The Evolution of Maximum Body Size of Terrestrial Mammals

  title={The Evolution of Maximum Body Size of Terrestrial Mammals},
  author={Felisa A. Smith and Alison G. Boyer and James H. Brown and Daniel P. Costa and Tamar Dayan and S. K. Morgan Ernest and Alistair R. Evans and Mikael Fortelius and John L. Gittleman and Marcus J. Hamilton and Larisa E. Harding and Kari Lintulaakso and S. Kathleen Lyons and Christy M. McCain and Jordan G. Okie and Juha J. Saarinen and Richard M. Sibly and Patrick R. Stephens and Jessica M. Theodor and Mark D. Uhen},
  pages={1216 - 1219}
How Mammals Grew in Size Mammals diversified greatly after the end-Cretaceous extinction, which eliminated the dominant land animals (dinosaurs). Smith et al. (p. 1216) examined how the maximum size of mammals increased during their radiation in each continent. Overall, mammal size increased rapidly, then leveled off after about 25 million years. This pattern holds true on most of the continents—even though data are sparse for South America—and implies that mammals grew to fill available niches… 

The maximum rate of mammal evolution

An exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous–Paleogene extinction event is found and a basic asymmetry in macroevolution is indicated: very large decreases can happen at more than 10 times the rate of increases.

Ontogenetic niche shifts in dinosaurs influenced size, diversity and extinction in terrestrial vertebrates

A model is developed that quantifies the impact of size-specific interspecies competition on abundances of differently sized dinosaurs and mammals, taking into account the extended niche breadth realized during ontogeny among large oviparous species and predicts low diversity at intermediate size classes, consistent with observed diversity distributions of dinosaurs, and of Mesozoic land vertebrates in general.

The evolution of mammal body sizes: responses to Cenozoic climate change in North American mammals

This model argues that the body sizes of Nearctic mammals were moulded by Cenozoic climate and vegetation changes, and reemphasizes the necessity of considering the evolutionary history and resultant form and function of mammalian morphotypes when attempting to understand contemporary mammalian body size distributions.

diversity and extinction in terrestrial vertebrates Ontogenetic niche shifts in dinosaurs influenced size

Dinosaurs have more complex ontogenetic lifehistories than similar-sized mammals, implying more extensive ecological niche shifts through their develop-ment, and their implications for body size distributions of the dominant terrestrialvertebrate groups of the Mesozoic and Cenozoic.

Patterns of maximum body size evolution in Cenozoic land mammals: eco-evolutionary processes and abiotic forcing

The temporal distribution of maximum size observed within individual orders globally and on separate continents is investigated and it is concluded that the macroevolutionary patterns observed are a result of the interplay between eco-evolutionARY processes and abiotic forcing.

Body size evolution in palaeognath birds is consistent with Neogene cooling-linked gigantism

Patterns of mammalian jaw ecomorphological disparity during the Mesozoic/Cenozoic transition

Total mammal disparity exceeded its Mesozoic maximum for the first time during the Eocene, when therian mammals began exploring previously unoccupied regions of function space, and probably reflects the duration of evolutionary recovery after the K/Pg mass extinction event.

Adaptive radiation of multituberculate mammals before the extinction of dinosaurs

It is shown that in arguably the most evolutionarily successful clade of Mesozoic mammals, the Multituberculata, an adaptive radiation began at least 20 million years before the extinction of non-avian dinosaurs and continued across the Cretaceous–Paleogene boundary.

Changes in the diet and body size of a small herbivorous mammal (hispid cotton rat, Sigmodon hispidus ) following the late Pleistocene megafauna extinction

It is suggested that small mammals may be as sensitive to shifts in local biotic interactions within their ecosystem as they are to changes in climate and large‐scale biodiversity loss.



Dinosaurs, dragons, and dwarfs: The evolution of maximal body size

The body mass of the top species was found to increase with increasing land area, with a slope similar to that of the relation between body mass and home range area, suggesting that maximum body size is determined by the number of home ranges that can fit into a given land area.

The fossil record of North American mammals: evidence for a Paleocene evolutionary radiation.

  • J. Alroy
  • Geography, Environmental Science
    Systematic biology
  • 1999
Paleofaunal data confirm that there were fewer mammalian species during the latest Cretaceous than during any interval of the Cenozoic, and that a massive diversification took place during the early Paleocene, immediately after a mass extinction.

Cope's rule and the dynamics of body mass evolution in North American fossil mammals.

  • J. Alroy
  • Environmental Science
  • 1998
Body mass estimates for 1534 North American fossil mammal species show that new species are on average 9.1% larger than older species in the same genera, which partially explains the unwavering lower size limit and the gradually expanding mid-sized gap.


  • J. Trammer
  • Environmental Science, Biology
    Evolution; international journal of organic evolution
  • 2005
The observed shifts in maximum body size approximate the rate of diversification per unit of time to the power of about 0.5.

Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity

This period-level compilation of the largest known fossil organisms demonstrates that maximum size increased by 16 orders of magnitude since life first appeared in the fossil record.

Evolution of Body Size in the Woodrat over the Past 25,000 Years of Climate Change

Microevolutionary changes in the body size of the bushy-tailed woodrat (Neotoma cinerea) since the last glacial maximum were estimated from measurements of fecal pellets preserved in paleomiddens

Estimating mean body masses of marine mammals from maximum body lengths

Estimates of mean body mass were derived for 106 living species of marine mammals from generalized survival models applied to growth curves published for 17 species of cetaceans and 13 species of pinnipeds.

Transformation and diversification in early mammal evolution

Newly discovered fossils show that evolution of such key characters as the middle ear and the tribosphenic teeth is far more labile among Mesozoic mammals.

The Rise of Oxygen over the Past 205 Million Years and the Evolution of Large Placental Mammals

It is suggested that the overall increase in oxygen, mediated by the formation of passive continental margins along the Atlantic Ocean during the opening phase of the current Wilson cycle, was a critical factor in the evolution, radiation, and subsequent increase in average size of placental mammals.