By TORSTEN BLACKWOOD / AFP The future of the platypus, a unique duck-billed, egg-laying mammal only found in Australia, is under threat because they cannot climb over tall river dams, according to a new study. The future of the platypus, a unique duck-billed, egg-laying mammal only found in Australia, is under threat because they cannot climb over tall river dams, according to a new study. The platypus is an oddity in many ways. As well as its duck-like bill and egg-laying, it is a rare venomous mammal, brandishing centimetre-long poisonous spurs on its hind legs. They are also one of the only…