An Ultimate Guide to Pachyrhinosaurus: Thick-Nosed Lizard

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Name MeaningThick-nosed lizardHeight3-3.5 meters (10-11.5 feet)
PronunciationPah-kih-rye-no-SAWR-uhsLength6–8 meters (20–26 feet)
EraMesozoicLate CretaceousWeight3–3.6 tons (6,600–7,900 lbs)
ClassificationDinosauria, Ornithischia & CeratopsiaLocationChina (Asia)

Pachyrhinosaurus Pictures

Pachyrhinosaurus dinosaur roaring 3D render - elenarts108 via Istock
Pachyrhinosaurus dinosaur roaring 3D render – elenarts108 via Istock

The Pachyrhinosaurus

Gage Beasley Prehistoric's Pachyrhinosaurus Concept
Gage Beasley Prehistoric’s Pachyrhinosaurus Concept

Pachyrhinosaurus is a genus of herbivorous dinosaurs that lived during the Late Cretaceous Period, approximately 70 to 68 million years ago. 

It was a member of the Ceratopsidae family, a group of herbivorous dinosaurs that lived in Western North America during the Late Cretaceous Period and are known for their elaborate neck frills and head adornments. 

The most famous member of this family is the Triceratops, and the Pachyrhinosaurus is distantly related to this massive dinosaur. 

First discovered in 1946, Pachyrhinosaurus was unlike other members of the ceratopsid family in appearance. 

The most obvious difference is the absence of prominent horns on its nose like those of its relatives. 

Pachyrhinosaurus | Elenarts108 via Getty Images

Instead, the Pachyrhinosaurus had a lumpy mass of bone on its face, earning it the “thick-nosed lizard” name.

Pachyrhinosaurus is known from more than a dozen partial skull fossils and several other bone fragments discovered in various locations across Canada. 

At least three species have been identified in the genus, and scientists have learned many interesting details about this dinosaur over the years. 

In this article, we’ll discuss some of the most interesting facts about the Pachyrhinosaurus based on available evidence. 

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

Physical Characteristics

In addition to the similarities in their name, the Pachyrhinosaurus is also about the same size as a modern rhinoceros. 

Pachyrhinosaurus was a relatively large dinosaur but small compared to other ceratopsians. 

On average, the largest species of this dinosaur (P. canadensis) measured around six to eight meters (20 to 26 feet) in length and stood at a height of approximately three meters (10 feet). 

Gage Beasley Prehistoric's Pachyrhinosaurus Concept
Gage Beasley Prehistoric’s Pachyrhinosaurus Size Comparison Chart

Weight estimates for P. canadensis range between 3 and 3.6 tons on average. 

The other two species of this dinosaur, P. lakustai and P. perotorum, were smaller, with an estimated length of about five meters (16.4 feet) and a mass of approximately two tons. 

Pachyrhinosaurus had a robust and stocky build. 

Its barrel-shaped torso was supported by four strong legs. 

It also had a relatively short, muscular tail.

Pachyrhinosaurus | Elenarts108 via Getty Images

As with other ceratopsians, the most distinctive feature of Pachyrhinosaurus was its large head and prominent bony frills. 

The frill at the back of its skull was relatively short and wide compared to other ceratopsians.  

This dinosaur did not have the long and elaborate horns seen in most of its relatives. 

Instead of long horns, ‬Pachyrhinosaurus had a large bony mass on its nose. 

The lumpy mass of bone, also called a boss shield or boss, looked like an enormous tree stump on top of the dinosaur’s snout. 

P. canadensis skull cast, Geological Museum, Copenhagen | FunkMonk via Wikipedia (CC BY-SA 3.0)

A second, smaller boss was also located above the Pachyrhinosaurus’ eyes. 

Some species of Pachyrhinosaurus had two small, backward-pointing horns around the edges of their frill. 

The different Pachyrhinosaurus species also had various ornaments on their nasal boss, which helped to distinguish them. 

Scientists are still studying the boss shield and other adornments on the Pachyrhinosaurus’ face to better understand their function. 

However, they were most likely used for competition between males, defense against predators, or simply for species recognition. 

Habitat and Distribution

Pachyrhinosaurus lived during the Late Cretaceous Period in parts of what is now North America. 

The geographic range of this dinosaur covered different regions of present-day Alberta, Canada, Alaska, and the Western United States. 

Fossils of Pachyrhinosaurus discovered so far have been from these areas.

During the Late Cretaceous, the environment where Pachyrhinosaurus lived bordered the ancient Western Interior seaway, which covered most of North America. 

Due to changing sea levels, the region was an offshore and near-shore marine habitat characterized by tidal flats, peat swamps, river channels, and floodplains. 

River Channels | shaunl via Getty Images

The specific habitat of this dinosaur was bounded by a vast mountain range to the west.  

The Late Cretaceous climate in North America was generally warm, with global temperatures higher than it is today. 

The region where the Pachyrhinosaurus lived was warm and humid with a temperate to subtropical climate.

The dinosaur lived in diverse environments that ranged from coastal plains to inland forested regions populated by tropical plants that served as an abundant food source for this dinosaur and other Late Cretaceous herbivores. 

Behavior and Diet

A herd of P. perotorum resting next to contemporaneous paleofauna from the Prince Creek Formation | Andrey Atuchin via Plos One (CC BY 4.0)

Pachyrhinosaurus was a medium-sized, quadrupedal dinosaur. 

The dinosaur had sturdy limbs and broad feet that were strong enough to support its massive frame. 

Although it was primarily terrestrial, evidence suggests they showed semi-aquatic adaptations and may have been capable of swimming or wading in shallow water. 

Pachyrhinosaurus was one of the few ceratopsian dinosaurs with confirmed evidence of group or social behavior. 

Fossil evidence suggests that this dinosaur lived in herds or groups consisting of individuals of different ages and sizes.

In one instance, fossils of numerous individuals that appeared to have been killed in a flood were found together. 

Restoration of P. lakustai | Nobu Tamura via Spinops

As with other herding animals, Pachyrhinosaurus likely used visual displays for intraspecific communication.

Differences in the size and structure of their facial features most likely helped establish dominance within the herd and attract mates. 

Pachyrhinosaurus individuals moved around in groups like this in search of food. 

They were grazing herbivores with strong cheek teeth adapted to chewing tough fibrous plant materials. 

This dinosaur likely fed on a variety of plant materials, such as ferns, conifers, and cycads, that were abundant in their home habitat. Its beak-like mouth was effective for plucking and biting vegetation.

Life Cycle

Pachyrhinosaurus was a ceratopsian herbivorous dinosaur that lived in the Cretaceous Period of Alberta, Canada. | CoreyFord via Getty Images

Pachyrhinosaurus reproduced sexually, with males and females coming together to mate during specific seasons of the year. 

Male Pachyrhinosaurus most likely engaged in elaborate displays and competition for mates. 

Mating behavior in horned ceratopsians most likely involved locking while pushing and twisting opponents.

The flattened boss of the Pachyrhinosaurus means they pushed or rammed each other instead of locking horns like their other relatives. 

Pachyrhinosaurus would have laid eggs after mating. 

It is believed that they constructed nests on the ground, potentially in protected areas such as dense vegetation. 

Model of Protoceratops hatchlings based on the Oviraptor nest AMNH 6508. This nest was originally thought to represent Protoceratops eggs | Ballista via Wikipedia (CC BY-SA 3.0)

Fossilized nests attributed to related ceratopsians have been found.

This indicates that the Pachyrhinosaurus probably cared for their eggs to some extent.

Newly hatched juveniles also remained with the herds, protected by their parents. 

Juvenile Pachyrhinosaurus individuals developed rapidly within the first few years of their life. 

They attained about 28% of their adult body size by the time they were one year old and were almost half the adult size by age two. 

After reaching maturity, the growth rate slowed down significantly. 

Pachyrhinosaurus | Elenarts108 via Getty Images

Members of this genus reached their maximum adult size at about 20 years of age. 

The presence of distinct growth banding in the bones of this dinosaur suggests that their growth was seasonal. 

They grew faster during periods of abundance and slowed down during harsh conditions. 

Juvenile forms of this dinosaur looked like their parents but lacked pronounced nasal bosses, horns, and other facial features. 

They only developed these attributes associated with sexual selection after reaching maturity.

Evolution and History

Pachyrhinosaurus was a ceratopsian herbivorous dinosaur that lived in the Cretaceous Period of Alberta, Canada. | CoreyFord via Getty Images

Pachyrhinosaurus was a centrosaurine ceratopsid. 

This means it belongs to the Centrosaurinae subfamily and is closely related to dinosaurs like Centrosaurus and Styracosaurus.

The earliest members of this family can be traced back to the Early Cretaceous Period, approximately 100 million years ago. 

Early ceratopsids, such as Psittacosaurus, were small bipedal dinosaurs that lacked the prominent horns and frills seen in later species. 

Over time, ceratopsids diversified significantly, and different genera and species with various horn and frill configurations appeared.

Skull differences between different growth stages of P. perotorum | Anthony R. Fiorillo, Ronald S. Tykoski via Plos One

Pachyrhinosaurus is known from Late Cretaceous North America, roughly 70 to 68 million years ago. 

The dinosaur represents a unique branch of ceratopsid evolution characterized by the absence of prominent nasal horns.

Their horns were replaced by bony mass on the snout and brows. 

However, the nasal boss still served a similar purpose as the horns of other ceratopsians, which is for display and intra-species combat.

Scientists have identified possible transitional species between the older horned ceratopsids like Styracosaurus and younger ones like Pachyrhinosaurus

Pachyrhinosaurus was a Ceratopsian herbivorous beaked dinosaur that lived in Alberta, Canada during the Cretaceous Period. | CoreyFord via Getty Images

Einiosaurus and Achelousaurus are two ceratopsid genera whose nasal horns appear to be anatomically transitional. 

Their nose horns were shorter and had a sharp, downward orientation. 

Experts think the nasal horns of the ceratopsids continued to change this way until the emergence of species like the Pachyrhinosaurus with practically no horns at all. 

The genus emerged in Montana but gradually moved northwards into Alberta and Alaska. 

The different species within the genus also show remarkable variations in their facial structures. 

Interactions With Other Species

Restoration of a confrontation between P. canadensis and Albertosaurus | ABelov2014 via Deviant Art

As a large herbivore, Pachyrhinosaurus was probably a prime target for a variety of predators present in Late Cretaceous North America, such as Albertosaurus and Daspletosaurus

These tyrannosaurids (relatives of the T. rex) were the apex predators in the region of North America where this dinosaur lived. 

The massive size of this dinosaur and their herding behavior would have provided some level of protection from predators, but juveniles and weak individuals would have been prone to predator attacks. 

In terms of competition, numerous other herbivorous dinosaurs share the same habitat and geographic range as the Pachyrhinosaurus

Pachyrhinosaurus | CoreyFord via Getty Images

Hadrosaurs were the most abundant group in this region, but various ornithomimids, ankylosaurids, and ornithopods were present as well. 

These herbivores would have competed with the Pachyrhinosaurus for food and other resources. 

Although niche partitioning probably allowed the coexistence of these different herbivorous species, occasional encounters between them cannot be ruled out. 

The different species of Pachyrhinosaurus also lived alongside each other and may have competed as well. 

Cultural Significance

P. lakustai skull | James St. John via Flickr

The fossil site where the first Pachyrhinosaurus fossils were found was discovered as far back as the 1880s. 

But they did not receive any attention until much later in the 20th century. 

Instead, horned relatives like the Triceratops stole the show, quickly becoming one of the most popular dinosaur species ever. 

The discovery of new Pachyrhinosaurus fossils in the 1950s, including more than a dozen partial skulls from the Alberta province alone, quickly boosted the popularity of the Pachyrhinosaurus among paleontologists and the general public. 

The discovery of a ceratopsian dinosaur that looked nothing like its famous relatives was undoubtedly an interesting find for paleontologists. 

Pachyrhinosaurus skeletal mount. On display at the Royal Tyrrell Museum, Alberta | Etemenanki3 via Wikipedia (CC BY-SA 4.0)

It’s safe to say that the Pachyrhinosaurus owes its popularity to its distinctive appearance, unlike any other known ceratopsids. 

Studying the fossils of Pachyrhinosaurus found so far has provided valuable insights into the evolution of the ceratopsians.

Pachyrhinosaurus also provides a wealth of information about the nature of social relationships among the ceratopsids. 

For instance, the flattened bosses of the Pachyrhinosaurus indicate a behavioral shift from locking horns in combat to ramming or pushing. 

Pachyrhinosaurus has also made it easier to understand the growth pattern of the ceratopsids. 

Pachyrhisaurus in Walking with Dinosaurs: The 3D Movie | Photo via Walking with Wikis

The abundance of fossils across the different age groups has made it easier for scientists to chart the likely growth pattern of individuals in this dinosaur group. 

Although it isn’t quite as popular as others like the Triceratops or Kosmoceratops, Pachyrhinosaurus is also fairly well-known to the general public.

The dinosaur has been featured on screen in documentaries like Walking with Dinosaurs: The 3D Movie, released in 2013, and the Jurassic Fight Club TV series aired on the History Channel. 

Cameos like these contribute to the rising star status of this dinosaur. 


Pachyrhinosaurus is a genus of extinct ceratopsid dinosaurs that lived in the northwestern region of North America approximately 71 million to 67 million years ago.

This dinosaur lived during the Late Cretaceous in various habitats near the shores of the Western Interior Seaway. 

Although it was a close relative of other ceratopsid dinosaurs like Styracosaurus and Centrosaurus, it looked slightly different from them. 

One of the main anatomical differences shown by this dinosaur was the absence of prominent skull horns.

Instead, it had a bony mass on its nose. 

The nasal boss still served a similar purpose as the horns of other ceratopsians.

The discovery of the Pachyrhinosaurus contributes to our understanding of the diversity within the ceratopsian family and in the prehistoric animals of the Cretaceous Period in general. 


Was Pachyrhinosaurus a dangerous dinosaur?

Pachyrhinosaurus was a herbivorous dinosaur and would not have been considered dangerous to other animals in its ecosystem. 

It did have a few defensive mechanisms, including its giant frills and nasal boss shield. 

How did Pachyrhinosaurus use its horns and frill?

Although the exact purpose of Pachyrhinosaurus’ horns and frill is still debated, they likely served as visual displays and for intraspecific interactions such as species recognition, attracting mates, and establishing dominance within its herd.

Who discovered Pachyrhinosaurus

The first official fossils of the Pachyrhinosaurus were discovered by Charles M. Sternberg in 1946. 


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