Metatherian

Evolutionary history

The earliest possible known metatherian is Sinodelphys szalayi, which lived in China during the Early Cretaceous around 125 million years ago (mya). This makes it a contemporary to some early eutherian species that have been found in the same area. However, Bi et al. (2018) reinterpreted Sinodelphys as an early member of Eutheria. The oldest uncontested metatherians are now 110 million year old fossils from western North America. Metatherians were widespread in Asia and North America during the Late Cretaceous, including both Deltatheroida and Marsupialiformes, with fossils also known from Europe during this time. During the Late Cretaceous, metatherians were more diverse than eutherians in North America. Metatherians underwent a severe decline during the Cretaceous–Paleogene extinction event, more severe than that suffered by contemporary eutherians and multituberculates, and were slower to recover diversity.