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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Small body size and extreme cortical bone remodeling indicate phyletic dwarfism in Magyarosaurus dacus (Sauropoda: Titanosauria)
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Small body size and extreme cortical bone remodeling indicate phyletic dwarfism in Magyarosaurus dacus (Sauropoda: Titanosauria)

机译:小体型和极端的皮质骨重塑表明Magyarosaurus dacus(Sauropoda:Titanosauria)的系统侏儒症

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摘要

Sauropods were the largest terrestrial tetrapods (>10~5 kg) in Earth's history and grew at rates that rival those of extant mammals. Magyarosaurus dacus, a titanosaurian sauropod from the Upper Cretaceous (Maastrichtian) of Romania, is known exclusively from small individuals (<10~3 kg) and conflicts with the idea that all sauropods were massive. The diminutive M. dacus was a classical example of island dwarfism (phyletic nanism) in dinosaurs, but a recent study suggested that the small Romanian titanosaurs actually represent juveniles of a larger-bodied taxon. Here we present strong histolog-ical evidence that M. dacus was indeed a dwarf (phyletic nanoid). Bone histological analysis of an ontogenetic series of Magyarosaurus limb bones indicates that even the smallest Magyarosaurus specimens exhibit a bone microstructure identical to fully mature or old individuals of other sauropod taxa. Comparison of histologies with large-bodied sauropods suggests that Magyarosaurus had an extremely reduced growth rate, but had retained high basal metabolic rates typical for sauropods. The uniquely decreased growth rate and diminutive body size in Magyarosaurus were adaptations to life on a Cretaceous island and show that sauropod dinosaurs were not exempt from general ecological principles limiting body size.
机译:蜥脚类动物是地球历史上最大的陆生四足动物(> 10〜5公斤),其生长速度可与现存哺乳动物相媲美。 Magyarosaurus dacus,一种来自罗马尼亚上白垩纪(马斯特里赫特)的巨人龙类蜥脚类动物,仅以小个体(<10〜3公斤)而闻名,并且与所有蜥脚类动物都是大型的想法相矛盾。矮小的达克斯支原体是恐龙中岛矮化(系统进化论)的一个典型例子,但是最近的一项研究表明,罗马尼亚的小恐龙实际上代表了大体分类群的幼体。在这里,我们提供了有力的组织学证据,证明达克斯分支杆菌确实是一个矮人(系统纳诺德)。对一系列甲齿龙肢体骨的骨组织学分析表明,即使最小的甲齿龙标本也显示出与其他蜥脚类群完全成熟或年老的个体相同的骨微结构。与大型蜥脚类动物的组织学比较表明,Magyarosaurus的生长速度极低,但保留了蜥脚类动物典型的高基础代谢率。玛格罗龙的生长速度下降和体型减小是对白垩纪岛屿生活的适应,表明蜥脚类恐龙并不受豁免限制体型的一般生态学原理的约束。

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