Hostname: page-component-8448b6f56d-gtxcr Total loading time: 0 Render date: 2024-04-17T03:54:14.068Z Has data issue: false hasContentIssue false
  • English
  • Français

Fossil horses from “Eohippus” (Hyracotherium) to Equus: scaling, Cope's Law, and the evolution of body size

Published online by Cambridge University Press:  08 April 2016

Bruce J. MacFadden
Bruce J. MacFadden*
Affiliation:
Florida State Museum, University of Florida, Gainesville, Florida 32611
Get access Rights & Permissions [Opens in a new window]

Abstract

The evolution of body size in fossil horses is frequently depicted as a gradual, progressive trend toward increased body size (Cope's Law). Body size (actually body mass) was estimated for 40 species of fossil horses using dental and skeletal characters and regression equations derived from the same characters in extant species of Equus with known body mass. After body sizes were estimated, rates of morphological evolution, in darwins (d), were calculated between known ancestral and descendant fossil horse species. For the first half of horse evolution (from ca. 57 to 25 ma) body mass remained relatively static between about 25 and 50 kg with very slow evolutionary rates of 0.003–0.04 d. During the early–middle Miocene (from ca. 25 to 10 ma) there was a major diversification of body mass to about 75–400 kg and consistently higher evolutionary rates between 0.04 and 0.24 d. Since the late Miocene, body mass has generally increased with a maximum seen (in natural populations) in Equus scotti (ca. 500 kg) during the middle Pleistocene. Therefore, for horses, the traditional interpretation of gradual increase in body size through time is oversimplified because: (1) although the exception to the rule, 5 of 24 species lineages studied are characterized by dwarfism; and (2) the general trend seems to have been a long period (32 ma) of relative stasis followed by 25 ma of diversification and progressive (although not necessarily gradual) change in body size.

Type
Articles
Information
Paleobiology , Volume 12 , Issue 4 , Fall 1986 , pp. 355 - 369
Copyright
Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Literature Cited

Anderson, A. E., Frary, L. G., and Stewart, R. H. 1964. A comparison of three morphological attributes of muledeer from the Guadalupe and Sacramento mountains, New Mexico. J. Mammal. 45:48–53.CrossRefGoogle Scholar
Berggren, W., Kent, D. V., and Flynn, J. J. 1985. Cenozoic geochronology and chronostratigraphy. Bull. Geol. Soc. Am. 96:1407–1418.Google Scholar
Blakely, R. L. 1985. Miniature horses. Nat. Geogr. 167:384–393.Google Scholar
Creighton, G. K. 1980. Static allometry of mammalian teeth and the correlation of tooth size and body size in contemporary mammals. J. Zool. London. 191:435–443.Google Scholar
Damuth, J. D. 1981a. Population density and body size in mammals. Nature. 290:699–700.Google Scholar
Damuth, J. D. 1981b. Home range, home range overlap, and species energy use among herbivorous mammals. Biol. J. Linnean Soc. 15:185–193.CrossRefGoogle Scholar
Damuth, J. D. 1982. The evaluation of the degree of community structure preserved in assemblages of fossil mammals. 248 pp. Ph. D. diss., Univ. Chicago.Google Scholar
DeBlase, A. F. and Martin, R. E. 1981. A Manual of Mammalogy with Keys to Families of the World. Wm. C. Brown Co. Pub.; Dubuque. 436 pp.Google Scholar
Dhaliwal, S. S. 1962. Studies on body measurements and skeletal variations of two taxa of Rattus rattus in Malaya. J. Mammal. 43:249–261.Google Scholar
Drapier, N. and Smith, H. 1966. Applied Regression Analysis. John Wiley & Sons, Inc.; New York. 407 pp.Google Scholar
Eisenberg, J. F. 1981. The Mammalian Radiations: An Analysis of Trends in Evolution, Adaptation, and Behavior. Univ. Chicago Press; Chicago. 610 pp.Google Scholar
Gingerich, P. D. 1982. Time resolution in mammalian evolution: sampling, lineages, and faunal turnover. Proc. 3d N. Am. Paleontol. Conv. 1:205–210.Google Scholar
Gingerich, P. D. 1983. Rate of evolution: effects of time and temporal scaling. Science. 222:159–161.CrossRefGoogle Scholar
Gingerich, P. D. 1984. Smooth curve of evolutionary rate: a psychological and mathematical artifact. [Reply to Gould] Science. 226:995–996.Google Scholar
Gingerich, P. D., Smith, B. H., and Rosenberg, K. 1982. Allometric scaling in the dentition of primates and prediction of body weight from tooth size in fossils. Am. J. Phys. Anthropol. 58:81–100.Google Scholar
Gould, S. J. 1975. On the scaling of tooth size in mammals. Am. Zool. 15:351–362.Google Scholar
Gould, S. J. 1984. Gingerich's smooth curve of evolutinary rate: a psychological and mathematical artifact. Science. 226:994–995.Google Scholar
Haldane, J. B. S. 1949. Suggestions as to quantitative measurements of rates of evolution. Evolution. 3:51–56.CrossRefGoogle ScholarPubMed
Hanney, P. and Morris, B. 1962. Some observations upon the pouched rat in Nyasaland. J. Mammal. 43:238–247.Google Scholar
Hulbert, R. C. Jr. 1982. Population dynamics of the three-toed horse Neohipparion from the late Micoene of Florida. Paleobiology. 8:159–167.Google Scholar
Hulbert, R. C. Jr. 1985. Paleoecology and population dynamics of the early Miocene (Hemingfordian) horse Parahippus leonensis from the Thomas Farm site, Florida. J. Vert. Paleontol. 4:547–558.Google Scholar
Janis, C. 1982. Evolution of horns in ungulates: ecology and palaecology. Biol. Rev., Cambridge Phil. Soc. 57:261–318.Google Scholar
Jarman, P. J. 1974. The social organization of antelope in relation to their ecology. Behaviour. 48:215–267.Google Scholar
Kay, R. and Simons, E. L. 1980. The ecology of Oligocene African Anthropoidea. Int. J. Primatol. 1:21–37.Google Scholar
Kiltie, R. A. 1984. Seasonality, gestation time, and large mammal extinctions. Pp. 299–314. In: Martin, P. S. and Klein, R. G., eds. Quaternary Extinctions: A Prehistoric Revolution. Univ. Arizona Press; Tucson. 891 pp.Google Scholar
Kleiber, M. 1961. The Fire of Life. John Wiley & Sons; New York. 454 pp.Google Scholar
Kramer, A. W. 1964. Body and organ weights and linear measurements of the adult Mongolian Gerbil. Anat. Rec. 150:343–349.Google Scholar
Kruuk, H. 1972. The Spotted Hyaena: A Study of Predation and Social Behavior. Univ. Chicago Press; Chicago. 335 pp.Google Scholar
Latimer, H. B. 1936. Weight and linear measurements of the adult cat. Am. J. Anat. 58:329–347.CrossRefGoogle Scholar
Ledger, H. P. 1963. Weights of some East African mammals. East African J. Ecol. 1:123–124.CrossRefGoogle Scholar
MacFadden, B. J. 1984. Systematics and phylogeny of Hipparion, Neohipparion, Nannippus, and Cormohipparion (Mammalia, Equidae) from the Miocene and Pliocene of the New World. Bull. Am. Mus. Nat. Hist. 179:1–196.Google Scholar
MacFadden, B. J. 1985. Patterns of phylogeny and rates of evolution in fossil horses: hipparions from the Miocene and Pliocene of North America. Paleobiology. 11:245–257.Google Scholar
MacFadden, B. J. In press. Character variation in fossil horses (Equidae): a test of the paleopopulation and morphospecies concepts. In: Redford, K. E. and Eisenberg, J. F., eds. Ralph Wetzel Memorial Volume.Google Scholar
MacFadden, B. J. In prep. Fossil horses from “Eohippus” (Hyracotherium) to Equus: rates of dental evolution revisited.Google Scholar
Martin, R. A. 1980. Body mass and basal metabolism of extinct mammals. Comp. Biochem. Physiol. 66:307–314.CrossRefGoogle Scholar
McNab, B. K. 1963. Bioenergetics and the determination of home range. Am. Nat. 97:133–140.Google Scholar
Pianka, E. R. 1974. Evolutionary Ecology. Harper & Row; New York. 356 pp.Google Scholar
Radinsky, L. B. 1969. The early evolution of the Perissodactyla. Evolution. 23:308–328.Google Scholar
Radinsky, L. B. 1978. Evolution of brain size in carnivores and ungulates. Am. Nat. 112:815–831.CrossRefGoogle Scholar
Radinsky, L. B. 1982. Some cautionary notes on making inferences about relative brain size. Pp. 29–37. In: Armstrong, E. and Falk, D., eds. Primate Brain Evolution: Methods and Concepts. Plenum Pub. Corp.; New York.Google Scholar
Robinson, J. G. and Redford, K. H. In press. Body size, diet, and population density of Neotropical forest mammals. In: Redford, K. E. and Eisenberg, J. F., eds. Ralph Wetzel Memorial Volume.Google Scholar
Sachs, R. 1967. Liveweights and body measurements of Serengeti game animals. E. Afr. J. Ecol. 5:24–36.Google Scholar
Simpson, G. G. 1953. The Major Features of Evolution. Columbia Univ. Press; New York. 434 pp.Google Scholar
Simpson, G. G., Roe, A., and Lewontin, R. C. 1960. Quantitative Zoology. Harcourt, Brace & Co.; San Francisco. 440 pp.Google Scholar
Sokal, R. R. and Rohlf, F. J. 1981. Biometry: The Principles and Practice of Statistics in Biological Research. W. H. Freeman; San Francisco. 859 pp.Google Scholar
Stanley, S. M. 1979. Macroevolution: Pattern and Process. W. H. Freeman; San Francisco. 332 pp.Google Scholar
Stanley, S. M. 1985. Rates of evolution. Paleobiology. 11:13–26.Google Scholar
Stirton, R. A. 1940. Phylogeny of North American Equidae. Univ. California Publ., Bull. Dept. Geol. Sci. 25:165–198.Google Scholar
Tedford, R. H., Galusha, T., Skinner, M. F., Taylor, B. E., Fields, R. W., Macdonald, J. R., Rensberger, J. M., Webb, S. D., and Whistler, D. P.Faunal succession and biochronology of the Arikareean through Hemphillian interval (Late Oligocene through Late Miocene epochs), North America. In: Woodburne, M. O., ed. Vertebrate Paleontology as a Discipline in Geochronology. Univ. California Press; Berkeley. In press.Google Scholar
Thomason, J. J. 1985. Estimation of locomotory forces and stresses in the limb bones of Recent and extinct equids. Paleobiology. 11:209–220.Google Scholar
Walker, E. P. 1968. Mammals of the World. Johns Hopkins Univ. Press; Baltimore. 1,500 pp.Google Scholar
Yablokov, A. V. 1974. Variability of Mammals. Amerind Pub. Co. Pvt. Ltd.; New Delhi. 350 pp.Google Scholar