scholarly journals A transitional snake from the Late Cretaceous period of North America

Nature ◽  
2012 ◽  
Vol 488 (7410) ◽  
pp. 205-208 ◽  
Author(s):  
Nicholas R. Longrich ◽  
Bhart-Anjan S. Bhullar ◽  
Jacques A. Gauthier
2010 ◽  
Vol 148 (2) ◽  
pp. 334-339 ◽  
Author(s):  
ERIC BUFFETAUT ◽  
ATTILA ŐSI ◽  
EDINA PRONDVAI

AbstractThe fragmentary pterosaur material from the Campanian Grünbach Formation (Gosau Group) of Muthmannsdorf (Austria), previously identified as Ornithocheirus buenzeli Bunzel, 1871, is revised. A lower jaw fragment shows a helical type of articulation, which is known in several families of pterosaurs, and cannot be identified with great accuracy. The proximal part of a humerus shows distinctive features that allow it to be referred to as a member of the family Azhdarchidae, which is widespread in the Late Cretaceous Period of Europe. Ornithocheirus buenzeli is considered a nomen dubium. The pterosaur material from the Grünbach Formation cannot be used as evidence for the presence of ornithocheirids in the Late Cretaceous of Europe.


1993 ◽  
Vol 40 ◽  
pp. 9-32
Author(s):  
E. Håkansson ◽  
C. Heinberg ◽  
C. Hjort ◽  
P. Mølgaard ◽  
S. A. S. Pedersen

The 1985 expedition constitutes the first comprehensive investigation of the isolated, hyperarctic semi­nunatak Kilen in eastern North Greenland. Well over 3 km of generally marine, elastic sediments are preserved from the Late Jurassic to Late Cretaceous period. While half this amount accumulated in ·a comparatively stable tectonic regime prevailing during Late Jurassic and Early Cretaceous time, the Late Cretaceous (Turonian-Coniacian) sediments are characterized by their deposition in a local pull-apart basin developed in the regional Wandel Hav Strike-Slip Mobile Belt. Subsequent, localized compression along this belt has deformed the entire sequence rather severely in a complex series of en echelon domal folding and thrusting, most likely during the later part of the Cretaceous. Quaternary marine sediments of probable interglacial origin (> 100.000 years old) have been found to contain a mollusc fauna requiring temperatures above the present level. Flade lsblink, the largest local icecap in Greenland, is composed of several semi-independant ice domes, and there is evidence that the history of this icecap deviates significantly from that of the Inland Ice. A total of 34 species of higher plants, 29 species of birds, and 11 species of mammals have been recorded from Kilen; vegetation studies indicate a July mean temperature of around 2.5°C.


2020 ◽  
Author(s):  
Cunjian Zhang ◽  
Jingdong Liu ◽  
Youlu Jiang

<p>Research on overpressure evolution and its formation mechanisms is of great significance for revealing reservoir formation mechanisms and predicting formation pressures in oil and gas reservoirs before drilling. However, research methods addressing overpressure evolution are not without issues. The fluid inclusion PVT simulation and basin simulation can be used to investigate the paleo-pressure.</p> <p>The homogenization temperatures of inclusions were tested. The accuracy of the microscopic laser Raman spectroscopy analysis is too limited to fully test the components of gaseous hydrocarbon inclusions so that the organic components of the natural gas in the present-day gas reservoirs represented the gaseous hydrocarbon inclusions. In addition, the vapor-liquid ratio of gaseous hydrocarbon inclusions cannot be measured by CLSM. Firstly, A series of images at different slice depths was obtained by adjusting the focal length of a high-resolution microscope. Secondly, CorelDRAW software was used to calculate the areas of inclusions and bubbles; fitting functions were established between the inclusion areas and slice depths, and between the bubble areas and slice depths. Finally, the inclusion and bubble volumes were integrated to obtain the vapor-liquid ratios of the inclusions. PVTsim software can calculate the trapping pressures of inclusions. Combined with basin simulation, the evolution of paleo-pressure can be determined.</p> <p>The above methods were used to investigate the paleo-pressure of the Upper Triassic Xujiahe Formation in the northeast portion of the Sichuan Basin. Overpressure began to develop in the Middle Jurassic period. Due to hydrocarbon generation taking place, the formation pressure increased rapidly from the Middle Jurassic period to the early Late Cretaceous period. Since the early Late Cretaceous period, the formation pressure has gradually decreased due to tectonic uplift and erosion. From the Oligocene period to the present, the formation pressure have increased again in local areas due to tectonic compression.</p>


1994 ◽  
Vol 6 (3) ◽  
pp. 401-408 ◽  
Author(s):  
R. C. R. Willan ◽  
R. J. Pankhurst ◽  
F. Hervé

Fifteen samples of very low-grade mudstones from two widely separated sections in the Miers Bluff Formation on Hurd Peninsula yield an Rb-Sr errorchron (MSWD=8.9) corresponding to an age of 243 ± 8 Ma. This age is interpreted as representing effective homogenization, on a kilometres scale, during turbidite deposition and diagenesis in early Triassic times. The initial 87Sr/86Sr ratio 0.7085 ± 0.0003 represents a mature crustal source and is consistent with the re-working of material comparable to that eroded from the Chilean fore-arc accretionary complex. Four further samples, collected near to a zone of quartz-carbonate veins, lie to the right of the errorchron, with two samples having unusually low Sr contents. These samples fall on a 113 Ma reference line and indicate metasomatic disturbance in Cretaceous times. Metasomatism was probably related to hydrothermal alteration accompanying widespread silicification and quartz veining on western Hurd Peninsula. A mid-to late Cretaceous age for metasomatic disturbance agrees with field relations which indicate that the hydrothermal activity preceded or was coeval with the mid- to late Cretaceous period of volcanism on Livingston Island. Hence the hydrothermal rocks are not related to the Eocene Barnard Point pluton, as previously suggested.


Vista ◽  
2019 ◽  
pp. 217-228
Author(s):  
Victoria Ahrens

This is a visual essay that meanders. It is based around my encounter with palm trees and my grandfather’s silver print photographs, collated in an album that dates back to the 1930s. Henry Richard Ahrens was a keen photographer, though I had never seen any of his images until 2010 when I was given one of his albums by a relative who knew I was a photographer and writer. He died before I could get to know him. His photographs have a particular sensibility to them, with a multitude of self-portraits, and often, a hand written phrase to go with them. I am told he developed his films himself. He is often pictured next to palm trees in his photographs. These palms he photographed are particularly fascinating to me. They represent one of the few genus that extend back to the late Cretaceous period, a dinosaur of a plant species. With their many variations, they take on a poetic and utopian presence, their seeds having been disseminated through colonial exchanges, botanical curiosity and commercial interests. Found in so many surprising corners of the world, the palm expresses our need to explore, while becoming a symbol of resistance to discourses of nationalism and anti-immigration sentiment. This essay reflects a personal ethnography through the interconnected and material presence of the palm in London, Buenos Aires and in the photograph itself.


2018 ◽  
Author(s):  
Chase D Brownstein

During the Cretaceous period, North America was divided into two landmasses, the eastern Appalachia and western Laramidia. Recent research on several sites scattered across the eastern margin of North America has allowed for the analysis of vertebrate faunas from the once obscured terrestrial fossil record of Appalachia, revealing the landmass harbored a distinctive fauna composed of mostly relict forms. One geological unit that has produced a comparatively extensive record of terrestrial vertebrates, including non-avian dinosaurs, is the Tar Heel Formation of North Carolina. Here, I report the first definitive occurrence of a dromaeosaurid from the Tar Heel Formation in the form of a tooth from a fairly large member of that group. This tooth, like others previously discovered from the southeastern portion of North America, compares favorably with those of saurornitholestine dromaeosaurids from the western United States and Canada. The North Carolina tooth differs in morphology and size from previously reported southeastern North American dromaeosaurid teeth, but is still assignable to a saurornitholestine dromaeosaurid, evincing that the diversity of carnivorous bird-like dinosaurs in the southeastern part of North America during the Late Cretaceous may have been rather low. The tooth, which is intermediate in size between those of smaller dromaeosaurids like Saurornitholestes and gigantic forms like Dakotaraptor, helps fill the gap between larger- and smaller-bodied dromaeosaurids from the Late Cretaceous.


2021 ◽  
Author(s):  
Tibor Pecsics

ABSTRACT The first trace fossils in Hungary, dinosaur footprints, were found in the coal mines of the Mecsek Mountains. The footprints belonged to small theropod dinosaurs. The first fossil bones of vertebrate animals from present-day Hungary were found in 2000 in the mountainous region of Bakony. Numerous taxa have been collected from the locality of Iharkút. These fossils represent a diverse fauna (including fishes, amphibians, turtles, lizards, crocodilians, dinosaurs, birds, and pterosaurs) that lived between 85.8 and 83.5 m.y. ago in the Santonian Age during the Late Cretaceous period. Paleoart can depict these fossil remains in an engaging way to help inform the public about the ancient creatures of Hungary. This chapter provides an overview of how the Mesozoic vertebrates from Hungary have been reconstructed for scientists and the public.


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