Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation

  title={Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation},
  author={Robert Evan Sloan and J. Keith Rigby and Leigh M. Van Valen and Diane L. Gabriel},
  pages={629 - 633}
Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last dinosaurs known are from a channel that contains teeth of Mantuan mammals, seven species of… Expand
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