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.


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 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bajpai, S., Thewissen, J. G. M., and Sahni, A. (1996). Indocetus (Cetacea, Mammalia) endocasts from Kachchh (India). J. Vertebr. Paleo. 16: 582–584.Google Scholar
  2. Barnes, L. G. (1985). Review: General features of the paleobiological evolution of Cetacea. Marine Mammal. Sci. 1: 90–93.Google Scholar
  3. Bateson, G. (1966). Problems in cetacean and other mammalian communication. In: Whales, Dolphins, and Porpoises, K. S. Norris, ed., pp. 569–579, University of California Press, Berkeley, CA.Google Scholar
  4. Breathnach, A. S. (1955). Observations on endocranial casts of recent and fossil cetaceans. J. Anat. 89: 533–546.Google Scholar
  5. Buchholtz, E. A. (1998). Implications of vertebral morphology for locomotor evolution in early Cetacea. In: The Emergence of Whales, J. G. M. Thewissen, ed., pp. 325–351. Plenum Press, New York.Google Scholar
  6. Connor, R. C., Mann, J., Tyack, P., and Whitehead, H. (1998). Social evolution in toothed whales. Trends Ecol. Evol. 13: 228–232.Google Scholar
  7. Conroy, G. C., and Vannier, M. W. (1984). Noninvasive three-dimensional computer imaging of matrix-filled fossil skulls by high-resolution computed tomography. Science 226: 456–458.Google Scholar
  8. Conroy, G. C., and Vannier, M. W. (1985). Endocranial volume determination of matrix-filled fossil skulls using high-resolution computed tomography. In: Hominid Evolution: Past, Present and Future, P. V. Tobias, ed., pp. 419–426, Alan R. Liss, New York.Google Scholar
  9. Conroy, G. C., and Vannier, M. W. (1986). Three-dimensional computer imaging: some anthropological applications. In: Primate Evolution: Vol. 1, J. G. Else and P. C. Lee, eds., pp. 211–222, Cambridge University Press, Cambridge.Google Scholar
  10. Conroy, G. C., Vannier, M. W., and Tobias, P. V. (1990). Endocranial features of Australopithecus africanus revealed by 2-and 3-D computed tomography. Science 217: 838–840.Google Scholar
  11. Dart, R. (1923). The brain of the Zeuglodontidae (Cetacea). Proc. Zool. Soc. Lond. 1923: 615–654.Google Scholar
  12. Eisenberg, J. F. (1986). Dolphin behavior and cognition: Evolutionary and ecological aspects. In: Dolphin Cognition and Behavior: A Comparative Approach, R. J. Schusterman, J. A. Thomas, and F. G. Wood, eds., pp. 261–270, Lawrence Erlbaum Associates, Hillsdale, New Jersey.Google Scholar
  13. Gaskin, D. E. (1982). Evolution of Cetacea. In: The Ecology of Whales and Dolophins, D. E. Gaskin, ed., pp. 159–199. Heinemann, New York.Google Scholar
  14. Gingerich, P. D. 1998. Paleobiological perspectives on Mesonychia, Archaeoceti, and the origin of whales. In: The Emergence of Whales, J. G. M. Thewissen, ed., pp. 423–449. Plenum Press, New York.Google Scholar
  15. Gingerich, P. D., Domning, D. P., Blane, C. E., and Uhen, M. D. (1994), Cranial morphology of Protosiren fraasi (Mammalia, Sirenia) from the middle Eocene of Egypt: a new study using computed tomography. Contrib. Museum. Paleontol., Univ. Michigan 29: 41–67.Google Scholar
  16. Glezer, I., Jacobs, M., and Morgane, P. (1988). Implications of the “initial brain” concept for brain evolution in Cetacea. Behav. Brain Sci. 11: 75–116.Google Scholar
  17. Herman, L. M. (1986). Cognition and language competencies of bottlenosed dolphins. In: Dolphin Cognition and Behavior: A Comparative Approach, R. J. Schusterman, J. A. Thomas, and F. G. Wood, eds., pp. 221–252, Lawrence Erlbaum Associates, Hillsdale, New Jersey.Google Scholar
  18. Jerison, H. J. (1963). Interpreting the evolution of the brain. Human Biol. 35: 263–291.Google Scholar
  19. Jerison, H. J. (1973). Evolution of the Brain and Intelligence. Academic Press, New York.Google Scholar
  20. Jerison, H. J. (1978). Brain and intelligence in whales. In: Whales and Whaling: Vol. 2, S. Frost, ed., pp. 159–197, C. J. Thompson, Canberra, Australia.Google Scholar
  21. Jerison, H. J. (1986). The perceptual world of dolphi. In: Dolphin Cognition and Behavior: A Comparative Approach, R. J. Schusterman, J. A. Thomas, and F. G. Wood, eds., pp. 141–166, Lawrence Erlbaum Associates, Hillsdale, New Jersey.Google Scholar
  22. Kellogg, R. (1936). A review of the Archaeoceti. Publ. Carnegie Inst. Wash. 482: 1–366.Google Scholar
  23. Luo, Z. (1998). Homology and transformation of cetacean ectotympanic structures. In: The Emergence of Whales, J. G. M. Thewissen, ed., pp. 269–301. Plenum Press, New York.Google Scholar
  24. Luo, Z., and Gingerich, P. D. (1999). Terrestrial Mesonychia to aquatic Cetacea: Transformation of the basicranium and evolution of hearing in whales. Univ. Mich. Papers Paleontol. 31: 1–98.Google Scholar
  25. Marino, L. (1995). Brain–Behavior Relationships in Cetaceans and Primates: Implications for the Evolution of Complex Intelligence. Unpublished doctoral dissertation, State University of New York, Albany.Google Scholar
  26. Marino, L. (1996). What can dolphins tell us about primate evolution? Evol. Anthropol. 5: 81–85.Google Scholar
  27. Marino, L. (1998). A comparison of encephalization levels between odontocete cetaceans and anthropoid primates. Brain Behav. Evol. 51: 230–238.Google Scholar
  28. Marples, B. J. (1949). Two endocranial casts of cetaceans from the Oligocene of New Zealand. Amer. J. Sci. 247: 462–471.Google Scholar
  29. Oelschlager, H. A. (1990). Evolutionary morphology and acoustics in the dolphin skull. In: Sensory Abilities of Cetaceans, J. Thomas and R. Kastelein, eds., pp. 137–162, Plenum Press, New York.Google Scholar
  30. Nishiwaki, M., and Kamiya, T. (1958). A beaked whale Mesoplodon stranded at Oiso Beacj Japan. Sci. Rept. Whales Res. Inst. 13: 58–83.Google Scholar
  31. Omura, H. (1958). North Pacific right whale. Sci. Rept. Whales Res. Inst. 13: 1–52.Google Scholar
  32. Omura, H. (1975). Osteological study of the minke whale from the Antarctic. Sci. Rept. Whales Res. Inst. 27: 1–36.Google Scholar
  33. Omura, H., Kasuya, T., Kato, H., and Wada, S. (1981). Osteological study of the Bryde's whales from the central south Pacific and eastern Indian Ocean. Sci. Rept. Whales Res. Inst. 33: 1–26.Google Scholar
  34. Radinsky, L. B. (1976). The brain of Mesonyx, a middle Eocene mesonychid condylarth. Fieldiana Field Museum Nat. Hist. Geol. Ser. 33: 323–337.Google Scholar
  35. Ridgway, S. H., and Wood, F. G. (1988). Dolphin brain evolution. Behav. Brain Sci. 11: 99–100.Google Scholar
  36. Ridgway, S. H., and Tarpley, R. J. (1996). Brain mass comparisons in Cetacea. In: Proceedings of the International Association for Aquatic Animal Medicine, Vol. 2, D. Abt, ed., pp. 55–57, University of Pennsylvania, Philadelphia, PA.Google Scholar
  37. Ridgway, S. H., Flanigan, N., and McCormick, J. (1966). Brain-spinal cord ratios in porpoises: Possible correlations with intelligence and ecology. Psychon. Sci. 6: 491–492.Google Scholar
  38. Silva, M., and Downing, J. A. (1995). CRC Handbook of Mammalian Body Masses. CRC Press, Boca Raton, FL.Google Scholar
  39. Uhen, M. (1996). Dorudon atrox (Mammalian, Cetacea): Form, Function, and Phylogenetic Relationships of an Archaeocete from the Late Middle Eocene of Egypt. Unpublished doctoral dissertation, University of Michigan, Ann Arbor, MI.Google Scholar
  40. Uhen, M. D. (2000). Replacement of deciduous first premolars and dental eruption in archaeocete whales. J. Mammal. 81: 123–133.Google Scholar
  41. Worthy, G. A., and Hickie, J. P. (1986). Relative brain size in marine mammals. Amer. Nat. 128: 445–459.Google Scholar

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

Personalised recommendations