Reconstructing Body Size in Extinct Crown Cetacea (Neoceti) Using Allometry, Phylogenetic Methods and Tests from the Fossil Record

  • Nicholas D. PyensonEmail author
  • Simon N. Sponberg
Original Paper


Living cetaceans exhibit interspecific size ranging across several orders of magnitude, and rank among the largest vertebrates ever. Details of how cetaceans evolved different body sizes, however, remain obscure, because they lack basic morphological proxies that have been traditionally used in other fossil vertebrates. Here, we reconstruct the body size of extinct crown group cetaceans (Neoceti) using different regression methods on extant skull and length data, in a phylogenetic context. Because most fossil cetaceans are fragmentary, we developed regression equations to predict total length based on cranial metrics that are preserved on most fossil crania. The resultant regression equations are based on a database of skull and length data from most extant lineages of cetaceans (n = 45 species; 272 specimens), sampling all living mysticete genera and all major clades of odontocetes. In generating predictive equations, we compared both conventional species data regression and independent contrast regression methods, as well as single trait predictors and a new approach that combines the advantages of a partial least squares (PLS) multivariate regression with independent contrasts. This last approach leverages the predictive power of using multiple correlated proxies. Lastly, we used the rare occurrences of fossil cetaceans with preserved total lengths to test the performance of our predictive equations for reconstructing body size from skull measurements alone. Our results demonstrate that incorporating information about phylogenetic relationships and multiple cranial measures in PLS scaling studies increases the accuracy of reconstructed body size, most notably by reducing prediction intervals by more than 70%. With this empirical foundation, we highlight the outline of major features in the evolution of body size for Neoceti and future opportunities to use these metrics for paleobiological questions.


Cetacea Fossil record Body size Allometry Independent contrasts Partial least squares 



For collections visits and assitance, N. D. P. is most grateful to time and effort of researchers at the following institutions: E. Hoch and staff at the Conservation Department and Gram Museum of Paleontology; D. Long and M. Flannery (CAS); O. Lambert (IRNSB); D. Janiger and J. Dynes (LACM); M. Fornasiero and L. Del Favero (MGPUP); G. Bianucci and C. Sorbini (MSNTUP); C. de Muizon and V. Bouetel (MNHN); C. Conroy and J. Patton (MVZ); R. Sabin, L. Tomsett, and P. Jenkins (NHM); A. van Helden (NMNZ); E. M. G. Fitzgerald (NMV); K. A. Fahy (SBNHM); D. J. Bohaska, C. W. Potter, and J. G. Mead (USNM); and J. Bradley (UWBM). We are also extremely grateful for E. P. J. Heizmann (SMNS), who provided crucial measurements of specimens in Germany. N. D. P. thanks L. G. Barnes and H. Thomas for collections access and assistance at LACM. T. A. Deméré, R. E. Fordyce, J. A. Goldbogen, M. D. Uhen, and J. Velez-Juarbe provided helpful comments, discussions and assistance. We also thank two anonymous reviewers and Editor-in-Chief J. R. Wible for insightful comments that improved the content of this manuscript. This paper represents part of a doctoral dissertation completed by N. D. P. in the Department of Integrative Biology and the Museum of Paleontology at the University of California, Berkeley; input from committee members D. R. Lindberg, A. D. Barnosky, J. H. Lipps, W. Alvarez, and G. J. Vermeij improved the quality of this chapter. C. Nunn, S. Patek, and M. Lahiff also provided valuable support on multivariate comparative methods. Portions of this manuscript were written with funding to N. D. P. from: a National Science Foundation (NSF) Graduate Research Fellowship; a NSF East Asia and Pacific Summer Institutes fellowship, co-sponsored by the Royal Society of New Zealand and the New Zealand Ministry of Science and Technology; the UCMP Remington Kellogg Fund and the Department of Integrative Biology, University of California, Berkeley; a postdoctoral research fellowship from the Natural Sciences and Engineering Research Council of Canada; and from the Smithsonian Institution. Funding for S. N. S. is from the Fannie and John Hertz Foundation.

Supplementary material

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Authors and Affiliations

  1. 1.Department of PaleobiologyNational Museum of Natural History, Smithsonian Institution, NHB MRC 121, 10th and Constitution NWWashingtonUSA
  2. 2.Departments of Mammalogy and PaleontologyBurke Museum of Nature and Culture, University of WashingtonSeattleUSA
  3. 3.Department of BiologyUniversity of WashingtonSeattleUSA

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