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Dinosaurian growth rates and bird origins


Dinosaurs, like other tetrapods, grew more quickly just after hatching than later in life. However, they did not grow like most other non-avian reptiles, which grow slowly and gradually through life. Rather, microscopic analyses of the long-bone tissues show that dinosaurs grew to their adult size relatively quickly, much as large birds and mammals do today. The first birds reduced their adult body size by shortening the phase of rapid growth common to their larger theropod dinosaur relatives. These changes in timing were primarily related not to physiological differences but to differences in growth strategy.

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Figure 1: Cladogram of archosaurian taxa, after various sources, with subadult long-bone growth rates.
Figure 2: Comparative growth histories of the hadrosaurian dinosaur Maiasaura11 and the giant Cretaceous crocodile Deinosuchus, with ‘typical’ crocodiles for comparison15.
Figure 3: Transverse mid-shaft thin-sections of cortical bone of representative theropod taxa, showing the evolution of tissue from basal theropods to crown-group birds.
Figure 4: Cladogram of representative birds and other theropod dinosaurs, using crocodiles as an outgroup, to show the evolution of the growth strategies suggested by histological patterns, sampled in all taxa here except Archaeopteryx.


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We thank M. Zelditch, J. Hutchinson and J. Cubo for comments, and K. Angielczyk for phylogenetic help. E. Lamm prepared the thin-sections. This work was supported by The Charlotte and Walter Kohler Charitable Trust, the CNRS, the Collège de France, the Miller Institute for Basic Research, and the Committee on Research of the University of California, Berkeley. This is University of California Museum of Paleontology Contribution No. 1741.

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Correspondence to Kevin Padian.

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Padian, K., de Ricqlès, A. & Horner, J. Dinosaurian growth rates and bird origins. Nature 412, 405–408 (2001).

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