An Ultimate Guide to Chasmosaurus: The Opening Lizard

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Name MeaningChasm Lizard Height2.5-3 meters tall at the shoulder (8-10 feet)
Pronunciationkaz-moh-SAWR-uhsLength4-5 meters (14-16 feet)
EraMesozoicLate CretaceousWeight1.5–2 metric tons (2,200–5,000 pounds)
ClassificationDinosauria, Ornithiscia & CeratopsiaLocationNorth America

Chasmosaurus Pictures

Chasmosaurus was a herbivorous ceratopsian dinosaur that lived in North America during the Cretaceous period
Chasmosaurus was a herbivorous ceratopsian dinosaur that lived in North America during the Cretaceous period | CoreyFord via iStock

The Chasmosaurus

Gage Beasley Prehistoric's Chasmosaurus Concept
Gage Beasley Prehistoric’s Chasmosaurus Concept

Chasmosaurus was a large herbivorous dinosaur that lived in North America during the Late Cretaceous Period.

It was a ceratopsid dinosaur, a family of dinosaurs known for their large neck frills and long nasal and cranial horns. 

Chasmosaurus was a relative of the famous Triceratops

But unlike the elephant-sized Triceratops, this dinosaur was of average build. 

One notable difference between this dinosaur and other ceratopsid dinosaurs is the large opening in its frills. 

Although several other dinosaurs had this gap in their frill, it was larger in the Chasmosaurus

The dinosaur’s name, which means “opening lizard” or “hollow lizard,” is a reference to this opening. 

Chasmosaurus dinosaur portrait
Chasmosaurus dinosaur portrait | Robert Fabiani via GettyImages

At least two confirmed species have been identified in the Chasmosaurus genus. 

Fossils of both species were recovered from rocks of the Dinosaur Park Formation in Canada, where the first fossil of this dinosaur was found in In 1898. 

Today, the Dinosaur Park Formation is the only place where fossils of this dinosaur have been found. 

The Chasmosaurus was among the first ceratopsian dinosaurs ever discovered and one of the best-known members of the family. 

In this article, we’ll discuss some of the facts that we currently know about the Chasmosaurus and how it lived. 

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

Physical Characteristics

Illustration of Chasmosaurus dinosaur in a white background
Illustration of Chasmosaurus dinosaur in a white background | CoreyFord via iStock

Chasmosaurus was a relatively large dinosaur but was medium-sized compared to other ceratopsians. 

It was a large, bulky animal roughly the same size as an Indian rhinoceros. 

It had an estimated length of about 4.3 to 4.8 meters (14.1–15.7 feet) and stood at an average height of about six to eight feet (1.8 to 2.4 meters) tall at the hips.

As with other ceratopsian dinosaurs, the most distinctive feature of Chasmosaurus was its large frill. 

This bony shield-like structure extended from the back of the dinosaur’s head, raising the overall profile of its skull. 

The frill of the Chasmosaurus was relatively large and flat compared to that of other ceratopsids.

It also differed from others due to the two large openings (fenestrae) at its center.

Gage Beasley Prehistoric's Chasmosaurus Size Comparison Chart
Gage Beasley Prehistoric’s Chasmosaurus Size Comparison Chart

But this opening was not just an empty space. 

It had a covering of skin which helped to preserve the appearance of a solid frill. 

The covering of frill skin was highly vascularized, and scientists think it probably served display or thermoregulatory purposes. 

The Chasmosaurus may have flushed blood into this area of its frill to create vivid colors during mating rituals or simply for heat exchange with its surroundings to keep its internal temperatures down. 

Like its relatives, Chasmosaurus had three horns on its face. 

One small horn was on its nose, and two more on the brows.  

The two species in the Chasmosaurus genus differed in the shape of their frills and the size of their cranial horns. 

Digital coloring of chasmosaurus dinosaur
Digital coloring of chasmosaurus dinosaur | Nobu Tamura via Wikimedia Commons CCA 3.0

In C. belli, the rear end of the frill was V-shaped, while the sides were straight. 

But for C. russelli, the frill was a shallow “U” shape, and the sides were more convex than straight. 

Chasmosaurus was one of the few ceratopsian dinosaurs with its skin impressions preserved. 

The dinosaur’s body was covered by a mix of large and small scales, which formed an intricately designed hexagonal or pentagonal rosette. 

The large scales were about 55 millimeters in diameter, with a space of about five to ten centimeters between them. 

The evenly spaced rows of large scales were interspersed by smaller scales. 

Unfortunately, it’s impossible to determine the exact color of this dinosaur when it was alive based on these skin impressions. 

Habitat and Distribution

Chasmosaurus was alive during the Late Cretaceous Period, specifically between 83.5 and 70.6 million years ago. 

This dinosaur lived in an area that is now part of western North America

Fossils of this dinosaur have been recovered from Canada and the United States.

The distribution of its remains suggests that it lived in a range of environments across these regions, including floodplains, river valleys, and upland forests. 

Chasmosaurus was well-adapted to a terrestrial lifestyle and could thrive in any habitat with a balanced mix of vegetation, water sources, and open spaces for foraging. 

The region where the Chasmosaurus lived was on the western shore of an inland sea that divided North America into eastern and western landmasses during the Cretaceous Period. 

Chasmosaurus was relatively medium-sized for a ceratopsian
Chasmosaurus was relatively medium-sized for a ceratopsian | Roman Garcia Mora via GettyImages

The western landmass known as Larimidia was home to the Chasmosaurus, with a higher concentration on the east coast of this landmass. 

This vast shallow sea, known as the Western Interior Seaway, created coastal and inland habitats that provided a suitable habitat for the Chasmosaurus and other dinosaur species. 

The Late Cretaceous climate was generally warm and temperate, with higher average global temperatures compared to today due to high amounts of greenhouse gases in the atmosphere. 

The temperature and general conditions varied across the seasons, but extremely cold temperatures were less common.

Behavior and Diet

Chasmosaurus was a quadrupedal dinosaur, meaning it walked on all four legs.

This dinosaur had sturdy limbs and a robust body structure similar to present-day rhinos. 

Chasmosaurus dinosaur head
Chasmosaurus dinosaur head | Corey Ford via Getty Images

Based on this body structure, this dinosaur was probably a relatively slow-moving animal but was capable of galloping at high speeds when necessary. 

Chasmosaurus likely exhibited a range of social behaviors, including living in herds or groups. 

In some ceratopsian species, multiple individuals have been found in close proximity, which suggests that these herbivorous dinosaurs were probably herding animals. 

The elaborate frill and facial horns of Chasmosaurus likely played a role in communication and display within their herds or social groups.

These features could have been used to establish dominance within the group, attract mates, or intimidate rivals. 

Although no evidence of sexual dimorphism has been found for the Chasmosaurus, these cranial features probably looked different for males and females. 

Chasmosaurus alongside its offspring
Chasmosaurus alongside its offspring | CoreyFord via iStock

Chasmosaurus was a herbivore that grazed or browsed on low-lying plants such as ferns, cycads, and possibly conifers. 

It had longer snout and jaws compared to other ceratopsian dinosaurs, which suggests that this dinosaur had a more specialized diet compared to its relatives. 

Its toothless beak was well-suited for cropping and snipping plant material, while the rows of grinding teeth further back in its mouth would have aided in breaking down plant matter for digestion.

Life Cycle

Like other dinosaurs, Chasmosaurus reproduced sexually. 

Although the exact process of courtship and mating is unknown, scientists speculate that the distinctive frills of this dinosaur played a significant role in attracting mates.

They were probably capable of filling the vascularized layer of frill skin with blood to change its color. 

This dinosaur likely fed on low-lying plants, using its parrot-like beak to bite off vegetation
This dinosaur likely fed on low-lying plants, using its parrot-like beak to bite off vegetation | Steamblust via Jurassic World Evolution Wiki

After mating, Chasmosaurus laid eggs in nests made on the ground. 

Fossil evidence of nesting sites and eggs has been found in some ceratopsid species. 

Specific Chasmosaurus nests have not been identified so far.

However, scientists have found fossils of a well-preserved juvenile Chasmosaurus, which provides a lot of information about the parental care exhibited by this dinosaur. 

Chasmosaurus likely cared for its young, with the juveniles staying close to their parents until maturity. 

Juvenile Chasmosaurus looked very similar to their adult forms but were relatively smaller. 

Their limb proportions were similar to that of the adults, but the frill was smaller and narrower at the back compared to adults. 

Evolution and History

Juvenile of this herbivorous dinosaur that lived during late cretaceous period
Juvenile of this herbivorous dinosaur that lived during late cretaceous period | CoreyFord via iStock

Chasmosaurus was a member of the family Ceratopsidae

This group of horned, frilled dinosaurs thrived throughout the Cretaceous Period. 

The oldest ceratopsians are known to have emerged during the Early Cretaceous Period about 140 million years ago. 

These primitive ceratopsian dinosaurs, such as the Protoceratops, were without frills and horns and were also bipedal.

The horned and frilled ceratopsians only began to emerge during the Late Cretaceous Period. 

They lived mainly in western North America, where they evolved into different forms. 

The frill and horns of this herbivorous dinosaur served for mate attraction and defense against predators
The frill and horns of this herbivorous dinosaur served for mate attraction and defense against predators | Steamblust via Jurassic World Evolution Wiki

Within the ceratopsid family, Chasmosaurus is classified in the subfamily Chasmosaurinae. 

Members of this subfamily are known to have possessed larger frills and larger brow horns compared to other ceratopsids in the Centrosaurinae subfamily. 

Interactions With Other Species

The Late Cretaceous ecosystem of western North America, where the Chasmosaurus lived, was teeming with diverse terrestrial lifeforms. 

In addition to Chasmosaurus, the landscape of Larimidia was populated by other iconic dinosaur groups, including hadrosaurs (duck-billed dinosaurs), ankylosaurus, and pachycephalosaurs.

These were mainly herbivorous dinosaurs that may have competed with the Chasmosaurus for food and other resources. 

Niche partitioning would have limited competition between these different dinosaur groups, with the Chasmosaurus having a more specialized diet compared to other herbivores (and even other ceratopsians) in its habitat. 

Daspletosaurus confronts a family of Chasmosaurus
Daspletosaurus confronts a family of Chasmosaurus | Stocktrek Images via GettyImages

As a large herbivore, Chasmosaurus was probably the top prey species for the top carnivores in its ecosystem. 

This includes one of the most notorious North American predators, the Tyrannosaurus rex, which lived around the same period.  

The intimidating look of this dinosaur would have deterred smaller predators from attacking full-grown adults. 

But massive carnivores like the T. rex could take on this rhino-sized carnivore. 

Juveniles or weak individuals would have been vulnerable to predators, their only protection being the safety of their herds. 

Cultural Significance

The first Chasmosaurus remains were discovered in the early 20th century
The first Chasmosaurus remains were discovered in the early 20th century | Sebastian Bergmann via Wikipedia CC BY-SA 2.0

Chasmosaurus was one of the first ceratopsians to be discovered. 

It was identified in 1898 by famous paleontologist Lawrence M. Lambe and was described in full detail a few years later by Charles R. Sternberg. 

Like most dinosaurs discovered so early in the geologic record, the Chasmosaurus became quite complicated. 

Many newly identified ceratopsians were placed in the genus, leading to so many invalid species. 

It took the diligent work of various scientists to eventually clean up the genus and narrow the number of species down to two: Chasmosaurus belli and Chasmosaurus russelli.

Chasmosaurus and its relatives have played a significant role in advancing our understanding of prehistoric life, especially about life at the end of the Cretaceous. 

George F. Sternberg preparing the skull of Chasmosaurus
George F. Sternberg preparing the skull of chasmosaurus | Internet Archive Book Images via Wikipedia Public Domain

This dinosaur and several other Late Cretaceous species marked the culmination of a group of animals that once held the title of Earth’s most dominant inhabitants. 

Chasmosaurus was also among the first dinosaur remains discovered in North America. 

The discovery of these 19th-century dinosaurs fueled public interest in this fascinating group of animals and contributed to the growing field of paleontology.

Chasmosaurus, along with other close relatives like the Triceratops, has continued to capture the imagination of the general public. 

They have been represented in various forms of media, including movies, books, documentaries, museum exhibitions, and other resources for education and entertainment. 


Chasmosaurus was a ceratopsid dinosaur that lived in Canada during the Late Cretaceous Period. 

The dinosaur’s name, which means “opening lizard,” references the large opening in its ornament. 

This earth-shaped opening was covered by a layer of skin that was probably brightly colored and served the purpose of attracting mates. 

Chasmosaurus was a medium-sized ceratopsian that lends its name to an entire subfamily due to its distinctive appearance. 

This herding herbivore is one of the best-known ceratopsian dinosaurs, thanks to an abundance of fossil remains that provide sufficient information about this dinosaur and its closest relatives. 


What is the difference between a Triceratops and a Chasmosaurus?

The Triceratops was bigger than the Chasmosaurus

But arguably, the most notable difference between them is the nature of their head ornaments. 

The frills of the Chasmosaurus had a large opening in it. 

The brow horns of this dinosaur were also not as prominent as that of the Triceratops. 

Who named the Chasmosaurus

Paleontologist Charles Hazelius Sternberg named the Chasmosaurus in 1914. 

He had initially given the name Protorosaurus to the genus in 1913 but had to rename it after he discovered that another animal already took the name.


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Jerry Young is a self-proclaimed prehistoric animal nerd. He has been fascinated with these ancient creatures for as long as he can remember, and his passion for them continues to this day. With his extensive knowledge and love for prehistoric animals, he is the perfect fit for Gage Beasley Prehistoric.

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