The species lived during in the middle and upper Miocene about 5–15 million years ago. Wear on the tooth shows that it probably crushed hard shells such as those of turtles. Because of this, scientists believe that "O. tharalkooschild" was carnivorous. They also believe that it was twice the size of the modern platypus at one metre long. Its name was chosen in honour of an indigenous Australian creation story for the platypus, where a duck named Tharalkoo gives birth to a strange and fantastic creature after being ravished by a water-rat.