Paleobiology

Published by: The Paleontological Society

« previous article : next article »


Paleobiology 29(3):429-454. 2003
doi: 10.1666/0094-8373(2003)029<0429:LTIEWE>2.0.CO;2

Land-to-sea transition in early whales: evolution of Eocene Archaeoceti (Cetacea) in relation to skeletal proportions and locomotion of living semiaquatic mammals

Philip D. Gingerich

Philip D. Gingerich.Department of Geological Sciences and Museum of Paleontology, The University of Michigan, Ann Arbor, Michigan 48109.

Abstract

Skeletal remains of Eocene Archaeoceti provide the only direct and unequivocal evidence of the evolutionary transition of whales from land to sea. Archaeocete skeletons complete enough to be informative about locomotion are rare (principally Rodhocetus and Dorudon), and these deserve to be studied in comparison to the full spectrum of semiaquatic mammals. A principal components analysis of 14 trunk and limb measurements for 50 species of living semiaquatic mammals reduces the observed variation to three informative axes. The first principal axis (PC-I) represents overall size (water mice and shrews have the lowest scores on this axis and the hippopotamus has the highest); the second axis (PC-II) represents a spectrum of aquatic adaptation (seals have the lowest scores and tapirs have the highest); and the third principal axis (PC-III) represents a spectrum ranging from hindlimb- to forelimb-dominated locomotion (sea otters have the lowest scores and the platypus the highest).

Dorudon fits poorly into a morphospace defined solely by living semiaquatic mammals; thus a second 53-species set was analyzed, adding an anthracothere to represent an artiodactyl ancestral morphology and two species of archaeocetes to represent successive stages of early whale evolution. This addition has little effect on the first two principal axes but changes the third substantially. PC-III now represents a contrast of lumbus- (and presumably tail-) dominated versus hindlimb-dominated locomotion (Dorudon has the lowest score and Rodhocetus the highest, whereas the otter shrew has the lowest score among living mammals and the desman the highest). Mammals that are more aquatic have a shorter ilium and femur combined with longer manual and pedal phalanges, whereas the reverse is true for more terrestrial taxa. Lumbus- and tail-dominated swimmers tend to have a longer lumbus combined with shorter pedal elements, whereas the reverse is true for hindlimb-dominated swimmers. Trunk and limb proportions of early middle Eocene Rodhocetus are most similar to those of the living, highly aquatic, foot-powered desmans. Trunk and limb proportions of late middle Eocene Dorudon indicate that it was a lumbus-and-tail-powered swimmer specialized in the direction of modern whales. Thus it appears that the land-to-sea transition in whale evolution involved at least two distinct phases of locomotor specialization: (1) hindlimb domination for drag-based pelvic paddling in protocetids (Rodhocetus), with tail elongation for stability, followed by (2) lumbus domination for lift-based caudal undulation and oscillation in basilosaurids (Dorudon). Rates of evolution in both phases of this change of adaptive zone are about an order of magnitude higher than background rates for the timescale involved.

Accepted: January 24, 2003



Literature Cited

Allen, J. A. 1880. History of North American pinnipeds: a monograph of the walruses, sea-lions, sea-bears, and seals of North America. In U.S. Geological and Geographical Survey of the Territories, F. V. Hayden, Geologist-in-Charge,. Miscellaneous Publications 12:1–785.
Bajpai, S. and P. D. Gingerich. 1998. A new Eocene archaeocete (Mammalia, Cetacea) from India and the time of origin of whales. Proceedings of the National Academy of Sciences USA 95:15464–15468. CrossRef, PubMed, CSA
Berggren, W. A., D. V. Kent, C. C. Swisher, and M-P. Aubry. 1995. A revised Cenozoic geochronology and chronostratigraphy. In W. A. Berggren, D. V. Kent, M.-P. Aubry, and J. A. Hardenbol, eds. Geochronology, time scales and global stratigraphic correlations: a unified temporal framework for an historical geology. Society of Economic Paleontologists and Mineralogists, Special Volume 54:129–212.
Darwin, C. 1859. On the origin of species by means of natural selection or the preservation of favoured races in the struggle for life. J. Murray, London.
Dobson, G. E. 1882. A monograph of the Insectivora, systematic and anatomical. Van Voorst, London.
Eisenberg, J. F. 1981. The mammalian radiations: an analysis of trends in evolution, adaptation, and behavior. University of Chicago Press, Chicago.
Fish, F. E. 1982. Function of the compressed tail of surface swimming muskrats (Ondatra zibethicus). Journal of Mammalogy 63:591–597. CrossRef, CSA
Fish, F. E. 1996. Transitions from drag-based to lift-based propulsion in mammalian swimming. American Zoologist 36:628–641.
Fish, F. E. 2000. Biomechanics and energetics in aquatic and semiaquatic mammals: platypus to whale. Physiological and Biochemical Zoology 73:683–698. CrossRef, PubMed
Fish, F. E. 2001. A mechanism for evolutionary transition in swimming mode by mammals. Pp. 261–287 in J.-M. Mazin and V. d. Buffrénil, eds. Secondary adaptation of tetrapods to life in water. Friedrich Pfeil, Munich.
Flower, W. H. 1883a. On whales, past and present, and their probable origin. Notices of the Proceedings of the Royal Institution of Great Britain, London 10:360–376.
Flower, W. H. 1883b. Cetacea. Pp. 391–400 in T. S. Baynes, ed. Encyclopaedia Britannica, 9th ed. A. and C. Black, Edinburgh.
Fordyce, R. E. and L. G. Barnes. 1994. The evolutionary history of whales and dolphins. Annual Review of Earth and Planetary Sciences 22:419–455. CrossRef, CSA
Fordyce, R. E. and C. de Muizon. 2001. Evolutionary history of cetaceans: a review. Pp. 169–233 in J.-M. Mazin and V. de Buffrénil, eds. Secondary adaptation of tetrapods to life in water. Friedrich Pfeil, Munich.
Fraas, E. 1904. Neue Zeuglodonten aus dem unteren Mitteleocän vom Mokattam bei Cairo. Geologische und Paläontologische Abhandlungen, Jena 6:197–220.
Gingerich, P. D. 1992. Marine mammals (Cetacea and Sirenia) from the Eocene of Gebel Mokattam and Fayum, Egypt: stratigraphy, age, and paleoenvironments. University of Michigan Papers on Paleontology 30:1–84.
Gingerich, P. D. 1998. Paleobiological perspectives on Mesonychia, Archaeoceti, and the origin of whales. Pp. 423–449 in J. G. M. Thewissen, ed. Emergence of whales: evolutionary patterns in the origin of Cetacea. Plenum, New York.
Gingerich, P. D. 2000. Arithmetic or geometric normality of biological variation: an empirical test of theory. Journal of Theoretical Biology 204:201–221. CrossRef, PubMed, CSA
Gingerich, P. D. 2001. Rates of evolution on the time scale of the evolutionary process. In A. P. Hendry and M. T. Kinnison, eds. Contemporary microevolution: rate, pattern, and process. Genetica 112:/113. 127–144. CrossRef, PubMed, CSA
Gingerich, P. D. 2003. Stratigraphic and micropaleontologic constraints on the middle Eocene age of the mammal-bearing Kuldana Formation of Pakistan. Journal of Vertebrate Paleontology (in press).
Gingerich, P. D. and D. E. Russell. 1981. Pakicetus inachus, a new archaeocete (Mammalia, Cetacea) from the early-middle Eocene Kuldana Formation of Kohat (Pakistan). Contributions from the Museum of Paleontology, University of Michigan 25:235–246.
Gingerich, P. D. and M. D. Uhen. 1996. Ancalecetus simonsi, a new dorudontine archaeocete (Mammalia, Cetacea) from the early late Eocene of Wadi Hitan, Egypt. Contributions from the Museum of Paleontology, University of Michigan 29:359–401.
Gingerich, P. D. 1998. Likelihood estimation of the time of origin of Cetacea and the time of divergence of Cetacea and Artiodactyla. Palaeontologia Electronica 1:21–45. [http//palaeo-electronica.org/1998_2/ging_uhen/issue2.htm].
Gingerich, P. D., N. A. Wells, D. E. Russell, and S. M I. Shah. 1983. Origin of whales in epicontinental remnant seas: new evidence from the early Eocene of Pakistan. Science 220:403–406. CrossRef, PubMed, CSA
Gingerich, P. D., B. H. Smith, and E. L. Simons. 1990. Hind limbs of Eocene Basilosaurus isis: evidence of feet in whales. Science 249:154–157. CrossRef, PubMed, CSA
Gingerich, P. D., S. M. Raza, M. Arif, M. Anwar, and X. Zhou. 1994. New whale from the Eocene of Pakistan and the origin of cetacean swimming. Nature 368:844–847. CrossRef, CSA
Gingerich, P. D., M. Haq, I. S. Zalmout, I. H. Khan, and M. S. Malkani. 2001a. Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan. Science 293:2239–2242. CrossRef, PubMed, CSA
Gingerich, P. D., M. Haq, I. H. Khan, and I. S. Zalmout. 2001b. Eocene stratigraphy and archaeocete whales (Mammalia, Cetacea) of Drug Lahar in the eastern Sulaiman Range, Balochistan (Pakistan). Contributions from the Museum of Paleontology, University of Michigan 30:269–319.
Hearne, S. 1795. A journey from Prince of Wale's fort, in Hudson's Bay, to the northern ocean. A. Strahan and T. Cadell, London.
Heyning, J. E. and G. M. Lento. 2002. The evolution of marine mammals. Pp. 38–72 in A. R. Hoelzel, ed. Marine mammal biology. Blackwell Scientific, Oxford.
Hickman, G. C. 1983. Influence of the semiaquatic habit in determining burrow structure of the star-nosed mole (Condylura cristata). Canadian Journal of Zoology 61:1688–1692. CrossRef
Howell, A. B. 1930. Aquatic mammals. Charles C. Thomas, Springfield, Ill.
Hulbert, R. C., R. M. Petkewich, G. A. Bishop, D. Bukry, and D. P. Aleshire. 1998. A new middle Eocene protocetid whale (Mammalia: Cetacea: Archaeoceti) and associated biota from Georgia. Journal of Paleontology 72:907–927. CSA
Kellogg, R. 1936. A review of the Archaeoceti. Carnegie Institution of Washington Publications 482:1–366.
Kron, D. G. and E. M. Manning. 1998. Anthracotheriidae. Pp. 381–388 in C. M. Janis, K. M. Scott, and L. L. Jacobs, eds. Evolution of Tertiary mammals of North America, Vol. I. Terrestrial carnivores, ungulates, and ungulatelike mammals. Cambridge University Press, Cambridge.
Kükenthal, W. G. 1890. Ueber die Anpassung von Saügethieren an das Leben im Wasser. Zoologische Jahrbücher, Abteilung für Systematik, Geographie, und Biologie der Tiere, Jena 5:373–399.
Kükenthal, W. G. 1891. On the adaptation of mammals to aquatic life. Annals and Magazine of Natural History 7:153–179.
Lewontin, R. C. 1966. On the measurement of relative variability. Systematic Zoology 15:141–142. CrossRef
Luo, Z. and P. D. Gingerich. 1999. Terrestrial Mesonychia to aquatic Cetacea: transformation of the basicranium and evolution of hearing in whales. University of Michigan Papers on Paleontology 31:1–98.
Madar, S. I., J. G M. Thewissen, and S. T. Hussain. 2002. Additional holotype remains of Ambulocetus natans (Cetacea, Ambulocetidae), and their implications for locomotion in early whales. Journal of Vertebrate Paleontology 22:405–422. CrossRef, CSA
Manly, B. F J. 1994. Multivariate statistical methods: a primer, 2d ed. Chapman and Hall, London.
Nishiwaki, M. and T. Kamiya. 1959. Mesoplodon stejnegeri from the coast of Japan. Scientific Reports of the Whales Research Institute, Tokyo 14:35–48.
Nowak, R. M. 1999. Walker's mammals of the world, 6th ed. Vols. 1, 2. Johns Hopkins University Press, Baltimore.
Omura, H. 1975. Osteological study of the minke whale from the Antarctic. Scientific Reports of the Whales Research Institute, Tokyo 27:1–36.
Osburn, R. C. 1903. Adaptation to aquatic, arboreal, fossorial and cursorial habits in mammals. I. Aquatic adaptations. American Naturalist 37:651–665. CrossRef
Palmeirim, J. M. and R. S. Hoffmann. 1983. Galemys pyrenaicus. Mammalian Species 207:1–5. CrossRef
Piérard, J. 1971. Osteology and myology of the Weddell seal Leptonychotes weddelli (Lesson, 1826). In W. H. Burt, ed. Antarctic Pinnipedia. Antarctic Research Series 18:53–108.
Press, W. H., B. P. Flannery, S. A. Teukolsky, and W. T. Vetterling. 1989. Numerical recipes: the art of scientific computing (Fortran version). Cambridge University Press, Cambridge.
Scott, W. B. 1894. The structure and relationships of Ancodus. Journal of the Academy of Natural Sciences of Philadelphia 9:461–497.
Scott, W. B. 1940. The mammalian fauna of the White River Oligocene, Part IV. Artiodactyla. Transactions of the American Philosophical Society 28:363–746. CrossRef
Simpson, G. G. 1944. Tempo and mode in evolution. Reprint, 1984, Columbia University Press, New York.
Stein, B. R. 1988. Morphology and allometry in several genera of semiaquatic rodents (Ondatra, Nectomys, and Oryzomys). Journal of Mammalogy 69:500–511. CrossRef
Thewissen, J. G M. and F. E. Fish. 1997. Locomotor evolution in the earliest cetaceans: functional model, modern analogues, and paleontological evidence. Paleobiology 23:482–490.
Thewissen, J. G M. and S. T. Hussain. 1993. Origin of underwater hearing in whales. Nature 361:444–445. CrossRef, PubMed, CSA
Thewissen, J. G M. and E. M. Williams. 2002. The early radiations of Cetacea (Mammalia): evolutionary pattern and developmental correlations. Annual Review of Ecology and Systematics 33:73–90. CrossRef
Thewissen, J. G M., S. T. Hussain, and M. Arif. 1994. Fossil evidence for the origin of aquatic locomotion in archaeocete whales. Science 263:210–212. CrossRef, PubMed, CSA
Thewissen, J. G M., S. I. Madar, and S. T. Hussain. 1996. Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan. Courier Forschungsinstitut Senckenberg 191:1–86.
Thewissen, J. G M., E. M. Williams, L. J. Roe, and S. T. Hussain. 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature 413:277–281. CrossRef, PubMed, CSA
Uhen, M. D. 1996. Dorudon atrox (Mammalia, Cetacea): form, function, and phylogenetic relationships of an archaeocete from the late middle Eocene of Egypt. Ph.D. dissertation, University of Michigan, Ann Arbor.
Uhen, M. D. 1998. Middle to late Eocene basilosaurines and dorudontines. Pp. 29–61 in J. G. M. Thewissen, ed. The emergence of whales: evolutionary patterns in the origin of Cetacea. Plenum, New York.
Uhen, M. D. 1999. New species of protocetid archaeocete whale, Eocetus wardii (Mammalia: Cetacea) from the middle Eocene of North Carolina. Journal of Paleontology 73:512–528.
Uhen, M. D. 2003. Form, function, and anatomy of Dorudon atrox (Mammalia, Cetacea): an archaeocete from the middle to late Eocene of Egypt. University of Michigan Papers on Paleontology 34 (in press).
Voss, R. S. 1988. Systematics and ecology of ichthyomyine rodents (Muroidea): patterns of morphological evolution in a small adaptive radiation. Bulletin of the American Museum of Natural History 188:260–493.
Wolff, J. O. and R. D. Guthrie. 1985. Why are aquatic small mammals so large? Oikos 45:365–373. CrossRef, CSA
Yablokov, A. V. 1974. Variability of mammals. Amerind, New Delhi.
Yamada, M. 1954. An account of a rare porpoise Feresa Gray from Japan. Scientific Reports of the Whales Research Institute, Tokyo 9:59–88.

Figure 1. Skeleton of the semiaquatic Russian desman or aquatic mole Desmana moschata. A, Drawing reproduced from Dobson (1882); note relatively short femur and long hind foot. B, Schematic shows fourteen lengths of trunk and limb segments measured here (see Table 4); measurements were made on original skeletons (see Appendix for list of specimens)

Figure 2. Skeletons of semiaquatic mammals transitional from land to sea in the origin of whales. A, Hippo-like early Oligocene anthracothere artiodactyl Elomeryx armatus assumed to represent a Paleocene-to-early Eocene stage of cetacean evolution. B, Early middle Eocene archaeocete Rodhocetus balochistanensis (tail length not known) representing an early middle Eocene protocetid stage of cetacean evolution. C, Middle-to-late Eocene archaeocete Dorudon atrox representing a middle-to-late Eocene basilosaurid stage of cetacean evolution. Elomeryx restoration is from Scott (1894), Rodhocetus restoration is from Gingerich et al. (2001a), and Dorudon restoration is from Gingerich and Uhen (1996). Skeletons are drawn at comparable sizes, not to scale (see Appendix for measurements)

Figure 3. Fifty-species principal components analysis of trunk and limb lengths of living semiaquatic mammals. A, Bivariate plot of PC-I versus PC-II, with related taxonomic groups enclosed in shaded convex polygons. B, Univariate plot of eigenvector coefficients or loadings for PC-I. C, Univariate plot of eigenvector coefficients or loadings for PC-II. PC-I is an axis of general size separating species in a spectrum from small (at left) to large (at right). Note that loadings for PC-I are all similar and positive. PC-II is an axis of aquatic adaptation separating mammals that are more aquatic (below) from those that are more terrestrial (above). Note that loadings for PC-II contrast long manual and pedal phalanges (Pedpiii2, Manpiii2, Pedpiii1, Manpiii1) in species that are more aquatic versus a long ilium and femur (Ilium, Femur) in species that are more terrestrial. Open diamonds labeled R.b. and D.a. show positions of Rodhocetus balochistanensis and Dorudon atrox, respectively, projected into this morphometric space based on living semiaquatic mammals. Neither taxon is particularly similar to river otters (cross-hatched) or to the sea otter (En.lu.). Remaining abbreviations are listed in Tables 4 and 5

Figure 4. Fifty-species principal components analysis of trunk and limb lengths of living semiaquatic mammals. A, Bivariate plot of PC-III versus PC-II, with related taxonomic groups enclosed in shaded convex polygons. B, Univariate plot of eigenvector coefficients or loadings for PC-II. C, Univariate plot of eigenvector coefficients or loadings for PC-III. PC-II is an axis of aquatic adaptation separating mammals that are more aquatic (below) from those that are more terrestrial (above). Note that loadings for PC-II contrast long manual and pedal phalanges (Pedpiii2, Manpiii2, Pedpiii1, Manpiii1) in mammals that are more aquatic versus a long ilium and femur (Ilium, Femur) in mammals that are more terrestrial. PC-III is an axis of locomotor specialization separating species that are hindlimb dominated (left) from those that are forelimb dominated (right). Note that loadings for PC-III contrast a long lumbus, metatarsal III, and pedal phalanx III-1 (Lumbus, Mtarsiii, Pedpiii1) in species that are more hindlimb dominated versus long manual phalanges and metacarpal III (Manpiii1, Manpiii2, Mcarpiii) in species that are more forelimb dominated. Open diamonds labeled R.b. and D.a. show positions of Rodhocetus balochistanensis and Dorudon atrox, respectively, projected into this morphometric space based on living semiaquatic mammals. Neither taxon is particularly similar to river otters (cross-hatched) or to the sea otter (En.lu.). Remaining abbreviations are listed in Tables 4 and 5.

Figure 5. Fifty-three-species principal components analysis of trunk and limb lengths of living semiaquatic mammals plus three fossil taxa: Elomeryx armatus (E.a.), Rodhocetus balochistanensis (R.b.), and Dorudon atrox (D.a.). A, Bivariate plot of PC-I versus PC-II, with related taxonomic groups enclosed in shaded convex polygons. B, Univariate plot of eigenvector coefficients or loadings for PC-I. C, Univariate plot of eigenvector coefficients or loadings for PC-II. PC-I is an axis of general size separating species in a spectrum from small (at left) to large (at right). Note that loadings for PC-I are all similar and positive. PC-II is an axis of aquatic adaptation separating mammals that are more aquatic (below) from those that are more terrestrial (above). Note that loadings for PC-II contrast long manual and pedal phalanges (Manpiii2, Pedpiii2, Pedpiii1, Manpiii1) in species that are more aquatic versus a long ilium and femur (Ilium, Femur) in species that are more terrestrial. None of the fossil taxa (diamonds) is particularly similar to river otters (cross-hatched) or to the sea otter (En.lu.). Remaining abbreviations are listed in Tables 4 and 5. Eigenvector coefficients differ slightly from those in 50-species analysis, and the position of Dorudon atrox is different (diamond D.a.), but otherwise this figure is little changed from Figure 3. Possible position of Ambulocetus natans is shown by an open diamond (Am.na.?; see text)

Figure 6. Fifty-three-species principal components analysis of trunk and limb lengths of living semiaquatic mammals plus three fossil taxa: Elomeryx armatus (E.a.), Rodhocetus balochistanensis (R.b.), and Dorudon atrox (D.a.). A, Bivariate plot of PC-III versus PC-II, with related taxonomic groups enclosed in shaded convex polygons. B, Univariate plot of eigenvector coefficients or loadings for PC-II. C, Univariate plot of eigenvector coefficients or loadings for PC-III. PC-II is an axis of aquatic adaptation separating mammals that are more aquatic (below) from those that are more terrestrial (above). Note that loadings for PC-II contrast long manual and pedal phalanges (Manpiii2, Pedpiii2, Pedpiii1, Manpiii1) in mammals that are more aquatic versus a long ilium and femur (Ilium, Femur) in mammals that are more terrestrial. PC-III is an axis of locomotor specialization separating species that are lumbus dominated (left) from those that are hindlimb dominated (right). Note that loadings for PC-III contrast a long lumbus (Lumbus) in species that are more lumbus dominated versus a long pedal phalanx III-2 (Pedpiii2) in species that are more hindlimb dominated. None of the fossil taxa (diamonds) is particularly similar to river otters (cross-hatched) or to the sea otter (En.lu.). Remaining abbreviations are listed in Tables 4 and 5. The vertical aquatic versus terrestrial axis is little changed from that of the 50-species analysis shown in Figure 4, but the horizontal locomotor axis was substantially reorganized when the fossil taxa, particularly Dorudon atrox (diamond D.a.), were added. Possible position of Ambulocetus natans is shown by an open diamond (Am.na.?; see text)

Figure 7. Evolutionary trajectory of early whale evolution from an artiodactyl land-mammal ancestor at ca. 55 Ma, represented morphologically by Elomeryx armatus, to semiaquatic Rodhocetus balochistanensis at ca. 47.5 Ma, to fully-aquatic Dorudon atrox retaining hindlimbs and feet at 37 Ma. Trajectory is graphed on the bivariate plot of PC-III versus PC-II in the 53-species analysis of Figure 6. Note that the successive fossil taxa show a progression of increasing aquatic adaptation moving from the top to the bottom of the diagram. However, they simultaneously show an abrupt reversal on the locomotor axis, moving first to extreme hindlimb domination (right) and then to extreme lumbus domination (left). Axes are calibrated in natural log (ln) units externally and corresponding standard deviation units internally (employing generally observed 5% coefficient of variation for linear measurements; see text). Inset box shows rates of evolution calculated for the first or Elomeryx to Rodhocetus transition and for the second or Rodhocetus to Dorudon transition, based on 14 measurements of each (A), based on PC-I, PC-II, and PC-III individually (B), and based on PC-I, PC-II, and PC-III simultaneously (C). Sample sizes are given in parentheses. All rates are calculated in standard deviation units on a 1,500,000 or 106.18 generation timescale. Solid circles represent positive rates and open circles negative rates. All but one of the rates calculated here exceeds the rate of 10−6.36 (dashed line) expected for paleontological rates calculated on such long time scales (Gingerich 2001: p. 139). Note that multivariate rates here are higher than the average for univariate rates, and rates for the second or Rodhocetus to Dorudon transition are higher than corresponding rates for the first or Elomeryx to Rodhocetus transition

table

Appendix Measurements of trunk and limb lengths for 50 species of living semiaquatic mammals and three species known from fossils, including archaeocetes Rodhocetus balochistanensis and Dorudon atrox, documenting the transition from land to sea in early whale evolution. Male (M) and female (F) specimens were averaged (geometric mean) when both (B) were available. Abbreviations: MCZ, Museum of Comparative Zoology, Harvard University, Cambridge; L-, Natural History Museum, London; UMMP, University of Michigan Museum of Paleontology, Ann Arbor; UMMZ, University of Michigan Museum of Zoology, Ann Arbor

table

Appendix. Continued

table

Table 1. Classification of genera in five families of Archaeoceti (bold). Summary of known skeletal remains is provided in the right-hand column. Skeletons of Rodhocetus and Dorudon are sufficiently complete and generalized to be included in the analysis presented here

table

Table 2. Summary classification and common names of living semiaquatic mammals studied here (measurements are listed in the Appendix). Columns He, K, O, Ho, W, and V refer to Hearne (1795), Kükenthal (1890, 1891), Osburn (1903), Howell (1930), Wolff and Guthrie (1985), Voss (1988), respectively, and Xs mark species included by each as semiaquatic. Dashes mark species identified as semiaquatic that are not mentioned by a subsequent author. Column N refers to Nowak (1999) and gives page number of entry in this general reference

table

Table 2. Continued

table

Table 3. Nine orders and 17 families of living mammals containing semiaquatic species. Skeletons of 50 out of 124 species were measured, including representatives of all orders and families. Most of the species that were not available for measurement are small shrews (Insectivora) and murids (Rodentia)

table

Table 4. Fourteen measurements representing trunk and limb segments of semiaquatic mammals. Schematic diagram showing measurements is included in Figure 1

table

Table 5. Principal components scores by species for PC-I, PC-II, and PC-III in (1) an analysis of 50 species of living semiaquatic mammals excluding fossil taxa; and (2) an analysis of all 53 semiaquatic species considered here (50 species of living mammals plus three fossil taxa Elomeryx armatus, Rodhocetus balochistanensis, and Dorudon atrox). PC scores for fossil taxa added to 50-species analysis are enclosed in parentheses

table

Table 6. Eigenvalues and eigenvector coefficients associated with each principal component (PC) based on 50 living semiaquatic mammals. Scores for an additional species like Rodhocetus balochistanensis are determined by summing products of the appropriate eigenvector coefficient here multiplied by (xi − mi)/si over all i = 14 measurements, where xi is the vector of ln-transformed measurements, mi is the corresponding 50-species mean from the bottom of the table, and si is the corresponding 50-species standard deviation from the bottom of the table. Results for principal components I, II, and III are shown graphically in Figures 3 and 4

table

Table 7. Eigenvalues and eigenvector coefficients associated with each principal component based on 50 living semiaquatic mammals plus three extinct taxa, Elomeryx armatus, Rodhocetus balochistanensis, and Dorudon atrox. Scores for an additional species would be determined by summing products of the appropriate eigenvector coefficient here multiplied by (xi − mi)/si over all i = 14 measurements, where xi is the vector of ln-transformed measurements, mi is the corresponding 53-species mean from the bottom of the table, and si is the corresponding 53-species standard deviation from the bottom of the table. Results for principal components I, II, and III are shown graphically in Figures 5 and 6

Cited by

Joshua X. Samuels, Blaire Van Valkenburgh. (2008) Skeletal indicators of locomotor adaptations in living and extinct rodents. Journal of Morphology 269:11, 1387-1411
Online publication date: 1-Dec-2008.
CrossRef
Ryan M. Bebej. (2008) Swimming Mode Inferred from Skeletal Proportions in the Fossil Pinnipeds Enaliarctos and Allodesmus (Mammalia, Carnivora). Journal of Mammalian Evolution
Online publication date: 3-Nov-2008.
CrossRef
Natalia Rybczynski. (2008) Woodcutting behavior in beavers (Castoridae, Rodentia): estimating ecological performance in a modern and a fossil taxon. Paleobiology 34:3, 389-402
Online publication date: 1-Sep-2008.

Abstract & References : Full Text : PDF (549 KB) : Rights & Permissions 

RACHEL H. DUNN, D. TAB RASMUSSEN. (2007) SKELETAL MORPHOLOGY AND LOCOMOTOR BEHAVIOR OF PSEUDOTOMUS EUGENEI (RODENTIA, PARAMYINAE) FROM THE UINTA FORMATION, UTAH. Journal of Vertebrate Paleontology 27:4, 987-1006
Online publication date: 1-Dec-2007.

Abstract & References : Full Text : PDF (1752 KB) : Rights & Permissions 

KEVIN J. PETERSON, ROGER E. SUMMONS, PHILIP C. J. DONOGHUE. (2007) MOLECULAR PALAEOBIOLOGY. Palaeontology 50:4, 775-809
Online publication date: 1-Aug-2007.
CrossRef
SIRPA NUMMELA, S. TASEER HUSSAIN, J. G. M. THEWISSEN. (2006) CRANIAL ANATOMY OF PAKICETIDAE (CETACEA, MAMMALIA). Journal of Vertebrate Paleontology 26:3, 746-759
Online publication date: 1-Sep-2006.

Abstract & References : Full Text : PDF (2323 KB) : Rights & Permissions 

JONATHAN H. GEISLER, ALBERT E. SANDERS, ZHE-XI LUO. (2005) A New Protocetid Whale (Cetacea: Archaeoceti) from the Late Middle Eocene of South Carolina. American Museum Novitates 1-68
Online publication date: 1-Jul-2005.

Abstract & References : Full Text : PDF (1954 KB) : Rights & Permissions 

Philip D. Gingerich. (2005) Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian Desmostylus. Journal of Mammalian Evolution 12:1-2, 183-194
Online publication date: 1-Jul-2005.
CrossRef
Sirpa Nummela, J. G. M. Thewissen, Sunil Bajpai, S. Taseer Hussain, Kishor Kumar. (2004) Eocene evolution of whale hearing. Nature 430:7001, 776-778
Online publication date: 12-Sep-2004.
CrossRef
 
BioOne is the product of innovative collaboration between scientific societies, libraries, academe and the private sector.
 
21 Dupont Circle NW, Suite 800, Washington, DC 20036 • Phone 202.296.2296 • Fax 202.872.0884
 
Copyright © 2009 BioOne All rights reserved