Collaborative Research: Cretaceous Mammals From Mongolia and Mammalian Higher-Level Phylogeny

自从20世纪20年代到蒙古戈壁沙漠进行著名的化石采集探险以来，美国自然历史博物馆的科学家们和他们的同事们一直保持着研究白垩纪恐龙、鸟类和哺乳动物的杰出传统。最近，蒙古和中国的合作者重新开始收集化石，这些新的探险活动获得了大量已知的和全新的恐龙和早期类恐龙哺乳动物群体（分类群）的标本。材料包括被认为属于胎盘哺乳动物基群的多瘤动物和分类群的保存完好的头骨和骨骼。对这些材料的研究将为早期类哺乳动物爬行动物和真正哺乳动物早期谱系的分类多样性和系统发育（进化）关系提供新的证据。利用传统的古生物学技术以及新的CT（计算机辅助断层扫描）对标本进行扫描，可以避免破坏性采样，从而收集来自牙列、头骨和颅后骨骼的新特征。AMNH的科学家们与路易斯维尔大学和国外的同事们合作，正在努力将这些早期化石哺乳动物的分类群和特征的新知识与已知化石和现存群体的知识结合起来，然后将他们的结果与现存分类群的分子（DNA）研究数据进行比较。特别是，充分记录的化石物种将为分子进化速率的理论研究提供校准点。形态学和分子证据的最终整合将为哺乳动物及其近亲的早期谱系提供可靠的进化史估计。

9625431 Wible Since the famous fossil-collecting expeditions to the Gobi Desert of Mongolia in the 1920s, scientists at the American Museum of Natural History and their colleagues have continued an outstanding tradition of research on Cretaceous-age dinosaurs, birds, and mammals. Fossil collections resumed recently with Mongolian and Chinese collaborators, and these new expeditions are yielding abundant specimens of both known and entirely new groups (taxa) of dinosaurs and early dinosaur-like mammals. Material includes exquisitely preserved skulls and skeletons of multituberculates and taxa considered to belong to basal groups of placental mammals. Study of this material will provide new evidence bearing on taxonomic diversity and phylogenetic (evolutionary) relationships of early mammal-like reptiles and of the early lineages of true mammals. New characters from dentition, skull, and postcranial skeletons will be amassed using traditional paleontological techniques as well as new CT (computer-aided tomography) scanning of specimens, which avoids destructive sampling. AMNH scientists in association with colleagues at University of Louisville and abroad are working to integrate the new knowledge of taxa and of characters from these early fossil mammals with knowledge from known fossil and extant groups, and in turn to compare their results with data from molecular (DNA) studies of living taxa. In particular, well-documented fossil species will provide calibration points for theoretical studies of molecular evolutionary rates. And the eventual integration of morphological and molecular evidence should provide robust estimates of evolutionary history for the early lineages of mammals and their close relatives.