|Name Translation||Of the Latin magnus, "large", and the first name of Paul G. Haaga, Jr.|
|Location||México, Baja California|
|Size||54.1 ft (16.5 m)|
|Date of Discovery||1968-1974 discovered, 2012 named|
Magnapaulia is noted for its great size and the tall profile of its tail, which had elongated chevrons and vertebral spines like those of Hypacrosaurus. Its size was estimated by its original describer as between 15 m (50 ft) and 16.5 m (54.1 ft) long, with a weight of up to 23 metric tons (25 tons); Prieto-Márquez et al. provided a smaller estimate of around 12.5 metres (41 ft), still among the longest ornithischians and representing the largest known lambeosaurine.
Morris interpreted this species as water-bound, due to features like its size, its tall and narrow tail (interpreted as a swimming adaptation), and weak hip articulations, as well as a healed broken thigh bone that he thought would have been too much of a handicap for a terrestrial animal to have survived long enough to heal.