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Mesozoic deposits of the former Gondwanaland are depauperate in early mammals, in general, and multituberculate mammals, in particular. Until now, the oldest multituberculate mammals known from the Gondwanan continents come from the Early Cretaceous of Morocco, NW Africa. Here, we report the presence of a new multituberculate mammal, Indobaatar zofiae gen. et sp. nov., from the Lower/Middle Jurassic Kota Formation, Pranhita-Godavari valley in peninsular India. This is the first record of a multituberculate from the Mesozoic rocks of India and possibly predates the oldest known multituberculates from Gondwanan continents. The new specimen, representing an upper premolar (P4), compares well with the upper premolar morphology of Eobaatariinae multituberculates known from the Early Cretaceous of Mongolia, China, England, and Spain. Together with the recent findings of cimolodontan multituberculates from the Early Cretaceous of Australia and Late Cretaceous of South America, the new discovery indicates a wide temporal and spatial distribution for multituberculate mammals in the former Gondwanaland. 相似文献
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Cavin L 《Die Naturwissenschaften》2010,97(12):1035-1040
Gars (Lepisosteidae) are ray-finned fishes with controversial relationships to other actinopterygian lineages. When fossil
taxa are considered, gars are grouped with Mesozoic macrosemiids and ‘semionotids’ in the Semionotiformes, but the intra-relationships
within this order are still elusive. Here, the evolutionary history of gars is reinvestigated using a set of well-preserved
extinct semionotiform taxa in a phylogenetic analysis. Results indicate that the gar lineage roots in a clade of Late Jurassic–Cretaceous
semionotiform fishes. The closest relatives to gars were plant-eating and detritivorous freshwater fishes. The occurrence
of semionotiform remains in Early and early Late Cretaceous continental deposits worldwide possibly reflects an important
radiation of this group, comparable to the present-day diversification of cypriniforms. Other Late Triassic to Early Cretaceous
semionotiform taxa are gathered in a single clade with weakly supported internal nodes, pointing out the necessity to better
understand the osteology of these fishes. 相似文献
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The Basque country magnetic anomaly follows a NW-SE trend over the Basque country (northern Spain) with intensities up to
250 nT measured at 3000 m above sea level. The paired negative part of the anomaly is located to the north and presents intensities
down to −60 nT. A model of the magnetic properties of the crust in the area, taking into account previous geological and geophysical
data, indicates a wedge of material with a magnetic susceptibility of 0.07 SI emplaced along a NE-directed basal thrust. The
anomalous wedge is composed of basic and/or ultrabasic Cretaceous intrusives and lower crustal rocks, and reaches a minimum
depth which increases towards the northwest from 5–7 to 12 km. According to previous works, geological features of the rocks
on top of the anomalous wedge indicate that during the Cretaceous this zone constituted a deep marine environment which underwent
important crustal thinning related to rifting. The transition towards the southwest was to a normal continental platform.
Alpine deformation gave rise to displacement on a basal thrust, which can be correlated with the lower contact of the magnetic
wedge, and emplacement of this wedge towards the northeast. The southeastern termination of the anomaly can be related to
the lateral termination of the basic rocks which constitute the anomalous wedge in a transform fault related to the rifting
event. 相似文献
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Daniel Chure Brooks B. Britt John A. Whitlock Jeffrey A. Wilson 《Die Naturwissenschaften》2010,97(4):379-391
Sauropod dinosaur bones are common in Mesozoic terrestrial sediments, but sauropod skulls are exceedingly rare—cranial materials
are known for less than one third of sauropod genera and even fewer are known from complete skulls. Here we describe the first
complete sauropod skull from the Cretaceous of the Americas, Abydosaurus mcintoshi, n. gen., n. sp., known from 104.46 ± 0.95 Ma (megannum) sediments from Dinosaur National Monument, USA. Abydosaurus shares close ancestry with Brachiosaurus, which appeared in the fossil record ca. 45 million years earlier and had substantially broader teeth. A survey of tooth
shape in sauropodomorphs demonstrates that sauropods evolved broad crowns during the Early Jurassic but did not evolve narrow
crowns until the Late Jurassic, when they occupied their greatest range of crown breadths. During the Cretaceous, brachiosaurids
and other lineages independently underwent a marked diminution in tooth breadth, and before the latest Cretaceous broad-crowned
sauropods were extinct on all continental landmasses. Differential survival and diversification of narrow-crowned sauropods
in the Late Cretaceous appears to be a directed trend that was not correlated with changes in plant diversity or abundance,
but may signal a shift towards elevated tooth replacement rates and high-wear dentition. Sauropods lacked many of the complex
herbivorous adaptations present within contemporaneous ornithischian herbivores, such as beaks, cheeks, kinesis, and heterodonty.
The spartan design of sauropod skulls may be related to their remarkably small size—sauropod skulls account for only 1/200th
of total body volume compared to 1/30th body volume in ornithopod dinosaurs. 相似文献
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The Aravalli mountain range (AMR) in the northwestern part of the Indian Peninsula consists of two main Proterozoic metasedimentary and metaigneous sequences, the Aravalli and Delhi Supergroups, respectively, which rest over the Archaean gneissic basement. A synthesis and reinterpretation of the available geological, geochronological and geophysical data, including results of own field work and geophysical interpretations pertaining to the AMR, indicate its origin as an inverted basin: rifting into granitoid basement began ca. 2.5; Ga ago with Aravalli passive rifting (ca. 2.5–2.0 Ga) and Delhi active rifting (ca. 1.9–1.6 Ga). Associated mafic igneous rocks show both continental and oceanic tholeiitic geochemistry and are comparable with Phanerozoic, rift-related magmatic products. Available data showed no conclusive evidence for oceanic lithoshere and island-arc/active margin magmatic activity in the AMR. Subsequent inversion and orogeny (Delhi orogeny, ca. 1.5-1.4 Ga) lead to complex deformation and metamorphism. Only in the western and central zones has the basement been involved in this mid-Proterozoic (Delhi) deformation, whereas it is unaffected in the eastern part, except for local shear zones mainly along the basement/cover interface. The grade of metamorphism increases from the greenschist facies in the east to the amphibolite facies in the west with local HP assemblages. These latter are explained by rapid burial and exhumation of thin and cool continental lithosphere. Subsequently, during a final, mild phase of inversion, the Vindhyan basins consisting mainly of sandstones, limestones and shales, flanking the AMR formed which are comparable to foreland basins. The tectonic evolution of the AMR is therefore interpreted as an example of a major inverted continental rift and of a Proterozoic intra-continental orogen. 相似文献
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Two mammalian hairs have been found in association with an empty puparium in a ∼100-million-year-old amber (Early Cretaceous)
from France. Although hair is known to be an ancestral, ubiquitous feature in the crown Mammalia, the structure of Mesozoic
hair has never been described. In contrast to fur and hair of some Jurassic and Cretaceous mammals preserved as carbonized
filaments, the exceptional preservation of the fossils described here allows for the study of the cuticular structure. Results
show the oldest direct evidence of hair with a modern scale pattern. This discovery implies that the morphology of hair cuticula
may have remained unchanged throughout most of mammalian evolution. The association of these hairs with a possible fly puparium
provides paleoecological information and indicates peculiar taphonomic conditions. 相似文献
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We report on a new Mesozoic bird, Longirostravis hani, from the Early Cretaceous Jehol Biota of northeastern China. The new taxon has a long, slender rostrum and mandible, and a small number of rostralmost teeth. Postcranial characters such as a furcular ramus wider ventrally than dorsally, a centrally concave proximal margin of the humeral head, and a minor metacarpal that projects distally more than the major metacarpal, support the placement of Longirostravis within euenantiornithine Enantiornithes, the most diverse clade of Mesozoic birds. The morphology of the skull, however, suggests that Longirostravis had a probing feeding behavior, a specialization previously unknown for Enantiornithes. Indeed, this discovery provides the first evidence in support of the existence of such a foraging behavior among basal lineages of Mesozoic birds. 相似文献
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福建古生界至中生界部分地层古地磁研究认为,华南地块的主体部分首先于中奥陶世时期即已拼合,作为一个整体由南纬23.8°向北移动,二叠纪之后越过赤道,继续北移,直至侏罗纪末到达北纬19.6°的位置.而华南地块同扬子地块的拼合是在加里东末期开始的,至少可以认为是在早石炭纪之前两地块就靠近了。这一时期,华南地块和扬子地块的地质构造运动十分活跃. 相似文献
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A. Henk 《Geologische Rundschau》1995,84(3):578-590
Thermal modeling techniques constrained by published petrological and thermo-chronometric data were applied to examine late orogenic burial and exhumation at a Variscan suture zone in Central Europe. The suture separates the southern Rhenohercynian zone from the Mid-German Crystalline Rise and traces the former site of a small oceanic basin. Closure of this basin during Variscan subduction and subsequent collision of continental units were responsible for different tectono-metamorphic evolutions in the suture's footwall and hanging wall. Relative convergence rates between the southern Rhenohercynian zone and western Mid-German Crystalline Rise can be inferred from the pressure-temperature-time evolution of the Northern Phyllite Zone. During Late Viséan-Early Namurian times, horizontal thrusting velocities were at least 20 mm/a. Thermal modeling suggests that exhumation of the Mid-German Crystalline Rise occurred temporarily at rates of more than 3 mm/a. Such rapid exhumation cannot be produced by erosion only, but requires a substantial contribution of extensional strain. Exhumation by upper crustal extension occurred contemporaneously with convergence and is explained by continuous underplating of crustal slices and thrusting along faults with ramp-flat geometry. Finally, implications for the tectono-metamorphic history of the study area and the thermal state of the crust during late Variscan exhumation are discussed. 相似文献
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藏北唐古拉坳陷中央隆起带与北部凹陷带海相体罗-白垩纪地层中,夹杂一套以高钾安山岩、高铝玄武岩为主体的高钾钙碱性火山岩系列。主要岩石类型有玄武岩、高铝玄武岩、高钾安山岩、英安岩、流纹岩及流纹质角砾凝灰岩。根据火山岩产出特征和全岩同位素年龄测定,将本区火山活动划分为中生代晚期和老第三纪两个旋回。这套火山岩系的REE、相容元素和不相容元素分布特点与造山带火山岩类似;在构造判别图解上,其投影点均落在造山带大山岩区域内。对火山岩特征分析表明,它们的形成与俯冲作用有关,显示出在俯冲造山带的构造背景下演变而来。 相似文献
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Sixty five per cent of the Paleozoic basement of western and central Europe is hidden by a sedimentary cover and/or sea. This work aims to remove that blanket to detect new structures which could used to build a more comprehensive model of the Variscan orogeny. It is based on the interpretation of various forms of data: (a) published gravity maps corrected for the effects of the crust–mantle boundary topography and light sedimentary basins; (b) aeromagnetic maps; (c) measurements of densities; and (d) induced and remanent magnetizations on rocks from Paleozoic outcrops of the upper Rhenish area. From the northern Bohemian Massif to the eastern Paris Basin, the Saxothuringian is characterized by a 500?km long belt of gravity highs, the most important being the Kraichgau high. Most of the corresponding heavy bodies are buried under a post-early Viséan cover. They are interpreted as relics of Late Proterozoic terranes overlain by an Early to Middle Paleozoic sequence, equivalent to the Bohemian terrane in the Bohemian Massif. The most probable continuation of these dense Bohemian terranes toward the west is the Southern Channel–Northern Brittany Cadomian terrane. The gravity lows are correlated with Variscan granites and pre- and early Variscan metagranites. Gravity and magnetic maps demonstrate large-scale displacement in Devonian–Early Carboniferous times along the parallel and equidistant, NW–SE striking, Vistula, Elbe, Bavarian, Bray and South Armorican dextral wrench faults. In the Vosges–Schwarzwald and Central Massif the faults continue with the east–west striking Lalaye-Lubine–Baden-Baden and Marche faults and with south vergent thrusts. The Bavarian faults shift the Kraichgau terrane by 150?km relative to the Bohemian terrane, whereas the offset of the Northern Brittany Cadomian relative to the Northern Vosges–Kraichgau terranes is estimated at 400?km along the Bray fault. Sinistral wrench faults are the NE–SW striking Sillon Houiller, Rheingraben, Rodl, Vitis and Diendorf faults. The southern Vosges–Schwarzwald Devonian–Dinantian basin is interpreted as a pull-apart basin at the south-easterly extremity of the Bray fault. The Bohemian and Kraichgau body form allochthonous terranes which were thrust over the Saxothuringian crust. Thrusting to the north-west was accompanied by back-thrusting and led to the formation of pop-up structures. Contemporaneous dextral and sinistral wrench faulting resulted in transpressive strain during collision. The zonal structure of the Variscides in the sense of Kossmat (1927) is relevant only to the Rhenohercynian Foreland Belt. Kossmat (1927) already spoke of a Moldanubian Region because it displays no real zonal structure. The Saxothuringian Zone was formed by terrane accretion. Their apparent zonal structure is not a pre-collisional feature, but only the result of accretion and collision. 相似文献
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Non-avian theropod dinosaurs attained large body sizes, monopolising terrestrial apex predator niches in the Jurassic–Cretaceous.
From the Middle Jurassic onwards, Allosauroidea and Megalosauroidea comprised almost all large-bodied predators for 85 million
years. Despite their enormous success, however, they are usually considered absent from terminal Cretaceous ecosystems, replaced
by tyrannosaurids and abelisaurids. We demonstrate that the problematic allosauroids Aerosteon, Australovenator, Fukuiraptor and Neovenator form a previously unrecognised but ecologically diverse and globally distributed clade (Neovenatoridae, new clade) with the
hitherto enigmatic theropods Chilantaisaurus, Megaraptor and the Maastrichtian Orkoraptor. This refutes the notion that allosauroid extinction pre-dated the end of the Mesozoic. Neovenatoridae includes a derived
group (Megaraptora, new clade) that developed long, raptorial forelimbs, cursorial hind limbs, appendicular pneumaticity and
small size, features acquired convergently in bird-line theropods. Neovenatorids thus occupied a 14-fold adult size range
from 175 kg (Fukuiraptor) to approximately 2,500 kg (Chilantaisaurus). Recognition of this major allosauroid radiation has implications for Gondwanan paleobiogeography: The distribution of early
Cretaceous allosauroids does not strongly support the vicariant hypothesis of southern dinosaur evolution or any particular
continental breakup sequence or dispersal scenario. Instead, clades were nearly cosmopolitan in their early history, and later
distributions are explained by sampling failure or local extinction. 相似文献
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Ronan Allain Tiengkham Xaisanavong Philippe Richir Bounsou Khentavong 《Die Naturwissenschaften》2012,99(5):369-377
Spinosaurids are among the largest and most specialized carnivorous dinosaurs. The morphology of their crocodile-like skull, stomach contents, and oxygen isotopic composition of the bones suggest they had a predominantly piscivorous diet. Even if close relationships between spinosaurids and Middle Jurassic megalosaurs seem well established, very little is known about the transition from a generalized large basal tetanuran to the specialized morphology of spinosaurids. Spinosaurid remains were previously known from the Early to Late Cretaceous of North Africa, Europe, and South America. Here, we report the discovery of a new spinosaurid theropod from the late Early Cretaceous Savannakhet Basin in Laos, which is distinguished by an autapomorphic sinusoidal dorsosacral sail. This new taxon, Ichthyovenator laosensis gen. et sp. nov., includes well-preserved and partially articulated postcranial remains. Although possible spinosaurid teeth have been reported from various Early Cretaceous localities in Asia, the new taxon I. laosensis is the first definite record of Spinosauridae from Asia. Cladistic analysis identifies Ichthyovenator as a member of the sub-clade Baryonychinae and suggests a widespread distribution of this clade at the end of the Early Cretaceous. Chilantaisaurus tashouikensis from the Cretaceous of Inner Mongolia, and an ungual phalanx from the Upper Jurassic of Colorado are also referred to spinosaurids, extending both the stratigraphical and geographical range of this clade. 相似文献
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Gabbroic bodies in the Bralorne-Gold Bridge area of southwestern British Columbia are associated with the oceanic Bridge River complex of the western Canadian Cordillera, one of the suspect terranes accreted to North America in the Jurassic. The gabbros are locally cut by tonalites and are structurally interleaved with ultramafic rocks, phyllites, graphitic cherts, and carbonate lenses that comprise the lower part of the Bridge River complex. Their late Carboniferous crystallization age overlaps the depositional age of affiliated supracrustal rocks (Mississippian-Jurassic), some of which have been metamorphosed to blueschist facies. Compositionally, the gabbros resemble mafic plutonic rocks of ophiolitic complexes and gabbroic rocks of the nearby Shulaps Range. They display some affinity to oceanic island arc tholeiitic suites. The Bralorne and Shulaps gabbros include cumulates and appear to have been derived from a single, light REE-depleted, peridotitic source by melting and subsequent fractional crystallization/accumulation of various combinations of plagioclase, pyroxenes, and olivine. The tonalites are compositionally distinct from typical ophiolitic plagiogranites, but might be related to the associated gabbros. The gabbroic bodies occur within tectonic slivers derived from the oceanic crust that floored a deep ocean basin that existed during the late Paleozoic and early Mesozoic. The Bridge River complex comprises fragments of oceanic crust that were tectonically incorporated into an east-verging accretionary prism during a middle/late Triassic to Jurassic collisional event. 相似文献