The gastric-brooding frogs or platypus frogs (Rheobatrachus) is a genus of extinct ground-dwelling frogs native to Queensland in eastern Australia. The genus consisted of only two species, both of which became extinct in the mid-1980s. The genus is unique because it contains the only two known frog species that incubated the prejuvenile stages of their offspring in the stomach of the mother. The combined ranges of the gastric-brooding frogs comprised less than . Both species were associated with creek systems in rainforests at elevations of between . The causes of the gastric-brooding frogs' extinction are not clearly understood, but habitat loss and degradation, pollution, and some diseases may have contributed. The assignment of the genus to a taxonomic family is hotly debated. Some biologists class them within Myobatrachidae under the subfamily Rheobatrachinae, but others place them in their own family, Rheobatrachidae. Molecular genetics finds it sister to Mixophyes. Scientists at the University of Newcastle and University of New South Wales announced in March 2013 that the frog would be the subject of a cloning attempt, referred to as the ”Lazarus Project", to resurrect the species. Embryos were successfully cloned, and the project eventually hopes to produce a living frog. The southern gastric brooding frog has been listed as Extinct by the IUCN because it has not been recorded in the wild since 1981, and extensive searches over the last 35 years have failed to locate this species. Taxonomy The genus Rheobatrachus was first described in 1973 by David Liem and since has not undergone any scientific classification changes; however its placement has been controversial. It has been placed in a distinct subfamily of Myobatrachidae, Rheobatrachinae; in a separate family, Rheobatrachidae; placed as the sister taxon of Limnodynastinae; and synonymized with Limnodynastinae. In 2006, D. R. Frost and colleagues found Rheobatrachus, on the basis of molecular evidence, to be the sister taxon of Mixophyes and placed it within Myobatrachidae. Both species of gastric-brooding frogs were very different in appearance and behaviour from other Australian frog species. Their large protruding eyes and short, blunt snout along with complete webbing and slimy bodies differentiated them from all other Australian frogs. The largely aquatic behaviour exhibited by both species was only shared (in Australia) with the Dahl's aquatic frog and their ability to raise their young in the mother's stomach was unique among all frogs. Common names The common names, "gastric-brooding frog" and "platypus