Nonplantigrade Foot Posture: A Constraint on Dinosaur Body Size.
Nonplantigrade Foot Posture: A Constraint on Dinosaur Body Size.
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DOI：
10.1371/journal.pone.0145716
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Kubo MO
中科院分区：
文献类型：
--
作者：
Kubo T;Kubo MO
恐龙有功能上的数字化或亚蹄类足部姿势。恐龙与它们的直系祖先是中生代唯一的陆地非植物纲动物。现存的陆生哺乳动物的最佳体型因其足部姿势的不同而有所不同(平地级、数字化和蹄状)，然而，尽管恐龙的体型已经得到了深入的研究，但非植物级的足姿与恐龙体型的关系却从未被研究过。根据这项研究中提供的一个大型数据集，除大型哺乳动物(即象鼠)、少数翼龙类恐龙和非恐龙鸟鸟(即恐龙的直系祖先)外，所有非植物纲动物(包括不活动的恐龙、不活动的陆栖鸟类、现存的哺乳动物和灭绝的极地哺乳动物)的身体尺寸都在500克以上。当非植物等级的四足动物从植物等级的祖先进化而来时，具有非植物等级足部姿势的谱系显示出遵循科普规则的身体尺寸稳步增加。相比之下，同时代的植物性血统没有显示出体型演变的趋势，并且在很大程度上被限制在较小的体型上。这种特定于足部姿势的体型进化模式在中生代和新生代都反复发生。尽管受到白垩纪末期物种灭绝的干扰，但从侏罗纪到现在，中到大体型的物种一直以非植食性动物为主；相反，在非进化的陆生四足动物中，体型较小的物种完全由植物性动物组成。
Dinosaurs had functionally digitigrade or sub-unguligrade foot postures. With their immediate ancestors, dinosaurs were the only terrestrial nonplantigrades during the Mesozoic. Extant terrestrial mammals have different optimal body sizes according to their foot posture (plantigrade, digitigrade, and unguligrade), yet the relationship of nonplantigrade foot posture with dinosaur body size has never been investigated, even though the body size of dinosaurs has been studied intensively. According to a large dataset presented in this study, the body sizes of all nonplantigrades (including nonvolant dinosaurs, nonvolant terrestrial birds, extant mammals, and extinct Nearctic mammals) are above 500 g, except for macroscelid mammals (i.e., elephant shrew), a few alvarezsauroid dinosaurs, and nondinosaur ornithodirans (i.e., the immediate ancestors of dinosaurs). When nonplantigrade tetrapods evolved from plantigrade ancestors, lineages with nonplantigrade foot posture exhibited a steady increase in body size following Cope’s rule. In contrast, contemporaneous plantigrade lineages exhibited no trend in body size evolution and were largely constrained to small body sizes. This evolutionary pattern of body size specific to foot posture occurred repeatedly during both the Mesozoic and the Cenozoic eras. Although disturbed by the end-Cretaceous extinction, species of mid to large body size have predominantly been nonplantigrade animals from the Jurassic until the present; conversely, species with small body size have been exclusively composed of plantigrades in the nonvolant terrestrial tetrapod fauna.