Original: The Virginia Opossum (Didelphis virginiana), commonly known as the North American Opossum or Tlacuache in Mexico, is the only marsupial found in North America north of Mexico.
Simplified: The Virginia Opossum (Didelphis virginiana), sometimes called a possum, is a marsupial. There are lots of marsupials in Australia, but the Virginia Opossum is the only North American marsupial.