Marsupial metatherian is "Sinodelphys szalayi", which lived in China around 125 mya. This makes it a contemporary to some early eutherian species which have been found in the same area. While placental fossils dominate in Asia, marsupial fossils occur in larger numbers in North America. 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 modern North America (still attached to
Saltoposuchus in newly found ecological niches, Pangaea started splitting into Laurasia and Gondwana, and the air was very arid with hot summers and cold winters. After marine life had been wiped out by the mass extinction event, the Triassic waters were populated with very few families of fish. The Triassic Period showed the first development of modern stony corals and a time of modest reef building activity in the shallower waters of the Tethys near the coasts of Pangaea. During the Mesozoic Era, early mammals, reptilian species, and other insects populated the land. Insects that had survived the mass extinction and