April 4, 2022 Scott Kraus

Prosaurolophus, the Duck-Billed Dinosaur

Prosaurolophus (Greek—before saurolophus), pronounced pro-SAWR-O-LO-FUS, was a terrestrial genus of hadrosaurid (known as the duck-billed dinosaurs due to similarity of their head to that of modern ducks) dinosaur that lived during the late Cretaceous Period.  It is most commonly characterized by its long, broad skull and a small crest present near the eyes, which rose up like spikes above each eye and faced back.  Prosaurolophus is the earliest known flat-crested hadrosaur.

Quick Facts

About Prosaurolophus

There are two type species of genus Prosaurolophus:  P. maximus and P. blackfeetensis.

Some paleontological evidence suggests that Prosaurolophus lived in groups during part of the year and exhibited social displays via such ornamental tactics as its bony facial crest, flanked by nasal diverticula that would flare via inflatable soft tissue sacs, or sound for effect.

What Did Prosaurolophus Look Like?

Prosaurolophus was a large herbivore known for its flattened head and long, flat beak, described as being like that of a duck.  The duck-billed Prosaurolophus was an ornithischian (beaked, herbivorous dinosaurs whose name hails from the Greek and means “of a bird’ and ‘hip joint’) with a stiff tail that walked on its two hind limbs primarily, but could move on all four. Original hypotheses were that Prosaurolophus had webbed feet, but recent findings have suggested that its feet could have had pads.  This type species had a large head that was in proportion to the whole of its body, including its large rib cage.

A major difference between the two is that P. maximus had a smaller head which remained so, while the head and crest of P. blackfeetensis grew, the crest moving towards the eyes during maturity.  The sides of the crest were scooped, or concave, and seem to have afforded some protection for the eyes.

What Did Prosaurolophus Eat?

Prosaurolophus was an herbivore and its bill, or beak, was designed specifically for eating various types of thick vegetation.  The skull of Prosaurolophus enabled an advanced grinding motion when processing food.  There has been much debate as to whether Hadrosaurs were grazers that ate grasses and low lying plants, or browsers that ate leaves from tree branches.  Their teeth and chewing style suggests they were grazers, and recently found fossilized droppings from the late Cretaceous period suggest that Prosaurolophus ate fungi and bark from decomposing wood.  Thousands of teeth contained in “dental batteries” of each jaw continuously replace teeth that are shed naturally, or are worn down due to continuous and vigorous grinding of plant material.   These dental batteries likely served as effective roughage grinding mechanisms.

This chewing style explains some studies done on scratch markings on teeth which show that the chewing style of Prosaurolophus was different from present-day animals. Instead of a moveable lower jaw, a special joint in-between the upper and lower half of the jaw allowed the Prosaurolophus to bite down and slide its teeth together, grinding and tearing the vegetation it ate.  This amounted to a mouthful of thousands of teeth suitable for grinding food before it was swallowed.  Even the rim of Prosaurolophus’ beak appears to have been covered by an even stiffer substance, used for clipping branches and leaves.  It is believed that Prosaurolophus would have fed from ground level to about 13 feet (4 meters) above ground.

How Did Prosaurolophus Move?

As a hadrosaurid, Prosaurolophus could have moved in both bipedal and quadrupedal fashion, and likely exhibited both styles of movement.  It’s likely that in its ability to switch between a bipedal and a quadrupedal stance, when moving casually and feeding, the Prosaurolophus would walk on all fours.   It is thought that when it needed to run from a predator, Prosaurolophus would do so on its hind legs, with its body hardly leaving a horizontal pose.  Prosaurolophus had stout, strong back legs.  Its forelimbs were lightly built in comparison and used mostly for grasping and pulling foliage.

Prosaurolophus moved about in a cathemeral fashion, experiencing its days and nights via short intervals of hunting and socializing. Rather than being considered diurnal or nocturnal, the cathemeral pattern of living has been recognized since 1979 and since had been widely attributed to various species.   Such factors as food availability, predation and variable temperature affect the living cycles of beings.

Where Did Prosaurolophus Live?

Prosaurolophus preferred to live near rivers or near small bodies of water.   Prosaurolophus likely nested in both upland and lowland areas.  It is thought that diet, competition and general conditions contributed to the nesting habits of Prosaurolophus (and other dinosaurs and animals).   Fossils have been found in the North American United States and in Canada as well.

The climate would have been warmer than that of Alberta today.  Conifers were probably dominant as canopy foliage.  Fern bushes, tree ferns and flowering plants filled the area.  The Dinosaur Park Formation that Prosaurolophus called home for at least some time is thought to have been a lowland setting of rivers and floodplains that eventually became swampy.  Over time, the area became affected by marine conditions as the Western Interior Seaway moved westward.

The Discovery of Prosaurolophus

In 1915, paleontologist Barnum Brown discovered the skull of a prehistoric dinosaur in Alberta, Canada at Red Deer River in the Upper Cretaceous Dinosaur Park Formation around 76-75 million years ago.  It was the first discovered flat-crested hadrosaur, and Brown named it after its resemblance to the Saurolophus that he had described in 1912.  The formation was named after the Dinosaur Provincial Park, a UNESCO World Heritage Site.

The Red Deer River of Alberta is a major tributary of the South Saskatchewan River and is part of a larger system which empties into Hudson Bay.  This river originates on the Canadian Rockies’ Eastern slopes. Since then, Prosaurolophus fossils and slight mummifications have been discovered in various parts of the North American continent, primarily in the far north-western area and near Alberta, Canada.  Prosaurolophus found remains have been primarily disarticulated.

Several fossilized remains of P. blackfeetensis were found in a preserved bone bed in the Two Medicine Formation, Glacier County, Montana.  The Two Medicine Formation is known for numerous dinosaur eggs finds, dinosaur nests and their young.  The climate of this formation much farther East appears to have a drier one.  Some of the dinosaurs from the formation have been speculated to show signs of drought related death.

P. blackfeetenis was classified by Jack Horner in 1992 based on a specimen preserved in the Museum of the Rockies.

The Mad-mouth Antics of Prosaurolophus

The beak and jaw structure of the Prosaurolophus has intrigued scientists and paleontologists for decades.  Many studies have been done on the chewing style and eating habits of Hadrosaurs in general, leading to the discovery of the uniquely flexible jaw (for utilization of the dental battery) joint that is not present in any modern day animals.  When the upper and lower jaws of Prosaurolophus articulated to the closed position, the movement enabled a unique shearing effect to the most fibrous and toughest plants.

Part of the importance of Prosaurolophus lays in future determinations relevant to the two type species P. maximus and P. blackfeetensis.  Since paleontologists have found these Prosaurolophus species on virtual opposite ends of a river spectrum, already some differences have come to light- such as the differences in cranial structure between the two typed species and acknowledge differences that would have existed between the two climates, one eastern and one western.