Prosaurolophus maximus is currently the only species recognized in its genus. A previous genus member was Prosaurolophus blackfeetensis. This species was differentiated from P. maximus by a steeper and taller skull ridge (1). Further investigation has led paleontologists to conclude that the differences between P. maximus and P. blackfeetensis are too insignificant to support two different species. Therefore, P. blackfeetensis is now regarded as a synonym to P. maximus (2, 3).
Despite the similar names, there has been debate on the relatedness between Prosaurolophus maximus and the Saurolophus genus. Recent analysis of their evolutionary relationship suggests that these two genera are indeed closely related (4). However, the relationship between the Prosaurolophus-Saurolophus grouping and the rest of Hadrosauria is still a matter of some uncertainty. Some features suggest them as relatives to Gryposaurus while others align them more closely with Edmontosaurus (5).
Prosaurolophus maximus was a hadrosaur, a “duck-billed” dinosaur. It lived in the Late Cretaceous, approximately 75.5 to 71 million years ago. P. maximus was a large herbivorous dinosaur, 8.5 m long and weighing close to 3000 kg (1). It was a common dinosaur in its environment, a habitat that it shared with a variety of dinosaurs, such as Troodon and Centrosaurus (2).
P. maximus walked on its hind legs, though it could support itself on all four limbs while at rest or walking slowly. It also used its smaller forelimbs to help it feed, pulling down branches or grasping fruit (2). Unlike other hadrosaurs, P. maximus had only a small triangular crest. It could have used this crest for display purposes, possibly with inflated air sacs similar to those of an anole lizard (3).
Prosaurolophus maximus lived in the Late Cretaceous, approximately 75.5 to 71 million years ago. It was an herbivorous dinosaur, like all other “duck-billed” hadrosaurs. Fossils for this taxon have been found in Alberta, at Dinosaur Park. During the time when P. maximus was alive, the environment was a forested floodplain. It was a well-watered area and had a variety of coastal marshes and swamps. The winters were likely cool in this area (1).
This site is known for an amazingly diverse array of fossils. Plants found in this area include ferns, conifers, and gingko. There were many other dinosaurs sharing this environment with P. maximus, such as the horned and frilled ceratopsids Centrosaurus and Styracosaurus. There were ankylosaur species as well, like Euoplocephalus. Gorgosaurus and Daspletosaurus are theropod dinosaurs related to Tyrannosaurus rex and could have preyed upon P. maximus. Additionally, there were dromeosaurs, pachycephalosaurs, and other hadrosaur species. Many other animal groups are also represented at this site, such as lizards, turtles, crocodilians, and small early mammals. Though bountiful in diversity, this ecosystem was marked by periodic droughts, which could have caused mass mortality among its dinosaurian residents (2).
Fossils of Prosaurolophus maximus have been found in large groupings. This has been used to infer herding behavior for this dinosaur (1). Like many hadrosaurs, or “duck-billed” dinosaurs, P. maximus had a bony crest on the roof of its skull.It is possible that it could have used this crest for social display or signaling. While this crest is small on P. maximus compared to some of its flashier relatives, some paleontologists think that their crest may have been enhanced with air sacs that would swell out during display, similar to the dewlap of anole lizards (2).
Fossil evidence shows that P. maximus and its hadrosaurid relatives had good vision, with large eyes and sclerotic rings. Sclerotic rings are bones found in the eyes of some dinosaurs and are thought to help support the eye. P. maximus was probably diurnal, active during the day. It had good hearing as well, with a large eardrum and lagena, part of the internal anatomy of the ear. These acute senses would have allowed P. maximus to be receptive to auditory and visual signals that might be produced by their crest structures (3).
Prosaurolophus maximus was first discovered as a damaged skull near the Red Deer River in Alberta. It was later described by the famous Barnum Brown in 1916. The name Prosaurolophus refers to the previously discovered Saurolophus, which Brown had described several years earlier. The two dinosaurs were similar in appearance, though Saurolophus had a more distinctly spiked head crest (1). The original P. maximus skull had a damaged snout and was incorrectly reconstructed because of it, but a more complete skeleton was described by William Parks in 1924 (2). Now, up to twenty-five individuals have been found for this species, though these skeletons are in varying states of completion (3).
Prosaurolophus maximus was an herbivore and had many adaptations to support this lifestyle. Like other hadrosaurs, or “duck-billed” dinosaurs, P. maximus had a multitude of teeth lining its jaws. It had as many as 50 teeth per jaw with up to 250 replacement teeth below the top rows. If a tooth wore out, these replacement teeth could quickly be moved up to take their place (1). P. maximus was able to hold food in its mouth using a cheek-like structure and chew this food using grinding motions (2).The front of the snout of P. maximus was toothless, resembling a duck’s beak in shape. It used this tough bill to crop foliage (1).
Its arms ended in grasping fingers, which were used to assist in foraging and holding vegetation for consumption (1). Due to this range of adaptations, P. maximus was able to exploit a wide range of feeding heights. It could feed from the ground up to 4 m high, moving both bipedally (on just its hind legs) and quadrupedally, or on all four legs (2).
