Size and Weight:
It took paleontologists a long time to figure out exactly what type of dinosaur Anatotitan was. Since the discovery of its fossil remains in the late 19th century, this giant plant-eater has been classified in various ways, sometimes going by the now-unfashionable names Trachodon or Anatosaurus, or considered a species of Edmontosaurus. However, in 1990 a convincing case was presented that Anatotitan deserved its own genus in the family of large, herbivorous dinosaurs known as hadrosaurs, an idea that has since been accepted by most of the dinosaur community. (A newer study, however, insists that the type specimen of Anatotitan was really a superannuated specimen of Edmontosaurus, hence its inclusion in the already-named species Edmontosaurus annectens.)
As you might have guessed, Anatotitan ("giant duck") was named after its broad, flat, duck-like bill. However, one shouldn't take this analogy too far: the beak of a duck is a very sensitive organ (a bit like human lips), but Anatotitan's bill was a hard, flat mass used mainly to dig up vegetation. Another odd feature of Anatotitan (which it shared with other hadrosaurs) is that this dinosaur was capable of running clumsily on two legs when it was chased by predators; otherwise, it spent most of its time on all four feet, munching peacefully on vegetation.