Researchers have hailed the discovery of an ancient whale species in Australia's south-east as a milestone in marine science.

Axar.az reports, citing ABC, found near Jan Juc on Victoria's Surf Coast in 2019, the fossil of a baleen whale has today been described as the Janjucetus dullardi — an "entirely new species of prehistoric whale".

"This is a whale that was unknown to science," Erich Fitzgerald, senior curator of vertebrate palaeontology at the Museums Victoria Research Institute said.

"What is really significant about this new species of fossil whale is that it actually is an ancient ancestor of today's baleen whales, and that includes gentle giants like humpback whale and blue whale."

The Janjucetus dullardi lived 25 million years ago and belongs to an extinct genus of baleen whales — which instead of teeth, have baleens, or hard plates, attached to their jaws — called Mammalodontids.

But unlike others in the family, the new species named on Wednesday has big eyes, sharp teeth and is just over 2 metres in length, a tiny size by whale standards.

Scientists behind the study said it appeared the Janjucetus dullardi was built for hunting and would have been a fearsome predator in ancient Victorian seas.

"It's essentially a little whale with big eyes and a mouth full of sharp, slicing teeth … small and deceptively cute, but definitely not harmless," said Ruairidh Dunac, a PhD student at Monash University.