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For more than a century, scientists have been unsuccessful in hunting down fossil skulls for the Genyornis newtoni species of thunderbird. About 50,000 years ago, these titans, also known as mihirungs, from an Aboriginal term for “giant bird,” roamed the forests and grasslands of Australia on muscular legs. They stood taller than humans and weighed hundreds of kilograms.
The last of the mihrungs became extinct around 45,000 years ago. The only skull, found in 1913, was incomplete and badly damaged, raising questions about the giant bird’s face, habits and ancestry.
Now, with the discovery of a complete G. newtoni skull, this long-standing mystery has been solved, bringing scientists their first face-to-face encounter with the giant mihirung.
And he has a very strange goose face.
G. newtoni was about 7 feet (2 meters) tall and weighed up to 529 pounds (240 kilograms). It belonged to the family Dromornithidae, a group of flightless birds known from fossils found in Australia.
Between 2013 and 2019, a team of Pota Oir paleontologists discovered the fossil G. newtoni in Lake Callabonna in southern Australia, finding multiple skull fragments, a skeleton and an articulated skull that provided the first evidence of the bird’s upper bill. This bonanza shed new light not only on G. newtoni, but also on the entire dromornithid group, linking it to modern waterfowl such as ducks, swans and geese, scientists reported Monday in the journal Historical Biology.
Although scientists have known about Genyornis for more than a century, the new fossils and reconstruction provide critical missing data, said Larry Witmer, a professor of anatomy and paleontology at Ohio University who was not involved in the research.
“The skull is always the prize because there is so much important information in the head,” Witmer said in an email. “It is where the brain and sense organs are located, where the feeding apparatus is located, and usually where the display organs (horns, crests, wattles and combs, etc.) are located ,” he said. “Additionally, skulls tend to have structural characteristics that give us clues about their lineage.”
In the new study, “the authors nailed these new fossils for all they had,” Witmer said. The researchers didn’t just model the bones in the skull; they also analyzed the location of the jaw muscles, ligaments, and other soft tissues that provided clues to the bird’s biology.
“This latest discovery of new Genyornis skulls really helped fill in the gaps,” Witmer said.
‘Very like a goose’
The newt’s skull takes center stage in a digital reconstruction, supplemented by other skull fossils and data from modern birds, and offers previously unknown clues about what G. newtoni looked like, the study’s lead author said. Phoebe McInerney, vertebrate paleontologist and researcher at Flinders University i. South Australia.
“Until now, 128 years after its discovery, we can say what it really was,” McInerney said in an email. “Genyornis has a very unusual beak that is very goose-like.”
Compared to the skulls of most other birds, the skull of G. newtoni is quite short. But the jaws are huge, supported by powerful muscles.
“They would have a very wide gap,” McInerney said.
The skull also provided a clue to the diet of G. newtoni. A flat grip zone in the beak was suitable for tearing soft fruit and tender shoots and leaves, while a cleft palate on the underside of the upper bill could have been used to crush fruit into a pulp.
“We knew from other evidence that they probably ate soft food, and the new beak supported that,” McInerney said. “The skull also showed some evidence of adaptations to water feeding, possibly on freshwater plants.”
This suggestion of underwater feeding is not unexpected, given the enormous size of G. newtoni, Witmer said.
“Perhaps that shouldn’t be too surprising since dromornithids like Genyornis belong to the group that includes ducks and geese, but Genyornis was six or seven feet tall and may have six as big as 500 pounds,” Witmer said. Additional fossil discoveries may help resolve whether those adaptations were unused features inherited from aquatic ancestors, “or whether these giant birds were venturing into the shallows in search of soft plants and leaves.”
‘strange connection’
The reconstruction helped the scientists resolve the conflicting lineage of doromannithids, placing them within the waterfowl order Anseriformes, the study’s authors reported. Based on related bone and muscle structures, dromornithids were probably closely related to the ancestors of modern South American shrews, duck-like birds living on wetlands in southern South America.
Although G. newtoni had a goose-like beak, its face was not a perfect match for modern geese, said study co-author and avian paleontologist Jacob Blokland. A researcher with the Flinders Palaeontology Group at Flinders University, Blokland showed reconstructions of the skull and G. newtoni in life.
“I was surprised at how small it looked, with its large, spacey bill, but certainly unlike any goose we have today,” Blokland said in an email. “There are certain features that remind the parrots, which are not closely related, but also ground birds, which are much closer relatives. In some ways it seems like a strange amalgamation of very different birds.”
For the new reconstruction, Blokland started with the bony outer ear region, “because there were some specimens that preserved this part,” he said. From there, he built a scaffold that was consistent across multiple skull fossils. Some areas of the reconstruction were based on skulls belonging to other dromornithids or modern waterfowl, and anatomical studies of modern birds revealed how muscles and ligaments could move the bones.
One previously unknown detail is a broad triangular bony shield called a casque on the upper bill, which may have been used for sexual displays, the study authors reported.
Great flightless vultures (not closely related to thunderbirds) roam Australia at present, but they cast a far smaller shadow than the long-lost mihrungs, which still loom large in the popular imagination, McInerney said. Much about the anatomy of these extinct giants remains to be discovered, she said, such as how gigantism and flightlessness may have affected inner ear structures involved in head stabilization and head movement.
And while the new view of G. newtoni is the most accurate to date, additional fossils will shed more light on the portrait of this unusual gargantuan goose — the last of the mighty thunderbirds — and its vanished habitat, Blockland said. .
“Such a huge and unique bird certainly affected the environment and other animals it interacted with – big and small,” he said. “Only through study can we build a bigger picture, and find out what we are missing now.”
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine.
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