Ancient geese stood three meters tall and weighed as much as a cow!

ADELAIDE, Australia (PNN) - June 3, 2024 - A rare fossil skull provides strong evidence that the Dromornithidae, an extinct group of Australian flightless birds, were related to geese and ducks.

Australia’s prehistoric thunder birds - once thought to be the ancestors of emus - were, in fact, the biggest geese that ever lived.

The group has been reclassified following the analysis of a 45,000-year-old Genyornis newtoni skull found in a fossil deposit at Lake Callabonna in the South Australian desert.

The newly discovered skull is the first from the extinct species found since 1913 and the only one preserved well enough to allow detailed anatomical study. It is thought that Genyornis newtoni weighed about 230 kilograms and stood over 2.5 meters tall.

However, its close relative, Dromornis stirtoni, reached heights well over 3 meters and weighed up to 600 kilograms, making it not just a contender for biggest bird ever, but by far the largest goose.

When the first thunder bird fossils were found in the 19th Century, they were thought to be the ancestors of the ratites, which include emus, cassowaries and ostriches. Others have since argued that the group, formally called the Dromornithidae and comprising eight known species, should be categorized as land fowl, which includes chickens and pheasants.

Now, Phoebe McInerney at Flinders University in Adelaide, Australia, and her colleagues have determined that thunder birds were giant waterfowl and should be moved into the same group as geese, the Anseriformes.

The team was mainly convinced by the anatomy of the beak and skull, including the arrangement of muscles and modifications to the bone where they attach. The structure in Genyornis is near-identical to that of an old waterfowl lineage, the South American screamers. This structure is extremely complex and is unlikely to have evolved independently, says McInerney.

All the thunder birds were vegetarians, she says, though they were probably fierce creatures. “I think they would have been very tough animals,” says McInerney. “They would have been able to defend themselves and would have been quite overwhelming beasts. They would have made very deep and loud calls.”

Adam Yates at the Museum and Art Gallery of the Northern Territory, Australia, says the study is a vindication of his predecessor, Peter Murray, who proposed in the early 1990s that the thunder birds were waterfowl. “So, it’s not a shock to me,” says Yates. “But a skull of Genyornis has been hard to find, so it’s great to see its skull finally revealed.”

Many thunder bird species died out prior to the arrival of humans in Australia around 65,000 years ago, with this most likely cause to have been due to climate change. However, G. newtoni and humans overlapped on the continent for tens of thousands of years and some researchers speculate that hunting also played a role in their demise.