Simplify the following text for a Grade 8 native English-speaking person.
Original: A possum ( plural form : possums ) is any of about 69 small to medium-sized arboreal marsupial species native to Australia , New Guinea , and Sulawesi ( and introduced to New Zealand and China ) .
Simplified: The possum is an Australasian marsupial which was later introduced to China and New Zealand . There are about 69 species alive today .