There are two extinct species of Onychogalea:
* The Toolache Wallaby (Onychogalea lunata): This species went extinct in the early 20th century, likely due to habitat loss and predation by introduced predators.
* The Black-Footed Wallaby (Onychogalea frenata): This species likely went extinct in the late 19th century, though there are no confirmed sightings since the early 1800s.
It's important to remember that while the Nailtail Wallaby is still around, it faces a very high risk of extinction, and ongoing conservation efforts are crucial to its survival.