本期封面刊登的是世界上最大,、我們現(xiàn)在知道也是最古老的暴龍（Tyrannosaurus rex）（Field Museum FMNH PR2081）的骨架照片,。這是一個(gè)衰老的成年個(gè)體,，其最大生長(zhǎng)速度為每天2.1公斤。生長(zhǎng)在其20歲左右停止,，死亡發(fā)生在29歲左右,。對(duì)暴龍及其三個(gè)最近親緣種的生長(zhǎng)速度所做的直接測(cè)量結(jié)果，被用來(lái)生成這些動(dòng)物的年齡/質(zhì)量生長(zhǎng)曲線,。暴龍發(fā)育變化的時(shí)間與其祖先的類似,，說明加快的生長(zhǎng)速度是暴龍?bào)w形龐大的關(guān)鍵。封面背景是該動(dòng)物徑骨顯微結(jié)構(gòu)的一個(gè)偏振顯微照片,，照片上顯示了可被用來(lái)指示年齡的生長(zhǎng)線,。
Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs
GREGORY M. ERICKSON1,2, 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. ([email protected]).
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.
