http://phys.org/news/2016-12-mammals-age-dinosaurs-powerful.html

From Greg Wilson and colleagues

A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials. Gregory P. Wilson, Eric G. Ekdale, John W. Hoganson, Jonathan J. Calede & Abby Vander Linden. Nature Communications. DOI: 10.1038/ncomms13734
-Jacqueline