Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls

Abstract

Modern members of the mammalian order Cetacea (whales, dolphins and porpoises) are obligate aquatic swimmers that are highly distinctive in morphology, lacking hair and hind limbs, and having flippers, flukes, and a streamlined body. Eocene fossils document much of cetaceans' land-to-water transition, but, until now, the most primitive representative for which a skeleton was known was clearly amphibious and lived in coastal environments. Here we report on the skeletons of two early Eocene pakicetid cetaceans, the fox-sized Ichthyolestes pinfoldi, and the wolf-sized Pakicetus attocki. Their skeletons also elucidate the relationships of cetaceans to other mammals. Morphological cladistic analyses have shown cetaceans to be most closely related to one or more mesonychians, a group of extinct, archaic ungulates, but molecular analyses have indicated that they are the sister group to hippopotamids. Our cladistic analysis indicates that cetaceans are more closely related to artiodactyls than to any mesonychian. Cetaceans are not the sister group to (any) mesonychians, nor to hippopotamids. Our analysis stops short of identifying any particular artiodactyl family as the cetacean sister group and supports monophyly of artiodactyls.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Postcranial osteology of pakicetids.
Figure 2: Skeletons of the pakicetid cetaceans Pakicetus (a) and Ichthyolestes (b).
Figure 3: Skulls of the pakicetids Pakicetus (H-GSP 96231) in dorsal (a) and lateral (b) view and Ichthyolestes (H-GSP 98134) in ventral view (c).
Figure 4: Phylogenetic relations of cetaceans to artiodactyls, mesonychians and primitive ungulates.

References

  1. Hulbert, R. C. Jr, Petkewich, R. M., Bishop, G. A., Bukry, D. & Aleshire, D. P. A new middle Eocene protocetid whale (Mammalia: Cetacea: Archaeoceti) and associated biota from Georgia. J. Paleontol. 72, 907–927 (1998).

    Article  Google Scholar 

  2. Thewissen, J. G. M. & Hussain, S. T. Systematic review of the Pakicetidae, early and middle Eocene Cetacea (Mammalia) from Pakistan and India. Bull. Carnegie Mus. Nat. Hist. 34, 220–238 (1998).

    Google Scholar 

  3. Luo, Z. & Gingerich, P. D. Terrestrial Mesonychia to aquatic Cetacea: transformation of the basicranium and evolution of hearing in whales. Univ. Michigan Pap. Paleontol. 31, 1–98 (1999).

    Google Scholar 

  4. O'Leary, M. A. & Geisler, J. H. The position of Cetacea within Mammalia: phylogenetic analysis of morphological data from extinct and extant taxa. Syst. Biol. 48, 455–490 (1999).

    Article  CAS  Google Scholar 

  5. Uhen, M. D. New species of protocetid archaeocete whale, Eocetus wardii (Mammalia, Cetacea) from the middle Eocene of North Carolina. J. Paleont. 73, 512–528 (1999).

    Article  Google Scholar 

  6. Luo, Z. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 269–301 (Plenum, New York, 1998).

    Book  Google Scholar 

  7. Thewissen, J. G. M., Hussain, S. T. & Arif, M. Fossil evidence for the origin of aquatic locomotion in archaeocete whales. Science 263, 210–212 (1994).

    Article  ADS  CAS  Google Scholar 

  8. Thewissen, J. G. M., Madar, S. I. & Hussain, S. T. Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan. Courier Forschungsinstitut Senckenberg 191, 1–86 (1996).

    Google Scholar 

  9. Thewissen, J. G. M. & Fish, F. E. Locomotor evolution in the earliest cetaceans: functional model, modern analogues, and paleontological evidence. Paleobiology 23, 482–490 (1997).

    Article  Google Scholar 

  10. Milinkovitch, M. C. & Thewissen, J. G. M. Even-toed fingerprints on whale ancestry. Nature 388, 622–624 (1997).

    Article  ADS  CAS  Google Scholar 

  11. Luo, Z. In search of whales' sisters. Nature 404, 235–237 (2000).

    Article  CAS  Google Scholar 

  12. Gingerich, P. D., Russell, D. E. & Shah, S. M. I. Origin of whales in epicontinental remnant seas: new evidence from the early Eocene of Pakistan. Science 220, 403–406 (1983).

    Article  ADS  CAS  Google Scholar 

  13. Kellogg, R. A Review of the Archaeoceti (Carnegie Inst. Washington, Washington, 1936).

    Google Scholar 

  14. Gingerich, P. D., Smith, B. H. & Simons, E. L. Hind limbs of Eocene Basilosaurus: evidence of feet in whales. Science 249, 154–157 (1990).

    Article  ADS  CAS  Google Scholar 

  15. Uhen, M. D. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 29–61 (Plenum, New York, 1998).

    Book  Google Scholar 

  16. Bajpai, S. & Thewissen, J. G. M. A new diminutive Eocene whale from Kachchh (Gujarat, India) and its implications for locomotor evolution of cetaceans. Curr. Sci. 79, 1478–1482 (2000).

    Google Scholar 

  17. Zhou, X., Sanders, W. J. & Gingerich, P. D. Functional and behavioral implications of vertebral structure in Pachyaena ossifraga (Mammalia, Mesonychia). Contrib. Mus. Paleontol. Univ. Michigan 28, 289–319 (1992).

    Google Scholar 

  18. Thewissen, J. G. M. & Hussain, S. T. Postcranial osteology of the most primitive artiodactyl Diacodexis pakistanensis (Dichobunidae). Anat. Histol. Embryol. 19, 37–48 (1990).

    Article  CAS  Google Scholar 

  19. Madar, S. I., Thewissen, J. G. M. & Hussain, S. T. Additional holotype remains of Ambulocetus natans (Cetacea, Ambulocetidae), and their implications for locomotion in early whales. J. Vertebr. Paleont. (in the press).

  20. Howell, A. B. Aquatic Mammals: Their Adaptations to Life in the Water (Charles Thomas, Baltimore, 1930).

    Google Scholar 

  21. Howell, A. B. Speed in Animals: Their Specializations for Running and Leaping (Univ. Chicago Press, Chicago, 1944).

    Google Scholar 

  22. King, J. E. Seals of the World (Cornell Univ. Press, Ithaca, 1991).

    Google Scholar 

  23. Shaeffer, B. Notes on the origin and function of the artiodactyl tarsus. Am. Mus. Novit. 1356, 1–26 (1947).

    Google Scholar 

  24. Thewissen, J. G. M. & Madar, S. I. Ankle morphology of the earliest cetaceans and its implications for the phylogenetic relations among ungulates. Syst. Biol. 48, 21–30 (1999).

    Article  CAS  Google Scholar 

  25. Vaughan, T. A. Mammalogy (Saunders College, New York, 1986).

    Google Scholar 

  26. Bajpai, S. & Thewissen, J. G. M. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 213–233 (Plenum, New York, 1998).

    Book  Google Scholar 

  27. Weber, M. Die Säugetiere (Gustav Fischer, Jena, 1928).

    Google Scholar 

  28. Gingerich, P. D., Raza, M. S., Arif, M., Anwar, M. & Zhou, X. New whale from the Eocene of Pakistan and the origin of cetacean swimming. Nature 368, 844–847 (1994).

    Article  ADS  Google Scholar 

  29. O'Leary, M. A. & Uhen, M. D. The time of origin of whales and the role of behavioral changes in the terrestrial-aquatic transition. Paleobiology 25, 534–556 (1999).

    Article  Google Scholar 

  30. Thewissen, J. G. M., Williams, E. M. & Hussain, S. M. Eocene mammal faunas from northern Indo-Pakistan. J. Vertebr. Paleont. 21, 347–366 (2001).

    Article  Google Scholar 

  31. Thewissen, J. G. M. & Hussain, S. T. Origin of underwater hearing in whales. Nature 361, 444–445 (1993).

    Article  ADS  CAS  Google Scholar 

  32. Hemilä, S., Nummela, S. & Reuter, T. A model of the odontocete middle ear. Hearing Res. 133, 82–97 (1999).

    Article  Google Scholar 

  33. Rado, R., Himelfarb, M., Arensberg, B., Terkel, J. & Wollberg, Z. Are seismic communication signals transmitted by bone conduction in the blind mole rat? Hearing Res. 41, 23–30 (1989).

    Article  CAS  Google Scholar 

  34. Lenhardt, M. L. Bone conduction hearing in turtles. J. Audit. Res. 22, 153–160 (1982).

    CAS  Google Scholar 

  35. Geisler, J. H. & Luo, Z. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 163–212 (Plenum, New York, 1998).

    Book  Google Scholar 

  36. O'Leary, M. A. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 133–161 (Plenum, New York, 1998).

    Book  Google Scholar 

  37. Luckett, W. P. & Hong, N. Phylogenetic relationships between the orders Artiodactyla and Cetacea: a combined assessment of morphological and molecular evidence. J. Mamm. Evol. 5, 127–182 (1998).

    Article  Google Scholar 

  38. Shimamura, M. et al. Molecular evidence from retroposons that whales form a clade within even-toed ungulates. Nature 388, 666–670 (1997).

    Article  ADS  CAS  Google Scholar 

  39. Gatesy, J. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 63–111 (Plenum, New York, 1998).

    Book  Google Scholar 

  40. Milinkovitch, M. C., Bérubé, M. & Palsbøll, P. J. in The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea (ed. Thewissen, J. G. M.) 113–131 (Plenum, New York, 1998).

    Book  Google Scholar 

  41. Nikaido, M., Rooney, A. P. & Okada, N. Phylogenetic relationships among cetartiodactyls based on insertions of short and long interspersed elements: hippopotamuses are the closest extant relatives of whales. Proc. Natl Acad. Sci. USA 96, 10261–10266 (1999).

    Article  ADS  CAS  Google Scholar 

  42. Gentry, A. W. & Hooker, J. J. in The Phylogeny and Classification of the Tetrapods, Vol. 2: Mammals (ed. Benton, M. J.) 235–272 (Clarendon, Oxford, 1988).

    Google Scholar 

  43. Bajpai, S. & Gingerich, P. D. A new Eocene archaeocete (Mammalia, Cetacea) from India and the time of origin of whales. Proc. Natl Acad. Sci. USA 95, 15464–15468 (1998).

    Article  ADS  CAS  Google Scholar 

  44. Thewissen, J. G. M. Phylogenetic aspects of cetacean origins: a morphological perspective. J. Mammal. Evol. 2, 157–184 (1994).

    Article  Google Scholar 

  45. Thewissen, J. G. M., Madar, S. I. & Hussain, S. T. Whale ankles and evolutionary relationships. Nature 395, 452 (1998).

    Article  ADS  CAS  Google Scholar 

  46. Naylor, G. J. P. & Adams, D. C. Are the fossil data really at odds with the molecular data? Morphological evidence for Cetartiodactyla phylogeny reexamined. Syst. Biol. 50, 444–453 (2001).

    CAS  Google Scholar 

  47. Swofford, D. L. PAUP 4.0b8 Phylogenetic Analysis Using Parsimony (and Other Methods) (Sinauer, Sunderland, Massachusetts, 1998).

    Google Scholar 

  48. Gingerich, P. D., Haq, M.-u., Zalmout, I., Khan, I. H. & Malkani, M. S. Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan. Science (in the press).

Download references

Acknowledgements

We thank M. Arif, S. Bajpai, J. Erfurt, A. Friscia, M. Hellmund, S. Madar, M. Raza, J. Quade and the Geological Survey of Pakistan for assistance in field work, access to collections and laboratories, and/or discussions. M. Tomasko prepared Fig. 1. Funding for this research was provided by the National Science Foundation (EAR 9902830).

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to J. G. M. Thewissen.

Supplementary information

Rights and permissions

Reprints and permissions

About this article

Cite this article

Thewissen, J., Williams, E., Roe, L. et al. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature 413, 277–281 (2001). https://doi.org/10.1038/35095005

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/35095005

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing