科学家在认真研究鸟类的运动和呼吸方式后，声称这些长着羽毛的人类朋友并非起源于恐龙。
数十年来，人们清楚鸟类的腿骨结构使它们更适合用膝盖奔跑。但是俄勒冈州立大学的研究人员发现，鸟类的腿骨结构还阻止了它们的肺部伸缩，从而使其更适于飞行。包括人类、大象、蜥蜴和暴龙等兽脚亚目恐龙(theropod dinosaurs)在内的，在陆地上行走的任何一种其他动物，都拥有可以移动的腿骨。
这一发现或许将迫使古生物学家重新思考长期以来一直存在的想法：现代鸟类是远古肉食性恐龙的直系后裔。美国研究员约翰·鲁本教授说：“我们竟然不了解最基本的鸟类生物学问题，这令我们非常吃惊。伶盗龙(Velociraptor)不仅在身体的某些部位长有羽毛，而且还喜欢在日落后活动。鸟类可能是从另一种生物进化而来的，在大部分恐龙依然存在的时候，鸟类的进化过程已经开始了。”羽毛、翅膀和鸟类独特的运动方式都是独立进化而来的。
在1.45亿年到6500万年间的白垩纪时代，恐龙和鸟类双双繁盛发展。一直被认为是最古老的鸟类——始祖鸟生活在1.5亿年前，而恐龙先于它，早在2亿年前就已经出现了。鲁本说：“现在似乎已经很清楚，鸟类是单独进化而来的，并不是兽脚亚目恐龙的后裔。”他们的研究结果发表在《形态学》杂志上。（生物谷Bioon.com）
生物谷推荐原始出处：
Journal of Morphology DOI:10.1002/jmor.10752
Cardio-pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs
Devon E. Quick *, John A. Ruben
Department of Zoology, Oregon State University, Corvallis, Oregon 97331
ABSTRACT
Although crocodilian lung and cardiovascular organs are markedly less specialized than the avian heart and lung air-sac system, all living archosaurs possess four-chambered hearts and heterogeneously vascularized, faveolar lungs. In birds, normal lung function requires extensive, dorsally situated nonvascularized abdominal air-sacs ventilated by an expansive sternum and specially hinged costal ribs. The thin walled and voluminous abdominal air-sacs are supported laterally and caudally to prevent inward (paradoxical) collapse during generation of negative (inhalatory) pressure: the synsacrum, posteriorly directed, laterally open pubes and specialized femoral-thigh complex provide requisite support and largely prevent inhalatory collapse. In comparison, theropod dinosaurs probably lacked similarly enlarged abdominal air-sacs, and skeleto-muscular modifications consistent with their ventilation. In the absence of enlarged, functional abdominal air-sacs, theropods were unlikely to have possessed a specialized bird-like, air-sac lung. The likely absence of bird-like pulmonary function in theropods is inconsistent with suggestions of cardiovascular anatomy more sophisticated than that of modern crocodilians.
