An ancient whale fed by sucking small animals from mud at the bottom of the ocean, experts say.
The Mammalodon lived around 25 million years ago, and is related to today's blue whales - the largest animals on Earth.
The ancient animal's mud slurping is a bit like the way modern baleen whales eat by filter feeding.
These whales strain tiny sea creatures through special "combs" which take the place of teeth.
Unlike modern baleen whales the Mammalodon still had teeth.
Scientists think it used its snout to suck its prey from the mud on the ocean floor before eating them.
You can see the Mammalodon's fossilised teeth
They are hoping this discovery will help them understand how some whales developed to become filter feeders, while others kept their teeth.
The Mammalodon colliveri fossil was found in Torquay, in Victoria, Australia.
Although it was unearthed in 1932 it is only recently that scientists have studied the way it might have fed.