美国考古学家日前在科罗拉多州发现了一种小型恐龙种类的化石——果齿龙。这种新发现的恐龙的大小和松鼠差不多。
研究证实，果齿龙身长约为70厘米，最大的也不过体重0.9千克。这种恐龙或许是目前已知的北美洲最小的恐龙了。
世界上还有一种恐龙比果齿龙小，那是在中国发现的“鸟臀目”恐龙，这种恐龙和其他类型的恐龙生活在1.5亿年前，具有部分鸟类特征。但果齿龙除了个头以外，和鸟类祖先始祖鸟没有什么联系。
路易斯·恰佩所在的国际考古专家小组将这一新发现刊登在最新一期的《皇家学会学报》上。恐龙的名字是根据化石发现地命名的。恰佩的研究报告称，果齿龙的牙齿外形表明，它是一种杂食动物，可能既吃植物为食，也吃诸如昆虫等小型动物。
路易斯·恰佩说：“科罗拉多州是发现果齿龙的地方，但可能在北美洲各地都能找到这种恐龙的化石。它们可能和其他大型的恐龙，比如梁龙和腕龙生活在一起。”
据悉，果齿龙的近亲曾经在英国、南非和其他一些国家发现，因为当时大陆还都连接在一起。考古学家声称，果齿龙的发现解释了食草恐龙向杂食恐龙的转化过程。因为环境竞争压力，一部分食草恐龙变得更小，种类也更加多样化。（生物谷Bioon.com）
生物谷推荐原始出处：
Proc. R. Soc. B October 21, 2009, doi: 10.1098/rspb.2009.1494
Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America
Richard J. Butler1,2,*, Peter M. Galton3,?, Laura B. Porro4, Luis M. Chiappe5, Donald M. Henderson6 and Gregory M. Erickson7
1Bayerische Staatssammlung für Pal?ontologie und Geologie, Richard-Wagner-Stra?e 10, 80333 Munich, Germany
2Department of Palaeontology, The Natural History Museum, London SW7 5BD, UK
3Professor Emeritus, College of Naturopathic Medicine, University of Bridgeport, Bridgeport, CT 06604, USA
4Department of Organismal Biology and Anatomy, University of Chicago, IL 60637, USA
5The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA 90007, USA
6Royal Tyrrell Museum of Palaeontology, PO Box 7500, Drumheller, Alberta T0J 0Y0, Canada
7Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA
The extremes of dinosaur body size have long fascinated scientists. The smallest (<1 m length) known dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade.
