Journal of Mammalian Evolution

, Volume 7, Issue 2, pp 81–94 | Cite as

Endocranial Volume of Mid-Late Eocene Archaeocetes (Order: Cetacea) Revealed by Computed Tomography: Implications for Cetacean Brain Evolution

  • Lori Marino
  • Mark D. Uhen
  • Bruno Frohlich
  • John Matthew Aldag
  • Caroline Blane
  • David Bohaska
  • Frank C. WhitmoreJr.
Article

Abstract

The large brain of modern cetaceans has engendered much hypothesizing about both the intelligence of cetaceans (dolphins, whales, and porpoises) and the factors related to the evolution of such large brains. Despite much interest in cetacean brain evolution, until recently there have been few estimates of brain mass and/or brain–body weight ratios in fossil cetaceans. In the present study, computed tomography (CT) was used to visualize and estimate endocranial volume, as well as to calculate level of encephalization, for two fully aquatic mid-late Eocene archaeocete species, Dorudon atrox and Zygorhiza kochii. The specific objective was to address more accurately and more conclusively the question of whether relative brain size in fully aquatic archaeocetes was greater than that of their hypothesized sister taxon Mesonychia. The findings suggest that there was no increase in encephalization between Mesonychia and these archaeocete species.

archaeocete endocranial volume encephalization computed tomography Cetacea 

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Copyright information

© Plenum Publishing Corporation 2000

Authors and Affiliations

  • Lori Marino
    • 1
  • Mark D. Uhen
    • 2
  • Bruno Frohlich
    • 3
  • John Matthew Aldag
    • 4
  • Caroline Blane
    • 5
  • David Bohaska
    • 6
  • Frank C. WhitmoreJr.
    • 7
  1. 1.Neuroscience and Behavioral Biology Program, Psychology BuildingEmory UniversityAtlanta
  2. 2.Department of Paleontology and ZoologyCranbrook Institute of ScienceBloomfield Hills
  3. 3.Department of AnthropologySmithsonian InstitutionWashington
  4. 4.Neuroscience and Behavioral Biology Program, Psychology BuildingEmory UniversityAtlanta
  5. 5.Department of RadiologyUniversity of MichiganAnn Arbor
  6. 6.Department of PaleobiologySmithsonian InstitutionWashington
  7. 7.U.S. Geological Survey and Department of PaleobiologySmithsonian InstitutionWashington

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