画家绘制的鹦鹉龙图画,好像一只巨大的鹦鹉。鹦鹉龙有结实有力的上下腭,爱吃坚果,但是比鹦鹉在地球上生存时代要早6000万年
鹦鹉龙的头骨和现代鹦鹉头骨的对照图,从中我们可以发现其中的相似性
科研人员表示,他们发现一种距今1.1亿年前的一种恐龙长有像鹦鹉一样的喙,能够咬开坚果,就像一只吃坚果的巨大鹦鹉。
科研人员把这种恐龙称为鹦鹉龙,属于角龙的一种。角龙恐龙是一种鸟臀类草食性恐龙,活跃于白垩纪后期。明显的特征包括脸上的角及勾状的喙与头後方骨质的的皱摺。这具鹦鹉龙化石2001年发现于我国内蒙古地区的戈壁沙漠里。最近古生物学家对这具恐龙化石进行了研究,发现头骨的一些特征表明这种恐龙以坚果和种子为食。
芝加哥大学的古生物学家保罗-瑟雷诺说,“这具恐龙化石头骨和鹦鹉头骨的相似性非常接近,鹦鹉是恐龙进化发展的后代,而鹦鹉以喜欢吃坚果而出名。”保罗-瑟雷诺和两名中国同事把他们的研究成果发表在《皇家学会会报B辑:生物科学》(Proceedings of the Royal Society,Series B: Biological Sciences)上,对这只恐龙进行了详细的描述。
科研人员还找到了另外的有力证据证明这只恐龙喜欢吃坚果。瑟雷诺说,“这只恐龙胃里有超过50块的小石头,能够研磨它所吃下的任何食物,而这是和它3英尺的体长不成比例的。”相似地,鸟类砂囊里的石块数量和大小和鸟类的食物爱好是相关联的。砂囊里的石块更多、更大表明鸟类吃的食物更坚硬,比如坚果和种子。
瑟雷诺认为这只恐龙以一种特殊的方式进食,称之为“倾斜角度”咀嚼。“鹦鹉龙的两腭向后、向上张开,而不仅仅是前后张合。”瑟雷诺说,“其他草食性恐龙和派性动物是不是采用同样的咀嚼原理,还需要进一步研究。”
研究出恐龙吃的是什么是一件艰巨的工作,不过科学家至少两次发现了恐龙体内的食物残存。比如科学家发现了一只昵称为“莱昂纳多”的恐龙胃部的食物残存,表明它最后吃下了充分咀嚼过的树叶。(生物谷Bioon.com)
生物谷推荐原始出处:
Proc. R. Soc. B June 17, 2009, doi: 10.1098/rspb.2009.0691
A new psittacosaur from Inner Mongolia and the parrot-like structure and function of the psittacosaur skull
Paul C. Sereno1,*, Zhao Xijin2 and Tan Lin3
1Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA
2Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, People's Republic of China
3Long Hao Institute of Geology and Paleontology, Bureau of Land and Resources, 010010 Hohhot, People's Republic of China
We describe a new species of psittacosaur, Psittacosaurus gobiensis, from the Lower Cretaceous of Inner Mongolia and outline a hypothesis of chewing function in psittacosaurs that in many respects parallels that in psittaciform birds. Cranial features that accommodate increased bite force in psittacosaurs include an akinetic skull (both cranium and lower jaws) and differentiation of adductor muscle attachments comparable to that in psittaciform birds. These and other features, along with the presence of numerous large gastroliths, suggest that psittacosaurs may have had a high-fibre, nucivorous (nut-eating) diet.
Psittacosaurs, alone among ornithischians, generate oblique wear facets from tooth-to-tooth occlusion without kinesis in either the upper or lower jaws. This is accomplished with a novel isognathous jaw mechanism that combines aspects of arcilineal (vertical) and propalinal (horizontal) jaw movement. Here termed clinolineal (inclined) jaw movement, the mechanism uses posteriorly divergent tooth rows, rather than kinesis, to gain the added width for oblique occlusion. As the lower tooth rows are drawn posterodorsally into occlusion, the increasing width between the upper tooth rows accommodates oblique shear. With this jaw mechanism, psittacosaurs were able to maintain oblique shearing occlusion in an akinetic skull designed to resist high bite forces.