Simplify the following text for a Grade 11 native English-speaking person.
Original: The koala ( Phascolarctos cinereus ) is an arboreal herbivorous marsupial native to Australia , and the only extant representative of the family Phascolarctidae .
Simplified: Koalas ( Phascolarctos cinereus ) are herbivore marsupials that live in eastern Australia . They are the only species of the family Phascolarctidae .