据《每日邮报》1月29日报道，很多人相信6550万年前小行星撞地球导致恐龙灭绝。但最近加拿大科学家发现的化石显示，当时恐龙并未完全灭绝，它们又多活了70万年。
加拿大阿尔伯塔大学的科学家，利用最新的“直接测年法”，重新测定了在新墨西哥州发现的食草恐龙鸭嘴龙化石的年代。结果显示，它们的化石骨骼是6480万年前的。这就意味着，6650万年前所谓的恐龙大灭绝后，有的恐龙至少又存活了70万年。
领导此项研究的科学家拉里·希曼说，用激光束对化石骨头粒子进行直接扫描，然后对其进行放射性年代测定，只要确定骨骼化石中铅同位素的组成含量，就能得出动物死亡的时间，甚至包括这种生物死前的饮食。
拉里分析这些恐龙幸存的原因包括，某些地方的植被并未完全遭到毁灭，鸭嘴龙得以存活。此外，一些在极端天气中保存下来的恐龙蛋，可能也是部分恐龙幸存下来的因素。此前，很多专家都认为，6550万年前，一颗巨大陨石撞击所形成的碎片和尘土挡住了阳光，引起极端的气候变化，随后导致全球大量植物的枯亡，也因此造成恐龙灭绝。（生物谷Bioon.com）
生物谷推荐原文出处：
Geology, 2011; 39 (2): 159 DOI: 10.1130/G31466.1
Direct U-Pb dating of Cretaceous and Paleocene dinosaur bones, San Juan Basin, New Mexico
James E. Fassett1, Larry M. Heaman2 and Antonio Simonetti3
1 552 Los Nidos Drive, Santa Fe, New Mexico 87501, USA
2 Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
3 Department of Civil Engineering and Geological Sciences, Cushing Hall, Notre Dame University, Notre Dame, Indiana 46556, USA
Vertebrate fossils have been important for relative dating of terrestrial rocks for decades, but direct dating of these fossils has heretofore been unsuccessful. In this study we employ recent advances in laser ablation in situ U-Pb dating techniques to directly date two dinosaur fossils from the San Juan Basin of northwestern New Mexico and southwestern Colorado, United States. A Cretaceous dinosaur bone collected from just below the Cretaceous-Paleogene interface yielded a U-Pb date of 73.6 ± 0.9 Ma, in excellent agreement with a previously determined 40Ar/39Ar date of 73.04 ± 0.25 Ma for an ash bed near this site. The second dinosaur bone sample from Paleocene strata just above the Cretaceous-Paleogene interface yielded a Paleocene U-Pb date of 64.8 ± 0.9 Ma, consistent with palynologic, paleomagnetic, and fossil-mammal biochronologic data. This first successful direct dating of fossil vertebrate bone provides a new methodology with the potential to directly obtain accurate dates for any vertebrate fossil.
