Apatosaurus was formerly known as Brontosaurus. Although smaller in size than the Diplodocus, this animal looked much heavier at 30 tons. Little information has come down to us about its life as well as that of the Diplodocus. For many years, the common belief among scientists was that Apatosaurus climbed on its hind legs to get food, leaning on its tail. However, recent research has proven that these animals had no flexible neck, so by resting on all four paws, it could only extend its neck five meters above the ground. Apatosaurus was most likely protected by sharp claws on its front paws and a tail. Allosaurus bite marks on the Apatosaurus bones indicate either that predators attacked this giant, or that its dead body was mauled by an Allosaurus.
The first fossilized Apatosaurus bones, without the skull, were found in 1877, but the first complete dinosaur skeleton was not assembled until 1975.

Maximal length: 25m
Age: Late Jurassic
Fossil record: North America (Western United States)