Largest organisms were related to the ostrich. They exceeded in height and . The last of the elephant birds became extinct about 300 years ago. Of almost exactly the same upper proportions as the largest elephant birds was "Dromornis stirtoni" of Australia, part of a 26,000-year-old group called mihirungs of the family Dromornithidae. The largest carnivorous bird was "Brontornis", an extinct flightless bird from South America which reached a weight of and a height of about . The tallest carnivorous bird was "Kelenken", which could reach 3 to 3.2 meters in height and 220 to 250 kilograms. The tallest bird ever was
Largest organisms the giant moa ("Dinornis maximus"), part of the moa family of New Zealand that went extinct around 1500 AD. This particular species of moa stood up to tall, but weighed about half as much as a large elephant bird or mihirung due to its comparatively slender frame. The heaviest bird ever capable of flight was "Argentavis magnificens", the largest member of the now extinct family Teratornithidae, found in Miocene-aged fossil beds of Argentina, with a wingspan up to , a length of up to , a height on the ground of up to and a body weight of at least