World's Largest Extinct Animal

The Argentinosaurus is arguably the largest dinosaur that ever lived. It measured 120 feet long and 70 feet tall. It weighed about 100 tons. Only incomplete fossils were found which include vertebrae, sacrum, tibia, and broken ribs. Discovered in 1987 by a local rancher in Argentina, the bones are huge -- some measuring five feet high and five feet wide. By extrapolating from the size of the bones, paleontologists were able to determine the Argentinosaurus' size. These dinosaurs lived 93 to 100 million years ago during the middle Cretaceous period. These animals were plant eaters.

The longest dinosaur called the Seismosaurus measured between 130 and 170 feet in length and is arguably one of the longest animals. Not the heaviest dinosaur, these sauropods weighed a lightweight of 30 tons and stood only 18 feet tall. These dinosaurs used their tails like whips to defend themselves. Seismosaurus lived 145 to 156 million years ago during the late Jurassic period. These animals were plant eaters.

The giant ichthyosaur Shonisaurus sikanniensis measured around 21 meters or about 70 feet in length, making it the largest extinct ocean animal. It lived during the late Triassic or about 201 to 235 million years ago. Ichthyosaurs ate fish and squid primarily, but may have eaten larger vertebrates.

The largest land mammal was the Paraceratherium, which stood at a height of 5.5 meters or 18 feet at the shoulder and 10 meters or more that 30 feet long. This was a giraffe-like animal that ate primarily plants in the Oligocene period, 23 to 34 million years ago.

The largest extinct bird is the Dromornis stirtoni of Australia. These birds stood nine meters or ten feet in height and weighed 500 kg or more than 1100 pounds. These flightless birds may have been plant eaters but some scientists believe they may have eaten meat, according to the Australian Museum. They lived during the late Miocene period about five to 11.6 million years ago.