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.
