نتایج جستجو برای: cretaceous

تعداد نتایج: 9055  

Journal: :Science 1999
Sereno Beck Dutheil Larsson Lyon Moussa Sadleir Sidor Varricchio Wilson

Lower Cretaceous fossils from central Niger document the succession of sauropod dinosaurs on Africa as it drifted into geographic isolation. A new broad-toothed genus of Neocomian age ( approximately 135 million years ago) shows few of the specializations of other Cretaceous sauropods. A new small-bodied sauropod of Aptian-Albian age ( approximately 110 million years ago), in contrast, reveals ...

Journal: :Science 1998
Sampson Witmer Forster Krause O'Connor Dodson Ravoavy

Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis o...

Journal: :journal of tethys 0

in order to microfacies studies of the cretaceous deposits, a section called korkouh was selected in kerman province in central iran area. the korkouh is on the bidou formation with angular unconformity and underlain by paleogene conglomerates with an erosional surface. the studied section basically contains lime and dolomitic limestone with the thickness of 146 meters with new fossils such as ...

Journal: :Science 2007
G V R Prasad O Verma A Sahni V Parmar A Khosla

The sedimentary record documenting the northward drift of India (Late Cretaceous to late Early Eocene) has recently provided important clues to the evolution, radiation, and dispersal of mammals. Here, we report a definitive Late Cretaceous (Maastrichtian) archaic ungulate (Kharmerungulatum vanvaleni genus et species nova) from the Deccan volcano-sedimentary sequences exposed near Kisalpuri vil...

Journal: :Science 2004
Adina Paytan Miriam Kastner Douglas Campbell Mark H Thiemens

The exogenic sulfur cycle is tightly coupled with the carbon and oxygen cycles, and therefore a central component of Earth's biogeochemistry. Here we present a high-resolution record of the sulfur isotopic composition of seawater sulfate for the Cretaceous. The general enrichment of isotopically light sulfur that prevailed during the Cretaceous may have been due to increased volcanic and hydrot...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2003
Rowan Lockwood

Ecological studies suggest that rare taxa are more likely to go extinct than abundant ones, but the influence of abundance on survivorship in the fossil record has received little attention. An analysis of Late Maastrichtian bivalve subgenera from the North American Coastal Plain found no evidence that survivorship is tied to abundance across the end-Cretaceous mass extinction (65 million years...

2017
Carlos Roberto A. Candeiro Stephen L. Brusatte André Luis de Souza

We review the fossil records of spinosaurid dinosaurs in order to discuss this group’s evolution and distribution in Europe and North Africa during the Early Cretaceous. Along with their eastern Laurasian distribution during the Cretaceous, these theropods have been found in coastal deposits of Europe and North Africa dated from the Barremian to the Cenomanian. The main occurrences of spinosaur...

Journal: :Science 2006
Hai-Lu You Matthew C Lamanna Jerald D Harris Luis M Chiappe Jingmai O'connor Shu-An Ji Jun-Chang Lü Chong-Xi Yuan Da-Qing Li Xing Zhang Kenneth J Lacovara Peter Dodson Qiang Ji

Three-dimensional specimens of the volant fossil bird Gansus yumenensis from the Early Cretaceous Xiagou Formation of northwestern China demonstrate that this taxon possesses advanced anatomical features previously known only in Late Cretaceous and Cenozoic ornithuran birds. Phylogenetic analysis recovers Gansus within the Ornithurae, making it the oldest known member of the clade. The Xiagou F...

Journal: :Science 1989
E J Barron W H Peterson

Three-dimensional numerical ocean circulation model experiments that were designed to evaluate the circulation characteristics for the mid-Cretaceous ( approximately 100 million years ago) show that the primary direction of flow through the Tethys Ocean was eastward; in contrast, a westward flowing circumglobal Tethys current has been a consistent feature of earlier reconstructions of Cretaceou...

Journal: :پژوهش نفت 0

lurestan province is petroliferous area. the reserved oil are in ilam and sarvak  (cretaceous ) and kangan ( lower triassic ) and dalan (permian) formations. the lurestan area had high exploration activity but contribution of source rocks in hydrocarbon accumulations isn’t clear. in this paper essential elements and process of hydrocarbon accumulation are introduced. candidate  source  rocks ar...

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