A fossil uncovered on a Melbourne beach belonged to a giant prehistoric bird with a five-metre wing span and serrated beak, scientists report.
The five million-year-old lower leg bone provides the first evidence the ancient sea bird once soared across Australia's skies.
A Museum Victoria palaeontologist, Erich Fitzgerald, who lead the analysis of the specimen, said the discovery meant the species, pelagornis, which lived for more than 50 million years before going extinct about 2.5 million years ago, existed on all continents.
The ancient feathered creatures, known as bony-toothed birds for the sharp, teeth-like serrations along their beak, were the largest flying animal to exist on Earth after the extinction of pterosaurs, a flying reptile that lived during the time of the dinosaurs, 65 million years ago.
''The wing span of these birds was as great as the height of a giraffe,'' Dr Fitzgerald said.
The small leg bone was uncovered on a Museum Victoria field trip to Beaumaris, a suburb of Melbourne, where fossils of ancient seals, dugongs and giant sharks the size of a city bus have also been found, in 2004.
The specimen, encased in sandstone, remained unstudied until Museum Victoria fossil bird expert and PhD student Travis Park and University of Adelaide researcher Trevor Worthy joined Dr Fitzgerald's to investigate the fossil last year.
The pelagornis was just one of the many giant sea creatures that existed in Australia five million years ago, the same time giant marsupials, or mega fauna, and early humans roamed the land.
''When pelagorins was soaring the skies of the world our hominid ancestors were alive and well in east Africa,'' Dr Fitzgerald said.
But after more than 100 years of research, the species' closest ancestors were ''hotly debated'' among scientists, he said.
''Although they have some characteristics that suggest relation to pelicans, other features hint at affinities to albatrosses,'' he said.
While the exact cause of the creature's demise was unknown, environmental factors were believed to have played a role, Dr Fitzgerald, whose findings are published in the Journal of Vertebrate Paleontology, said.
''We know that about the time the animal went extinct there were some major shifts in the Earth's climate.''
- The Age
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