Genyornis is an extinct group of large, flightless birds that lived in Australia during the Pleistocene Epoch until about 40,000 to 50,000 years ago. These birds were over two meters tall and probably ate plants. Genyornis was the last known bird in the extinct family Dromornithidae, which lived in Australia for more than 30 million years. It is not closely related to birds like emus, but it is thought to be a large type of bird similar to chickens, likely an early group in the same family as ducks and geese. Genyornis and many other large animals in Australia became extinct during the Late Pleistocene extinction event, which happened around the same time humans arrived in the region. Evidence shows that humans ate Genyornis eggs, making it one of the few Australian megafauna species for which human interaction has been proven.

Taxonomy and evolution

The species Genyornis newtoni was first described in 1896 by Edward Charles Stirling and A. H. C. Zeitz. They named it after Alfred Newton, a Cambridge professor. The genus name comes from the Greek words "génus," meaning "jaw or chin," and "órnis," meaning "bird." This is because the lower jaw of Genyornis was quite large. The fossil found is a left femur, a leg bone. It was discovered at Lake Callabonna in South Australia. Zietz led the excavation and described it. The findings were reported in the journal Nature, which also found marsupial fossils there.

Many bird fossil pieces were found in the clay near diprotodont fossils. Later, more complete fossils, including skulls, were uncovered. The paper reviewed earlier descriptions of ostrich-like bird fossils in Australia. These were either grouped with ancient emus (Dromaius) or the only known Dromornis species, D. australis.

In 1893, George Hurst wrote a letter about finding part of a Genyornis skeleton. This made Stirling aware of the species. The family to which Genyornis belongs, Dromornithidae, is generally considered a type of large bird. However, scientists have debated its exact classification. A 2024 study placed Dromornithidae in the Anseriformes group, which includes ducks and geese. They are closely related to South American screamers (Anhimidae).

The earliest evidence of this group is footprints from over 55 million years ago in Queensland. These footprints belong to a large, flightless bird with a foot structure similar to Genyornis. The oldest known bones of dromornithids are from about 25 million years ago. During the Miocene, many dromornithid species lived together, including Dromornis, some of the largest birds ever. However, the family declined over time, and by the Late Pleistocene, only Genyornis newtoni remained.

Cladogram of Dromornithidae after McInerney et al. 2024
Ilbandornis woodburnei

Description

Genyornis newtoni was a medium-sized dromornithid with a strong body, standing up to 2.15 metres (7.1 ft) tall and weighing about 250–350 kilograms (550–770 lb). Scientists may estimate its weight differently depending on the method used. It was larger than Ilbandornis but smaller than Dromornis stirtoni and Dromornis planei in both height and weight. Fossils of this species have been found still connected in the correct position, a feature not seen in any other dromornithid. Egg remains linked to this species have an average size of 15.5 by 12.5 cm. Stones found with the bones, called gastroliths, helped scientists understand where some fossils were buried, as they were sometimes shallow.

Before 2024, scientists mostly used the skulls of related species to rebuild Genyornis’s head because the original skull was badly damaged. However, a 2024 study, using a newly found, well-preserved skull, showed Genyornis’s head looked very different from earlier ideas. Its beak was more like a goose’s, with a raised, triangle-shaped structure on top. This beak was unlike those of other mihirungs and may have helped the bird eat underwater plants. Other traits, such as possible protection for the ears and throat, might have also helped it feed underwater.

Distribution

Fossils of the mihirung have been discovered in South Australia and New South Wales, and they are from the Pleistocene Epoch. Genyornis newtoni is the only known species of dromornithid that lived during the Pleistocene.

Extinction

Two main ideas explain why large animals, called megafauna, disappeared. One is human activity, and the other is changes in climate. A study examined over 700 pieces of Genyornis eggshells. Scientists found that Genyornis declined and went extinct quickly, too fast to be caused by climate changes. This led researchers to believe that human activity, not climate, was the main reason for the extinction of many large animals in Australia.

In 2015, scientists studied Genyornis eggshells from 200 locations. They found burn marks on the shells, which suggested the eggs were cooked over fires. Chemical analysis showed the heat levels matched those from an ember fire. The eggshells were dated to between 53,900 and 43,400 years ago, showing humans may have collected and cooked Genyornis eggs long before the species went extinct. Later, another study suggested the eggs might have belonged to a different extinct bird called the giant malleefowl.

A 2022 study looked at the protein structure of the eggshells. Using a method called phylogenetic analysis, scientists concluded that the eggs came from a group of birds that split off from megapodes before they evolved. This supported the earlier idea that the eggs were from Genyornis. Researchers noted that humans may have used Genyornis eggs in a way similar to how they used ostrich eggs in other parts of the world during the Pleistocene, but they could not confirm how much humans interacted with Genyornis.

A 2021 study compared the possible extinction rates of Genyornis to those of emus and Australian brushturkeys. If Genyornis eggs were consumed at similar rates, the species would have gone extinct much faster than these still-living birds.

In 2010, archaeologists found a rock painting in the Northern Territory that may be 40,000 years old. They believed it showed two Genyornis birds. In 2011, Aboriginal traditions suggested Genyornis survived longer in southwest Victoria. However, later research found the painting was no older than 14,000 years, long after the bird was thought to have gone extinct, and it looked similar to other bird depictions.

A 2022 study of fossils from Lake Callabonna showed that Genyornis died out around 50,000 years ago. The lake dried up due to climate changes, and the birds suffered from a bone disease called osteomyelitis, likely caused by getting stuck in the drying mud. When the lake disappeared, the birds lost their main water source and died.

A 2024 study of Genyornis skulls found features that suggest the birds ate aquatic plants. This reliance on freshwater habitats may have made them especially vulnerable to the loss of lakes during Australia’s drying climate in the late Pleistocene, which could have caused their extinction.