نتایج جستجو برای: early cretaceous

تعداد نتایج: 692756  

2016
Xiaolin Zhang Kefan Chen Dongping Hu Jingeng Sha

The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic...

Journal: :Proceedings. Biological sciences 2001
N Wikström V Savolainen M W Chase

Growing evidence of morphological diversity in angiosperm flowers, seeds and pollen from the mid Cretaceous and the presence of derived lineages from increasingly older geological deposits both imply that the timing of early angiosperm cladogenesis is older than fossil-based estimates have indicated. An alternative to fossils for calibrating the phylogeny comes from divergence in DNA sequence d...

2017
Qingqing Zhang Bo Wang

The Diptera (true flies) is one of the most species-abundant orders of Insecta, and it is also among the most important flower-visiting insects. Dipteran fossils are abundant in the Mesozoic, especially in the Late Jurassic and Early Cretaceous. Here, we review the fossil record and early evolution of some Mesozoic lower brachyceran flies together with new records in Burmese amber, including Ta...

2006
E. W. Baker S. E. Palmer W. Y. Huang

Even thick sequences of sediments in marine depositional basins contain only limited segments of the record of chlorophyll diagenesis. Extracts from Pleistocene deep-sea sediments (Baker and Smith, 1973a) yielded extensive information concerning early chlorin transformations. Investigations of marine sediments of Pliocene and Miocene age resulted in the first reports of free base porphyrins occ...

Journal: :Science 2009
Dong Ren Conrad C Labandeira Jorge A Santiago-Blay Alexandr Rasnitsyn ChungKun Shih Alexei Bashkuev M Amelia V Logan Carol L Hotton David Dilcher

The head and mouthpart structures of 11 species of Eurasian scorpionflies represent three extinct and closely related families during a 62-million-year interval from the late Middle Jurassic to the late Early Cretaceous. These taxa had elongate, siphonate (tubular) proboscides and fed on ovular secretions of extinct gymnosperms. Five potential ovulate host-plant taxa co-occur with these insects...

2011

T paper examines how the understanding of the prospectivity of the Liberia-Sierra Leone Basin has developed over the last 40 years largely due to improvements in seismic data over this period. A series of basins developed between major transform fault zones associated with the opening of the South Atlantic Ocean from the early Cretaceous onward. The Liberia-Sierra Leone Basin forms part of the ...

2016
Thomas John Dixon Halliday Paul Upchurch Anjali Goswami

The effect of the Cretaceous-Palaeogene (K-Pg) mass extinction on the evolution of many groups, including placental mammals, has been hotly debated. The fossil record suggests a sudden adaptive radiation of placentals immediately after the event, but several recent quantitative analyses have reconstructed no significant increase in either clade origination rates or rates of character evolution ...

2014
Friðgeir Grímsson Reinhard Zetter Heidemarie Halbritter Guido W. Grimm

The fossil record of Aponogeton (Aponogetonaceae) is scarce and the few reported macrofossil findings are in need of taxonomic revision. Aponogeton pollen is highly diagnostic and when studied with light microscopy (LM) and scanning electron microscopy (SEM) it cannot be confused with any other pollen types. The fossil Aponogeton pollen described here represent the first reliable Cretaceous and...

2014
Xiaoting Zheng Jingmai K. O'Connor Fritz Huchzermeyer Xiaoli Wang Yan Wang Xiaomei Zhang Zhonghe Zhou

A crop adapted for an herbivorous diet of seeds has previously been documented in the Early Cretaceous birds Sapeornis and Hongshanornis. Here we report on several specimens of Yanornis that preserve a crop containing fish. One specimen preserves two whole fish in the oesophagus, indicating that Early Cretaceous birds shared trophic specializations with Neornithes for the increased energetic de...

2013
Peter A. Hochuli Susanne Feist-Burkhardt

Here we report on angiosperm-like pollen and Afropollis from the Anisian (Middle Triassic, 247.2-242.0 Ma) of a mid-latitudinal site in Northern Switzerland. Small monosulcate pollen grains with typical reticulate (semitectate) sculpture, columellate structure of the sexine and thin nexine show close similarities to early angiosperm pollen known from the Early Cretaceous. However, they differ i...

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