Metatheria ago, followed by the evolution of deltatheroidian-like taxa in Asia and North America about 120-100 million years ago and then the Paleocene diversification of relatives to the crown marsupials in South America. This makes it a contemporary to some early eutherian species that have been found in the same area. The oldest metatherian fossils are found in present-day China. About 100 mya, the supercontinent Pangaea was in the process of splitting into the northern continent Laurasia and the southern continent Gondwana, with what would become China and Australia already separated by the Tethys Ocean. From there, metatherians spread westward into
Pangean megamonsoon solar insolation shifted toward the Southern Hemisphere. Air then traveled from Laurasia (region of high pressure), across the Tethys Ocean to Gondwana (region of low pressure). Moisture advection toward the Southern Hemisphere would have fueled heavy precipitation along the Gondwana coasts, while Laurasia remained very dry. There are marked similarities between factors contributing to the East Asian monsoon and those that would have influenced Pangean climate. This not only supports the theory that Pangean climate was dominated by the monsoon, but also aids in the study of it, providing paleoclimatologists with a present-day example to which they can compare their