Biology of the sauropod dinosaurs: the evolution of gigantism.
Bottom Line: Scaling relationships between gastrointestinal tract size and basal metabolic rate (BMR) suggest that sauropods compensated for the lack of particle reduction with long retention times, even at high uptake rates.The extensive pneumatization of the axial skeleton resulted from the evolution of an avian-style respiratory system, presumably at the base of Saurischia.An avian-style respiratory system would also have lowered the cost of breathing, reduced specific gravity, and may have been important in removing excess body heat.
Affiliation: Steinmann Institute, University of Bonn, Germany. email@example.comShow MeSH
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Mentions: All else being equal, would an increased level of atmospheric oxygen allow the evolution of gigantic terrestrial tetrapods? This possibility is suggested by the example discussed above of the uniquely gigantic dragonflies of the Carboniferous (Lighton, 2007). Hengst et al. (1996) explored this hypothesis for sauropod dinosaurs, based on the premise of an oxygen level of 30% or above in the Jurassic atmosphere (Landis et al., 1996). Physically modelling respiration in the Late Jurassic sauropod Apatosaurus, they concluded that the respiratory system of this animal could not have delivered enough oxygen to the tissues at today's oxygen levels. This applied even under the assumption that Apatosaurus had the basal metabolic rate of a reptilian ectotherm. However, the hypothesis of Hengst et al. (1996) is superseded by the likely presence of a bird-like lung in sauropods and the current understanding that oxygen levels were significantly lower in the Jurassic and Cretaceous than today (Gans et al., 1999; Dudley, 1998; Berner, 2006; Berner et al., 2007; see also Fig. 8) or at about the same level (Bergman, Lenton & Watson, 2004; Belcher & McElwain, 2008).
Affiliation: Steinmann Institute, University of Bonn, Germany. firstname.lastname@example.org