Koonchera Dune is a prominent sand ridge fringed by a complex of ephemeral swamps and open plains on the edge of Sturt Stony Desert, northeastern South Australia. In 1931 mammalogist Hedley Herbert Finlayson rediscovered the desert rat-kangaroo or ngudlukanta (<i>Caloprymnus campestris</i>) here, and also captured lesser bilby or yallara (<i>Macrotis leucura</i>), bilby (<i>Macrotis lagotis</i>), and plains mouse (<i>Pseudomys australis</i>). This was the last time any of these mammals were recorded at Koonchera; ngudlukanta and yallara are globally extinct, the bilby is extinct on mainland South Australia, and the plains mouse is listed as vulnerable throughout its diminishing range. Prior to these and other recent extinctions totalling a minimum six species, we estimate that Koonchera supported at least 24 native mammals. In 2018 and 2019 we surveyed mammals here, detecting 11 native mammals including three rare or threatened species: fawn hopping mouse (<i>Notomys cervinus</i>), dusky hopping mouse (<i>N. fuscus</i>), and long-haired rat (<i>Rattus villosissimus</i>). We also detected seven introduced species, including feral cat (<i>Felis catus</i>), fox (<i>Vulpes vulpes</i>), European rabbit (<i>Oryctolagus cuniculus</i>), and feral pig (<i>Sus scrofa</i>). Physically, Koonchera and the Lake Eyre Basin region is much the same as Finlayson would have found it in 1931, but our work shows a proliferation of feral and introduced species and a decline of native mammals, especially medium-sized Critical Weight Range (CWR) species. If Koonchera and the surrounding landscape is to hold on to its remaining native mammal diversity, coordinated management of threats, principal of which is predation by cats and foxes, and impacts on vegetation and soil from a host of introduced herbivores, is required.