The extinct creature’s bizarre mix of features are reminiscent of platypuses and echidnas

The Australian platypus is one of Earth’s most unusual creatures — but there was a time when it might not have stood out in a crowd. In roughly 100-million-year-old rocks in Australia, scientists have unearthed three new species of monotremes, a group of egg-laying mammals that today include only the platypus and another Australian oddball, the echidna.

The fossil discoveries double the number of known monotreme species during this brief span of the Cretaceous Period, hinting at a bygone Age of Monotremes.

Australia today is thought of as a land of marsupials, mammals that nurture developing young in pouches, including kangaroos, koalas and wombats. But a whole “civilization” of diverse monotremes, ranging from pig-sized to rat-sized, may have radiated across the continent first.

The modern platypus, native to eastern Australia and Tasmania, is one of the weirdest creatures on Earth (SN: 12/3/14). The creatures have a toothless, ducklike bill, a beaverlike tail and otterlike feet; their bills are also electro-sensory organs that allow them to detect prey in murky waters. Male platypuses even produce venom, delivered via spurs on the rear feet. The platypus’ Frankensteinian combination of parts was so surprising to 18th century European biologists that many initially thought it to be a hoax.