Image: Opalised jaw of Steropodon, backlit
Steropodon galmani Archer. One of Australia's oldest mammal fossils, from the Early Cretaceous rocks at the opal fields of Lightning Ridge, New South Wales.
- Carl Bento
- © Australian Museum
Steropodon galmani, a platypus-like monotreme from the Early Cretaceous, was the first Mesozoic mammal discovered in Australia. It is known from this opalised lower jaw with molar teeth. The teeth of Steropodon are similar to those of later fossil platypuses although its molars are more archaic in form.Steropodon lived alongside dinosaurs, crocodiles, early birds and other early mammals on the forested shores of the inland Cretaceous Eromanga Sea.