffness measured parallel to c is greater than that measured normal to c. The shear moduli can be directly correlated with the relative rigidity of the cross-linking structures.  相似文献   

17.
Present study addresses the role of major plate-driving forces, particularly the slab pull and slab resistive forces, for the generation of 26 December 2004 M w > 9.0 off Sumatra megathrust earthquake. Major controls on the plate-driving forces are normally visualized through age, speed, and average dip of the slab during subduction. Wide variation in age, plate obliquity, stress obliquity, subduction rate, dip angle, and flexing depth of the subducting oceanic lithosphere between Andaman and Sumatra thus allowed us for quantitative evaluation of the slab pull (F SP) and slab resistive (F SR) forces in three well-defined sectors (I, II and III). Computed values of these forces in the three sectors: (1) F SP = 1.29 × 1013 N/m, F SR = 1.41 × 1013 N/m; sector I, (2) F SP = 2.10 × 1013 N/m, F SR = 1.13 × 1013 N/m; sector II, and (3) F SP = 2.08 × 1013 N/m, F SR = 2.72 × 1013 N/m; sector III clearly suggest a spatial variation of stress regime in the subducting oceanic lithosphere. Excess F SR in sectors I and III are interpreted as the causative forces behind the triggering of major seismic energy bursts near Sumatra and Andaman on 26 December 2004. A gap of minimum seismic energy burst near Great Nicobar possibly was controlled by the excess of F SP in sector II. This study further advocates that the cyclic stress, resulted from unbalanced component of slab resistive force, had a definite control on the occurrence of 2004 off Sumatra megathrust earthquake around the flexing zone of the subducting lithosphere.  相似文献   

18.
Analysis of external stability of vertical geosynthetic-reinforced soil (GRS) walls is very important in the seismic prone zone. The scope of this paper is to obtain required minimum reinforcement length, L min, for external seismic stability of vertical GRS walls by pseudo-static limit equilibrium method. Then, L min can be calculated to resist sliding, eccentricity, and bearing capacity failure modes. The parameters considered include both horizontal and vertical seismic coefficients (k h and k v ), surcharge load (q), wall height (H) and the properties of retained backfill, GRS, and foundation soil. Results show that L min against sliding failure mode, L min,S , increases more quickly than that against the other two failure modes with the increase in k h , q, or unit weight of retained backfill, γ b , while L min,S decreases more quickly than that against the other two failure modes with increase in friction angle of retained backfill, ? b , or unit weight of GRS, γ r . For the different failure modes, the effect of k v on L min is not identical with the change of k h , and in addition, L min/H will tend to remain unchanged with the increase in H. In general, L min against bearing capacity failure mode, L min,BC, is larger than L min against the other two failure modes. However, L min,BC will be less than L min against eccentricity failure mode, L min,E , for k h exceeding 0.35, or friction angle of foundation soil, ? f , exceeding 37°, and L min,BC will also be less than L min,S for friction angle of GRS, ? r , being no more than 26°.  相似文献   

19.
Summary The crystal structure of arsentsumebite, ideally, Pb2Cu[(As, S)O4]2(OH), monoclinic, space group P21/m, a = 7.804(8), b = 5.890(6), c = 8.964(8) ?, β = 112.29(6)°, V = 381.2 ?3, Z = 2, dcalc. = 6.481 has been refined to R = 0.053 for 898 unique reflections with I> 2σ(I). Arsentsumebite belongs to the brackebuschite group of lead minerals with the general formula Pb2 Me(XO4)2(Z) where Me = Cu2+, Mn2+, Zn2+, Fe2+, Fe3+; X = S, Cr, V, As, P; Z = OH, H2O. Members of this group include tsumebite, Pb2Cu(SO4)(PO4)(OH), vauquelinite, Pb2Cu(CrO4)(PO4)(OH), brackebuschite, Pb2 (Mn, Fe)(VO4)2(OH), arsenbracke buschite, Pb2(Fe, Zn)(AsO4)2(OH, H2O), fornacite, Pb2Cu(AsO4)(CrO4)(OH), and feinglosite, Pb2(Zn, Fe)[(As, S)O4]2(H2O). Arsentsumebite and all other group members contain M = MT chains where M = M means edge-sharing between MO6 octahedra and MT represents corner sharing between octahedra and XO4 tetrahedra. A structural relationship exists to tsumcorite, Pb(Zn, Fe)2(AsO4)2 (OH, H2O)2 and tsumcorite-group minerals Me(1)Me(2)2(XO4)2(OH, H2O)2. Received June 24, 2000; revised version accepted February 8, 2001  相似文献   

20.
The supposedly second finding of rare arsenosilicate cervandonite-(Ce) in the world is characterized. The mineral was recognized in the ore-bearing metasomatic rocks of the Berezitovoe gold-base metal deposit (Upper Priamurye, Russian Far East) in association with quartz, biotite, muscovite, orthoclase, garnet (almandine-spessartine), tourmaline, basic plagioclase, and sulfides. The cervandonite is represented by optically homogeneous and heterogeneous aggregates with visible crystals from 10 fum to 0.1–0.3 mm in size. Based on the microprobe analysis, the average chemical composition of the homogeneous cervandonite-(Ce) aggregates is as follows (wt %): Ce2O3 - 13.00, La2O3 - 5.70, Nd2O3 - 5.20, Pr2O3 - 1.41, Y2O3 - 0.77, Sm2O3 - 0.77, Eu2O3 - 0.23, Gd2O3 - 0.54, Dy2O3 - 0.31, ThO2 - 1.12, UO2 - 0.30, TiO2 - 12.86, Al2O3 - 9.24, Fe2O3 - 8.93, FeO - 2.68, CaO - 0.14, SiO2 - 19.98, As2O3 - 16.19. The comparative study of the cervandonite-(Ce) from the Berezitovoe deposit and the analogous minerals from the Alpine mica gneiss of Mt. Pizzo Cervandone (Central Alps) showed that the former mineral can be assigned to a new variety of cervandonite-(Ce) in terms of its compositional features. This variety is characterized by an ordered stoichiometric composition corresponding to the simpler theoretical formula (Ce,Nd,La)(Fe3+, Fe2+, Ti4+, Al)3 (Si2As3+)3O12.  相似文献   

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