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

小行星9527811 自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和他们的同事们继续着对恐龙、鸟类和哺乳动物的研究。化石收集最近恢复与蒙古和中国的合作者，这些新的探险正在产生丰富的标本，既有已知的，也有全新的恐龙和早期的类恐龙哺乳动物。材料包括精美保存的头骨和多瘤动物的骨骼，以及被认为属于胎盘哺乳动物基底类群的分类群。对这些材料的研究将为早期类哺乳动物爬行动物和真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。来自齿系、头骨和颅后骨骼的新特征将使用传统的古生物学技术以及新的CT（计算机辅助断层扫描）扫描标本，避免破坏性采样。 AMNH科学家与路易斯维尔大学和国外的同事合作，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相结合，并将其结果与活分类群的分子（DNA）研究数据进行比较。特别是，有据可查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应该为哺乳动物及其近亲的早期谱系的进化历史提供可靠的估计。

9527811 Novacek 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.