نتایج جستجو برای: cretaceous

تعداد نتایج: 9055  

Journal: :iranian journal of earth science 0
fatemeh hadavi professor, department of geology, ferdowsi university of mashhad, mashhad, iran marziyeh notghi moghaddam assistant professor, department of geology, payame noor university, tehran, iran lida khodadadi department of geology, payame noor university, tehran, iran

calcareous nannofossil assemblages recovered from a long, continuous section have been described from the sarayan region in lut block in east iran. the marine upper cretaceous sediments of this section yield medium diverse and well-preserved calcareous nannofossil assemblages. a structural analysis of upper cretaceous calcareous nannofloras has revealed 30 nannofossil species. a revised zonatio...

Journal: :Nature communications 2012
Stephen L Brusatte Richard J Butler Albert Prieto-Márquez Mark A Norell

The extinction of non-avian dinosaurs 65 million years ago is a perpetual topic of fascination, and lasting debate has focused on whether dinosaur biodiversity was in decline before end-Cretaceous volcanism and bolide impact. Here we calculate the morphological disparity (anatomical variability) exhibited by seven major dinosaur subgroups during the latest Cretaceous, at both global and regiona...

2013
Bo Wang Haichun Zhang Edmund A. Jarzembowski

The Coleoptera (beetles) constitute almost one-fourth of all known life-forms on earth. They are also among the most important pollinators of flowering plants, especially basal angiosperms. Beetle fossils are abundant, almost spanning the entire Early Cretaceous, and thus provide important clues to explore the co-evolutionary processes between beetles and angiosperms. We review the fossil recor...

Journal: :Proceedings. Biological sciences 2008
Nathan D Smith Peter J Makovicky Federico L Agnolin Martín D Ezcurra Diego F Pais Steven W Salisbury

The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian therop...

Journal: :Science 2000
P Wilf C C Labandeira W J Kress C L Staines D M Windsor A L Allen K R Johnson

Stereotyped feeding damage attributable solely to rolled-leaf hispine beetles is documented on latest Cretaceous and early Eocene ginger leaves from North Dakota and Wyoming. Hispine beetles (6000 extant species) therefore evolved at least 20 million years earlier than suggested by insect body fossils, and their specialized associations with gingers and ginger relatives are ancient and phylogen...

1998
Barry Ryan Angelo Ledda

The Jura-Cretaceous coal seams of the Currier, Mist Mountain, &thing and Gates formations generally formed in delta or strand plain environments with little marine influence. The sulphur contents of coal from these formations is therefore generally low, nearly always less than I % and often less than 0.5 %. Coalbearing formations of the Cretaceous Nanaimo and Skeena groups were deposited in coa...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2002
Conrad C Labandeira Kirk R Johnson Peter Wilf

Evidence for a major extinction of insect herbivores is provided by presence-absence data for 51 plant-insect associations on 13,441 fossil plant specimens, spanning the Cretaceous/Paleogene boundary in southwestern North Dakota. The most specialized associations, which were diverse and abundant during the latest Cretaceous, almost disappeared at the boundary and failed to recover in younger st...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2004
Catarina Rydin Kaj Raunsgaard Pedersen Else Marie Friis

Gnetales comprise three unusual genera of seed plants, Ephedra, Gnetum, and Welwitschia. Their extraordinary morphological diversity suggests that they are survivors of an ancient, more diverse group. Gnetalean antiquity is also supported by fossil data. Dispersed "ephedroid" (polyplicate) pollen first appeared in the Permian >250 million years ago (Myr), and a few megafossils document the pres...

2009
KIYOSHI ASANO

IN THIS PAPER the discovery in Japan of smaller Foraminifera from the Upper Cretaceous strata is recorded for the firsi: time. This contribution, in addition to its specific biostratigraphic application in Japan, has further interest by reason of its extension of the geo. graphic range ,of the widely distributed Cretaceous pelagic foraminiferan, Globotruncana. In the north Pacific region, Globo...

2008
J. Zhou C. J. Poulsen D. Pollard T. S. White

[1] We have developed a coupled ocean-atmosphere general circulation model, the GENESIS-MOM model, with the ability to transport and fractionate water isotopes in the ocean and atmosphere. The model is used to predict modern and Cretaceous precipitation and seawater dO. The model reproduces the large-scale modernday isotopic distribution. In the zonal mean, the difference between simulated and ...

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