Prosaurolophus: a hadrosaurid with a low nasal crest

Prosaurolophus maximus was a large saurolophine hadrosaurid from the Late Cretaceous of western North America. It is less famous for an elaborate crest than for the number of skulls that let palaeontologists compare individuals. Ten articulated skulls from Alberta provide a rare basis for measuring anatomical variation and proposing a growth sequence. That sample also helps evaluate Prosaurolophus blackfeetensis, a name once separated largely by differences in the nasal crest.

Quick facts

From a museum skull to a larger sample

Barnum Brown named Prosaurolophus maximus in 1916 from a skull collected in Alberta in 1915. The holotype, AMNH 5836, preserves a nearly complete skull and lower jaws. Its damaged snout affected early restorations, and later, less distorted skulls helped refine the outline. Further fossils from the Dinosaur Park Formation of Alberta and the Two Medicine Formation of Montana made it possible to compare individuals rather than build a portrait from one type specimen.

The genus name means ‘before Saurolophus’, a historical comparison with a taller, backward-pointing crest in another hadrosaurid. The name does not establish an ancestor-descendant relationship. Prosaurolophus and Saurolophus are related saurolophines, but a resemblance in one skull feature is not a direct record of one genus evolving into the other.

A crest measured across growth

McGarrity, Campione and Evans described cranial anatomy from ten articulated skulls and quantified their variation. The specimens span a range of sizes and support a hypothesised ontogenetic series. As the skull grew, its proportions changed; the low nasal crest remained a recognisable structure but did not become the tall tube or blade seen in some popular images of other hadrosaurids.

The same sample matters for the name Prosaurolophus blackfeetensis. That form had been distinguished from geologically younger Montana material partly by crest shape. When the authors compared the Montana features with the variation in the Alberta sample, they found no robust separation in their measurements or phylogenetic character matrix. They treated P. blackfeetensis as a junior synonym of P. maximus, extending the known range of the species rather than maintaining two species on an overlapping crest pattern.

What the skull can and cannot say

A bony crest is direct evidence; a fleshy extension over it is not. The shape of the nasal bones has prompted proposals for a soft-tissue swelling, but no preserved structure establishes its outline, colour or display role. Hadrosaurid crests could have been involved in visual recognition or sound production, yet those functions must be tested from anatomy and comparative evidence rather than inferred from an attractive reconstruction.

The skull and teeth support a plant-eating animal with the broad beak and dental batteries typical of hadrosaurids. The dental system replaced worn teeth and processed tough vegetation. Fossils from the same formations provide environmental context, but they do not show which plants one Prosaurolophus ate or which other animal it encountered. No particular herd structure or feeding height is demonstrated by the skull series.

Skin impressions preserve scales, not colour

Two juvenile specimens from Alberta preserve patches of skin impressions on parts of the body. Recent analysis of epidermal scales describes variation in scale size and shape across different body regions. Such patches show that the skin was not a uniform featureless surface. They do not preserve pigment well enough to recover a colour pattern, and an impression from one patch should not be extended across the entire animal without qualification.

The preserved skin also belongs to young individuals. It can inform a careful reconstruction of local texture, but it does not establish how adult skin looked or whether display features changed as the animal matured. Adult body colour remains unknown, and common brown, green or striped illustrations are artistic choices.

A hadrosaurid of river plains

Prosaurolophus lived during the Late Campanian in ecosystems represented by Alberta and Montana fossil localities. The Dinosaur Park Formation records low-relief river channels and floodplains that changed through time; marine influence varied as the Western Interior Seaway shifted. The formation is a geological package, not one frozen landscape occupied by every fossil species simultaneously.

Its body proportions are reconstructed from skulls and associated skeletal material, with adult length commonly placed around 7.5–8.5 metres. Mass values vary with the model and should be treated more cautiously. The genus is a strong example of how a sizeable sample can clarify age and variation while leaving behaviour and soft tissues open. Compare it with other ornithopods in the dinosaur catalogue, where apparent differences can be checked against the number and age of known specimens.