Anatotitan was a "bird-hipped" dinosaur from the group known as the duck-billed dinosaurs or hadrosaurs. It had long, powerful back legs with three hoof-like toes and small, more delicate front limbs, with a mitten-like covering on its hands. It grazed on all fours but could rear up onto its hind legs on occasion.

The front of Anatotitan's jaw formed a long wide beak. Further back, it had batteries of strong cheek teeth. It had a good chewing action with hundreds of teeth forced to rub abrasively past one another. Like Iguanodon, it had a sturdy tail and stocky neck.

Evidence for this dinosaur comes from three skulls and partial skeletons found in Hell Creek, Montana, and other finds in South Dakota, in the USA. Recently palaeontologists have suggested that Anatotitan may just be a large Edmontosaurus. Three species of Edmontosaurus have been identified in the same area but are one metre shorter and weigh one tonne less.