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An artist's illustration of Bullockornis planei
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Superorder: Aves
Order: Anseriformes
Family: Dromornithidae
Genus: Bullockornis
P. Rich, 1979
Species: B. planei
Binomial name
Bullockornis planei
P. Rich, 1979

Bullockornis, colloquially known as the "Demon Duck of Doom" or "Thunderbird", was a large flightless bird from the middle Miocene period, which was endemic to Australia.

This bird measured 2.5 metres (8 feet) tall and weight approximately 250 kilograms (550 lbs). Bullockornis possessed a large beak which was designed to shear. This design has lead scientists to believe that this animal was carnivorous.

Many palaeontologists believe that Bullockornis is related to ducks and geese. This, as well as its size and diet, have earned it its nickname. It has also been mistranslated on multiple occasions, with people believing that its name means "ox-bird". However, its name is actually derived from Bullock Creek, Australia, the fossil site where Bullockornis was discovered.