Hypacrosaurus is most easily distinguished from other hollow-crested duckbills (lambeosaurines) by its tall neural spines and the form of its crest. The neural spines, which project from the top of the vertebrae, are 5 to 7 times the height of the body of their respective vertebrae in the back,[4] which would have given it a tall back in profile. The skull's hollow crest is like that of Corythosaurus, but is more pointed along its top, not as tall, wider side to side, and has a small bony point at the rear.[4] Unlike other lambeosaurines, the passages for the airways do not form an S-curve in the crest (at least not in H. altispinus).[5] The animal is estimated to have been around 9.1 meters long (30 feet),[4] and to have weighed up to 4.0 tonnes (4.4 tons).[6] As with most duckbills, its