图片说明:新研究确证了恐龙与鸟类、乳齿象与现代大象的亲缘关系。
(图片来源:Zina Deretsky, National Science Foundation)
美国科学家近日在分子水平上分析了6800万年前的暴龙(Tyrannosaurus rex)的蛋白质片断,并与21种现代物种的蛋白质序列进行了比较,结果确证,恐龙与鸟类具有共同祖先。研究文章发表在4月25日的《科学》(Science)杂志上。
领导此次研究的是美国哈佛医学院的John M. Asara。研究所用的胶原蛋白(collagen protein)取自2003年发现的一段暴龙腿骨化石,Asara和同事曾于去年对这段蛋白质进行了测序。
在最新的研究中,Asara和同事将这段蛋白质与其它21种物种的相关蛋白质进行了比较,目的在于利用分子证据将暴龙置于动物界进化树的适当位置。
Asara说:“我们确定了,与其它我们研究的物种相比,包括美洲鳄和绿变色龙等现代爬行动物,暴龙与鸟类(鸵鸟和鸡)具有更近的亲缘关系。
科学家之前一直怀疑鸟类是恐龙现存最近的亲属,这一假设很大程度上依赖于鸟类和恐龙骨骼形态上的相似性。此次研究则是从分子水平上确证了二者之间的亲缘关系。另外,此次研究还同时得出结论认为,16万至60万年前的乳齿象(mastodon)与现代大象之间存在紧密的系统发生联系。(科学网 梅进/编译)
生物谷推荐原始出处:
(Science),Vol. 320. no. 5875, p. 499,Chris L. Organ,John M. Asara
Molecular Phylogenetics of Mastodon and Tyrannosaurus rex
Chris L. Organ,1,2 Mary H. Schweitzer,3,4 Wenxia Zheng,3 Lisa M. Freimark,5 Lewis C. Cantley,5,6 John M. Asara5,6*
We report a molecular phylogeny for a nonavian dinosaur, extending our knowledge of trait evolution within nonavian dinosaurs into the macromolecular level of biological organization. Fragments of collagen 1(I) and 2(I) proteins extracted from fossil bones of Tyrannosaurus rex and Mammut americanum (mastodon) were analyzed with a variety of phylogenetic methods. Despite missing sequence data, the mastodon groups with elephant and the T. rex groups with birds, consistent with predictions based on genetic and morphological data for mastodon and on morphological data for T. rex. Our findings suggest that molecular data from long-extinct organisms may have the potential for resolving relationships at critical areas in the vertebrate evolutionary tree that have, so far, been phylogenetically intractable.
1 Harvard University, Cambridge, MA 02138, USA.
2 Museum of Comparative Zoology, Cambridge, MA 02138, USA.
3 North Carolina State University, Raleigh, NC 27695, USA.
4 North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA.
5 Beth Israel Deaconess Medical Center, Boston, MA 02115, USA.
6 Harvard Medical School, Boston, MA 02115, USA.