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Body size distribution of the dinosaurs.

O'Gorman EJ, Hone DW - PLoS ONE (2012)

Bottom Line: Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups.We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations.We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates.

View Article: PubMed Central - PubMed

Affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.

ABSTRACT
The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.

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Frequency distribution of maximum species body size for Cenozoic mammals (in grey) overlaid on the distribution for extant mammals (in white).Curve fitting is based on a combination of kernel density estimation and smoothed bootstrap resampling. The figure clearly highlights the reduced frequency of small-bodied species in the Cenozoic mammal dataset, while the frequency of large-bodied species is comparable between both datasets.
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pone-0051925-g003: Frequency distribution of maximum species body size for Cenozoic mammals (in grey) overlaid on the distribution for extant mammals (in white).Curve fitting is based on a combination of kernel density estimation and smoothed bootstrap resampling. The figure clearly highlights the reduced frequency of small-bodied species in the Cenozoic mammal dataset, while the frequency of large-bodied species is comparable between both datasets.

Mentions: The exploration of other fossilised taxa, the extinct pterosaurs and Cenozoic mammals, revealed that both these groups have positively-skewed distributions of maximum species body size, in contrast to the dinosaurs (Fig. 2g–h and Table 2). The body size distribution for pterosaurs is not significantly different from a normal distribution (Lilliefors test: D = 0.117, p = 0.084; see Table 2). However, the existing dataset for pterosaur species body mass is very limited (n = 50), so these trends should be interpreted with caution. The Cenozoic mammals are characterised by markedly fewer small species compared to extant mammals as evidenced by the truncated peak around a body mass of log10(2) g (see Fig. 2h and Fig. 3). Additionally, the body size distribution of these two groups are significantly different from each other (Kolmogorov-Smirnov test: D = 0.218, p<0.001). This provides evidence of taphonomic bias against the discovery of smaller species in the fossil record and yet the distribution of Cenozoic mammals is still distinctly positively-skewed and significantly different from a normal distribution (Lilliefors test: D = 0.089, p<0.001; see Table 2).


Body size distribution of the dinosaurs.

O'Gorman EJ, Hone DW - PLoS ONE (2012)

Frequency distribution of maximum species body size for Cenozoic mammals (in grey) overlaid on the distribution for extant mammals (in white).Curve fitting is based on a combination of kernel density estimation and smoothed bootstrap resampling. The figure clearly highlights the reduced frequency of small-bodied species in the Cenozoic mammal dataset, while the frequency of large-bodied species is comparable between both datasets.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3526529&req=5

pone-0051925-g003: Frequency distribution of maximum species body size for Cenozoic mammals (in grey) overlaid on the distribution for extant mammals (in white).Curve fitting is based on a combination of kernel density estimation and smoothed bootstrap resampling. The figure clearly highlights the reduced frequency of small-bodied species in the Cenozoic mammal dataset, while the frequency of large-bodied species is comparable between both datasets.
Mentions: The exploration of other fossilised taxa, the extinct pterosaurs and Cenozoic mammals, revealed that both these groups have positively-skewed distributions of maximum species body size, in contrast to the dinosaurs (Fig. 2g–h and Table 2). The body size distribution for pterosaurs is not significantly different from a normal distribution (Lilliefors test: D = 0.117, p = 0.084; see Table 2). However, the existing dataset for pterosaur species body mass is very limited (n = 50), so these trends should be interpreted with caution. The Cenozoic mammals are characterised by markedly fewer small species compared to extant mammals as evidenced by the truncated peak around a body mass of log10(2) g (see Fig. 2h and Fig. 3). Additionally, the body size distribution of these two groups are significantly different from each other (Kolmogorov-Smirnov test: D = 0.218, p<0.001). This provides evidence of taphonomic bias against the discovery of smaller species in the fossil record and yet the distribution of Cenozoic mammals is still distinctly positively-skewed and significantly different from a normal distribution (Lilliefors test: D = 0.089, p<0.001; see Table 2).

Bottom Line: Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups.We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations.We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates.

View Article: PubMed Central - PubMed

Affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.

ABSTRACT
The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.

Show MeSH