The Ananotitan(now known as Edmontosaurus annectens) has contributed to giving the hadrosaurs their generic appearance and overall name, this is because of the large duck like bill this animal exhibited. The Anatosaurus was a hadrosaur that thrived during the late Cretaceous and was one of the main prey items of the fearsome Tyrannosaurus rex, one of their main defenses against such a formidable predator was their ability to communicate using a complicated array of vocalizations that warned other individuals in the herd of danger. As well they relied on their sheer numbers, sticking together for protection and social interaction. If given the choice of fight or flight this animal would mostly take the option of running away rather than fighting because of their general lack of external defensive features, though some induviduals grew to rather large sizes. Hadrosaurs had a body design which is more adapted for grazing rather than having defenses such as spiky tails or large horns. Edmontosaurs' bill is one of the largest of any hadrosaur and is perfectly designed for slicing vegetation like a pair of scissors. It's theorized (though rather speculative) that the bill may have sported an air sac which was present in male Anatosaurs and was used for display purposes, males with the biggest and most brightly colored air sacs would've been more likely to attract mates as it shows signs of strong genetics which are vital to the survival of the specie's gene pool and genetic diversity. In regards to the exact classification of this animal, it is often refferred to as Edmontosaurus annectens and others calling it Anatosaurus. for the most part both names pertain to the same species and so the names are synonymous to each other.