Long after the extinction of dinosaurs, a giant toothed bird soared across the Australian skies, according to scientists.

The conclusion was drawn after paleontologists studied a five-million-year-old pelagornis bone found on Melbourne beach. The bone is part of the bird's lower leg.

The remarkable fossil was found about 20km southeast of Melbourne in 2004. It was the first pelagornis fossil ever dug up in Australia. Ancient pelagornis traces had previously been found in every other continent around the world.

Museum Victoria's art rendition of the Pelagornis

"Our pelagornis bone is similar in size to that of the pelagornis from Chile, which had a wingspan of at least five metres," said Dr Erich Fitzgerald of Museum Victoria.

"The wing span of these birds was as great as the height of a giraffe," Dr Fitzgerald said. He noted, "That is twice the size of the largest albatross alive today. So, we now know that there were once birds with teeth soaring over coastal Victoria with a wingspan greater than the length of a Toyota LandCruiser."

The prehistoric bird species is said to be the largest flying animal to soar in the planet 65 million years ago. When dinosaurs still walked the Earth, pterosaurs ruled the skies.

Scientists have no specific theories as to what could have caused the extinction of pelagornis, but major changes in the Earth's climate were suspected to be contributing factors.

"We know that about the time the animal went extinct there were some major shifts in the Earth's climate," said Dr Fitzgerald.

A story on the Melbourne pelagornis fossil is featured in the Journal of Vertebrate Paleontology.