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For more than a century, scientists have been unsuccessful in finding skull fossils of the thunderbird species Genyornis newtoni. About 50,000 years ago, these titans, also known as mihirungs, from the Aboriginal term meaning “giant bird”, roamed the forests and grasslands of Australia on their muscular legs. They were taller than humans and weighed hundreds of pounds.
The last of the Mihirungs disappeared about 45,000 years ago. The fact that the only skull found in 1913 was missing and severely damaged raised questions about the giant bird’s face, habits and ancestors.
Now, the discovery of a complete G. newtoni skull has solved this long-standing mystery, giving scientists their first face-to-face encounter with the giant mihirung.
And he has a very strange goose face.
G. newtoni was about 2 meters tall and weighed up to 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 paleontologists unearthed a large G. newtoni fossil in southern Australia’s Lake Callabonna, discovering multiple skull fragments, a skeleton, and an articulated skull, providing the first evidence of the bird’s upper beak. This abundance shed new light not only on G. newtoni but also on the entire dromornithid group that is linked 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, new fossils and reconstructions provide critical missing details, said Larry Witmer, an anatomy and paleontology professor at Ohio University who was not involved in the research.
“The skull is always the prize because there is so much important information inside the head,” Witmer said in an email. “This is where the brain and sensory organs are located, this is where the feeding apparatus is located, and typically this is where the vision organs (horns, crests, wattles and combs, etc.) are located,” he said. “In addition, their skulls are full of structural features that give us clues about their family tree.”
In the new study, “the authors got everything they could out of these new fossils,” Witmer said. The researchers didn’t just model the bones in the skull; They also analyzed the placement of jaw muscles, ligaments and other soft tissues that hint at the bird’s biology.
“This latest discovery of new Genyornis skulls has really helped fill in the gaps,” Witmer said.
‘Very goose-like’
Lead study author Phoebe McInerney, a vertebrate palaeontologist and researcher at Flinders University, said the newly discovered skull took center stage in the digital reconstruction, supported by data from other skull fossils and modern birds, offering previously unknown clues about G. newtoni’s appearance. South Australia.
“Only now, 128 years after its discovery, can we say what it actually looked like,” McInerney said in an email. “Genyornis has a very unusual beak that resembles a goose.”
Compared to the skulls of many other birds, the skull of G. newtoni is quite short. However, the jaws are very large and supported by strong muscles.
“They would have a very wide range,” McInerney said.
The skull also hinted at G. Newtoni’s diet. A flat gripping area on the beak was suitable for shredding soft fruit, tender shoots and leaves, and the flattened palate on the underside of the upper beak may have been used to crush fruit into pulp.
“We knew from other evidence that they probably ate soft foods, and the new beak supported that,” McInerney said. “The skull also showed evidence of some adaptations to feeding in water, perhaps on freshwater plants.”
Witmer said this underwater feeding suggestion was unexpected, given G. newtoni’s enormous size.
“Perhaps this shouldn’t be too surprising, given that dromornithids like Genyornis are related to the group that includes ducks and geese, but Genyornis was 6 to 25 feet tall and weighed perhaps as much as 500 pounds,” Witmer said. Additional fossil discoveries could help resolve the question of whether such adaptations are untapped traits inherited from aquatic ancestors, or whether “these giant birds simply moved into shallow waters in search of soft plants and leaves.”
‘A strange combination’
The reconstruction helped scientists resolve the conflicting lineage of dromornithids, placing them in the waterfowl order Anseriformes, the study authors reported. Based on their bone structure and associated muscles, it turns out that dromornithids were likely close relatives of the ancestors of modern South American shriekers (duck-like birds) that lived in wetlands in southern South America.
Although G. newtoni had a goose-like beak, its face was not a perfect match for that of modern geese, said Jacob Blokland, an avian paleontologist and co-author of the study. A researcher from the Flinders Palaeontology Group at Flinders University in Blokland illustrated reconstructions of the skull and G. newtoni in life.
“I was surprised at how superficially creepy it looked, with its large spatula beak, but it certainly didn’t look like any of the geese we have today,” Blokland said in an email. “It has aspects reminiscent of parrots, to which it is not closely related, as well as land birds, which are much more closely related. “In some ways it looks like a strange mix of very different-looking birds.”
For the new reconstruction, Blokland started with the bony outer ear region, he said, “because there were several specimens that preserved this part.” From there he built a scaffolding consistent with multiple skull fossils. Some areas of the reconstruction were based on skulls from other dromornithids or modern waterfowl, and anatomical studies of modern birds gave clues about how muscles and ligaments might move bones.
One previously unknown detail was a large triangular bony shield called a helmet located on the upper beak, which may have been used for sexual displays, the study authors reported.
McInerney said large, flightless emus and cassowaries – not close relatives of thunderbirds – now roam Australia, but cast a much smaller shadow than the long-lost mihirungs and still loom large in the popular imagination. He added that there is much that has yet to be discovered about the anatomy of these extinct giants, such as how inner ear structures associated with head stabilization and movement may have been affected by their gigantism and inability to fly.
Blockland said that while the new view of G. newtoni is the most accurate to date, additional fossils will bring into sharper focus the portrait of this unusually giant goose – the last of the powerful thunderbirds – and its vanished habitat.
“Such a giant and unique bird undoubtedly impacted the environment and other animals, large and small, with which it interacted,” he said. “Only through study can we create a bigger picture and discover what we are currently missing.”
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazines.
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