Simplify the following text for a Grade 12 native English-speaking person.
Original: The Red-necked Wallaby ( Macropus rufogriseus ) is a medium-sized marsupial macropod , common in the more temperate and fertile parts of eastern Australia , including Tasmania .
Simplified: The Red-necked Wallaby ( Macropus rufogriseus ) is a medium-sized macropod , common in parts of eastern Australia .