Department of Ecology, Zoological Institute, University of Mainz, Mainz, Germany.
PLoS One. 2013 Oct 30;8(10):e74317. doi: 10.1371/journal.pone.0074317. eCollection 2013.
To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today's crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal's core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited by overheating impossible.
为了估算体温（BT），Gillooly、Alleen 和 Charnov（2006）使用了一个方程，该方程根据体重和最大生长率（MGR）预测 BT，后者保存在个体发育生长轨迹中（BT 方程）。这些作者的研究结果表明恐龙类具有惯性恒温性，并表明由于过热，恐龙类的最大体型最终受到 BT 的限制。在本文中，我重新审视了 Gillooly、Alleen 和 Charnov（2006）的这一假设。我首先研究了从今天的鳄鱼、鸟类和哺乳动物的 BT 方程得出的 BT 是否与动物的核心温度一致。其次，我应用 BT 方程估算了比 Gillooly、Alleen 和 Charnov（2006）更多的恐龙。特别是，我估计了始祖鸟（来自两个 MGR）、鸟脚类恐龙（两个）、兽脚类恐龙（三个）、原蜥脚类恐龙（三个）和蜥脚类恐龙（九个）的 BT。对于现生物种，从 BT 方程估计的 BT 值是对动物核心温度的粗略估计。对于鸟类，BT 总是被严重高估，而对于鳄鱼，BT 被低估；对于哺乳动物，BT 的准确性适中。我认为，BT 方程中使用的 MGR（回归线的截距和指数，对数-对数转换）和 Arrhenius 模型的参数化的分类群特异性差异以及物种的生态和进化适应都会导致这些不准确。无论从 BT 方程估计的 BT 值的发现的不准确性如何，并且与 Gillooly、Alleen 和 Charnov（2006）的结果相反，我没有发现所有研究的恐龙（蜥脚形亚目，蜥脚类）的 BT 随体重增加而增加。这一观察结果质疑了由于过热，恐龙类的最大体型最终受到 BT 的限制。然而，从 BT 方程得出的恐龙 BT 值的普遍高度不准确，使得对恐龙的体型是否最终受到过热的限制进行可靠测试变得不可能。
