Nail-tail wallabies are named for the claw-like spur at the end of their tail, a spur whose purpose no-one really knows. Only one nail-tail wallaby has any significant range in today's world, the northern or sandy nail-tail wallaby Onychogalea unguifera. This species lives in areas with soft clay or sandy loam soil, and typically shrubland, coastal plain with scattered thickets, or open tussocky woodland, across much of northern Australia. It emits a grunt with each hop. The other species were somewhat smaller, and have been driven to extinction or near-extinction by introduced foxes.