Skip to main content
Advanced Search

Filters: Tags: CRETACEOUS (X) > Extensions: Citation (X)

3 results (87ms)   

View Results as: JSON ATOM CSV
thumbnail
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...
thumbnail
The lower part of the Cretaceous Sego Sandstone Member of the Mancos Shale in east-central Utah contains three 10- to 20-m thick layers of tide-deposited sandstone arranged in a forward- and then backward-stepping stacking pattern. Each layer of tidal sandstone formed during an episode of shoreline regression and transgression, and offshore wave-influenced marine deposits separating these layers formed after subsequent shoreline transgression and marine ravinement. Detailed facies architecture studies of these deposits suggest sandstone layers formed on broad tide-influenced river deltas during a time of fluctuating relative sea-level. Shale-dominated offshore marine deposits gradually shoal and become more sandstone-rich...
Modern biological soil crusts develop under semiarid to arid conditions and are characterized by diverse communities of micro- and macro-organisms. The upper meter of the Upper Cretaceous capping sandstone member of the Wahweap Formation in Grand Staircase-Escalante National Monument, Utah contains an outcrop of an ancient biological soil crust preserved in matrix-rich quartz sandstone. The interpretation is based in comparison with modern biological soil crust analogs, specifically similarities in morphological expression, sorting, and proximity to associated eolianites. This study reports on this rarely recognized type of paleosol, a biological soil crust and discusses the sedimentologic and paleoclimatic implications....
    map background search result map search result map Sharp-based, tide-dominated deltas of the Sego Sandstone, Book Cliffs, Utah, USA First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition. Sharp-based, tide-dominated deltas of the Sego Sandstone, Book Cliffs, Utah, USA First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition.