Brawn before brains in placental mammals after the end-Cretaceous extinction

  title={Brawn before brains in placental mammals after the end-Cretaceous extinction},
  author={Ornella C. Bertrand and Sarah L. Shelley and Thomas E. Williamson and John R. Wible and Stephen G. B. Chester and John J. Flynn and Luke T. Holbrook and Tyler R. Lyson and Jin Meng and Ian M. Miller and Hans P. P{\"u}schel and Thierry Smith and Michelle Spaulding and Zhijie Jack Tseng and Stephen Louis Brusatte},
  pages={80 - 85}
Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a… 
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