《Nature》：世界上最大、最古老的暴龙

生物谷

本期封面刊登的是世界上最大、我们现在知道也是最古老的暴龙（Tyrannosaurus rex）（Field Museum FMNH PR2081）的骨架照片。这是一个衰老的成年个体，其最大生长速度为每天2.1公斤。生长在其20岁左右停止，死亡发生在29岁左右。对暴龙及其三个最近亲缘种的生长速度所做的直接测量结果，被用来生成这些动物的年龄/质量生长曲线。暴龙发育变化的时间与其祖先的类似，说明加快的生长速度是暴龙体形庞大的关键。封面背景是该动物径骨显微结构的一个偏振显微照片，照片上显示了可被用来指示年龄的生长线。

Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs

GREGORY M. ERICKSON^1,2, PETER J. MAKOVICKY³, PHILIP J. CURRIE⁴, MARK A. NORELL², SCOTT A. YERBY⁵ & CHRISTOPHER A. BROCHU⁶

¹ Department of Biological Science, Florida State University, Tallahassee, Florida 32306-1100, USA
² Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024-5192, USA
³ Department of Geology, The Field Museum, 1400 S. Lake Shore Drive, Chicago, Illinois 60605, USA
⁴ Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta T0J 0Y0, Canada
⁵ Department of Biomechanical Engineering, Stanford University, Stanford, California 94305, USA
⁶ Department of Geoscience, University of Iowa, Iowa City, Iowa 52242, USA

Correspondence and requests for materials should be addressed to G.M.E. (gerickson@bio.fsu.edu).

How evolutionary changes in body size are brought about by variance in developmental timing and/or growth rates (also known as heterochrony) is a topic of considerable interest in evolutionary biology. In particular, extreme size change leading to gigantism occurred within the dinosaurs on multiple occasions. Whether this change was brought about by accelerated growth, delayed maturity or a combination of both processes is unknown. A better understanding of relationships between non-avian dinosaur groups and the newfound capacity to reconstruct their growth curves make it possible to address these questions quantitatively. Here we study growth patterns within the Tyrannosauridae, the best known group of large carnivorous dinosaurs, and determine the developmental means by which Tyrannosaurus rex, weighing 5,000 kg and more, grew to be one of the most enormous terrestrial carnivorous animals ever. T. rex had a maximal growth rate of 2.1 kg d^-1, reached skeletal maturity in two decades and lived for up to 28 years. T. rex's great stature was primarily attained by accelerating growth rates beyond that of its closest relatives.

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