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The southern gastric brooding frog, also known as the platypus frog, was discovered in 1973 and is now believed to be extinct. It was last seen in the wild in 1981. The distribution of this species was restricted to above 300 m in the Conondale and Blackall Ranges of south-east Queensland.
The southern gastric brooding frog was about 5 cm long, had smooth skin and was brown on its back and pale cream to white underneath. It was an aquatic species that lived in or very close to rocky creeks, streams and adjacent rock pools in rainforests. It had webbed toes and eyes on the top of its head, both adaptive features for its aquatic life.
Another gastric brooding frog, the northern gastric brooding frog, 'Rheobatrachus vitellinus', was discovered in 1984 in rainforests in Eungella, near Mackay on the central Queensland coast. It has subsequently disappeared and may also be extinct.
When the first known gastric brooding frog, 'R silus', was discovered it was named after its unique breeding habit of developing its young in the mother's stomach. The female frog presumably swallowed the fertilised eggs and the tadpoles hatched and developed in her stomach, feeding on their large egg yolks. After some weeks, the young emerged from the mother's mouth as fully formed froglets.
Gastric brooding frogs had specialised features that enabled their unusual brooding of the young in the mother's stomach. The mother's digestive stomach acids ceased being produced during brooding, and the wall of the mother's stomach became thinner and more elastic to help the developing young.
The disappearance of the gastric brooding frogs highlights the potential loss to humans of valuable information and resources when species become extinct. In addition to the potential for development of disease-fighting drugs and vaccines for humans, the gastric ability of these frogs fascinated scientists because of its biological significance. The loss of these two species, like the extinction of other plants and animals, highlights how the loss of biodiversity can affect human life. Scientists are concerned about the human influence on the rate of extinction of plants and animals worldwide.
The reason the southern gastric brooding frog disappeared is unknown. Researchers have found no evidence of pollution, habitat disturbance or other environmental changes that account for its decline. Frog populations have declined worldwide, however, and many species have been affected by chytridiomycosis, a disease caused by a fungus. This disease may have also been responsible for the decline of the southern gastric brooding frog.