''Ilbandornis'' was a genus of

ostrich Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There ...

-sized

dromornithid Dromornithidae, known as mihirungs and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene Epochs. All are now extinct. They were long classified in Struthioniformes, ...

. It was far more lightly built than other members of the family, indicating a more

cursorial A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often us ...

lifestyle. The majority of researchers consider Dromornithids to be herbivorous; this is borne out by molecular analysis of the

gastroliths A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In oth ...

and eggshells of both ''Ilbandornis'' and the related ''

Genyornis ''Genyornis newtoni'', also known as thunder bird and mihirung paringmal (meaning "giant bird"), is an extinct species of large, flightless bird that lived in Australia during the Pleistocene epoch until around 50,000 years ago. Over two met ...

''. While ''Ilbandornis'' and ''

'' have skulls of similar size to emus, other Dromornithids such as '' Bullockornis'' and ''

Dromornis ''Dromornis'' is a genus of large to enormous prehistoric birds. The species were flightless, possessing greatly reduced wing structures but with large legs, similar to the modern ostrich or emu. They were likely to have been predominantly, i ...

'' have far more robust skulls with large beaks; these were previously considered an adaptation for carnivory, but their blunt edges and lack of hooked tip indicate that the species were herbivorous. It is therefore likely that the differences in skull shape are due to differences in diet. There are currently two species included in the genus, ''Ilbandornis lawsoni'' and ''Ilbandornis woodburnei''. Both are known from the Alcoota Fossil Beds in the

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Aust ...

, from Waite Formation sediments dating to the Late Miocene.Rich, P. (1979): The Dromornithidae, an extinct family of large ground birds endemic to Australia. ''Bureau of National Resources, Geology and Geophysics Bulletin'' 184: 1–196. The local fauna at the alcoota site includes another dromornithid species, the gigantic ''

Dromornis stirtoni ''Dromornis'' is a genus of large to enormous prehistoric birds. The species were flightless, possessing greatly reduced wing structures but with large legs, similar to the modern ostrich or emu. They were likely to have been predominantly, i ...

''.

References

Dromornithidae Extinct flightless birds Miocene birds of Australia Miocene birds Prehistoric bird genera {{paleo-bird-stub