據(jù)《每日郵報》1月29日報道,，很多人相信6550萬年前小行星撞地球?qū)е驴铸垳缃^,。但最近加拿大科學家發(fā)現(xiàn)的化石顯示，當時恐龍并未完全滅絕,，它們又多活了70萬年,。
加拿大阿爾伯塔大學的科學家，利用最新的“直接測年法”,，重新測定了在新墨西哥州發(fā)現(xiàn)的食草恐龍鴨嘴龍化石的年代,。結果顯示,，它們的化石骨骼是6480萬年前的,。這就意味著，6650萬年前所謂的恐龍大滅絕后,，有的恐龍至少又存活了70萬年,。
領導此項研究的科學家拉里·希曼說，用激光束對化石骨頭粒子進行直接掃描,，然后對其進行放射性年代測定,，只要確定骨骼化石中鉛同位素的組成含量，就能得出動物死亡的時間,，甚至包括這種生物死前的飲食,。
拉里分析這些恐龍幸存的原因包括，某些地方的植被并未完全遭到毀滅,，鴨嘴龍得以存活。此外,，一些在極端天氣中保存下來的恐龍蛋,，可能也是部分恐龍幸存下來的因素,。此前,，很多專家都認為，6550萬年前,，一顆巨大隕石撞擊所形成的碎片和塵土擋住了陽光，引起極端的氣候變化,，隨后導致全球大量植物的枯亡,，也因此造成恐龍滅絕。（生物谷Bioon.com）
生物谷推薦原文出處：
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.
