Stegoceras: The Small Pachycephalosaurid Dinosaur

In the grand tapestry of prehistoric life, the Stegoceras holds a unique place. This small dinosaur belonged to the Pachycephalosauridae family and roamed the Earth during the Late Cretaceous period. It left behind a rich fossil record that continues to intrigue paleontologists today. With its distinctive dome-shaped skull and agile bipedal stance, this dinosaur offers a fascinating glimpse into a world long past.

The name Stegoceras translates to ‘roofed horn’, a fitting moniker for a creature whose most distinctive feature was its thick, domed skull. Scientists believe that this skull was used in intra-species combat like modern-day rams. Despite its small size, this was a creature of remarkable resilience and adaptability with traits that allowed it to thrive in a world dominated by much larger predators.

Stegoceras Key Facts

Stegoceras pronunciationsteh-go-SER-as
Meaning of nameRoofed horn
Type SpeciesStegoceras validum
When it Lived83.5 to 66.0 MYA
PeriodLate Cretaceous
EpochLate/Upper Campanian to Late/Upper Maastrichtian
Length7.9 ft
Height2.3 ft
Weight0.04 tons
MobilityMoved on two legs
First Discovery1898 by Lawrence Lambe
Location of first findAlberta, Canada
First Described by1902 by Lawrence Lambe
HolotypeCMN 515 and CMN 1423

Stegoceras Origins, Taxonomy and Timeline

Stegoceras is a fascinating dinosaur from the Late Cretaceous. Explore its origins, key facts, discovery, and its role in the prehistoric ecosystem.

The Stegoceras, or ‘roofed horn’, derives its name from the Greek words ‘stegos’ meaning roof and ‘keras’ meaning horn. This name is a nod to the dinosaur’s most distinctive feature–its thick, domed skull, which scientists believe was used in intra-species combat. 

This dinosaur is a member of the Pachycephalosauridae family, a group of herbivorous dinosaurs known for their domed skulls. The type species is Stegoceras validum, first described by Lawrence Lambe in 1902.

This herbivore lived during the Late Cretaceous period from the Late/Upper Campanian to the Late/Upper Maastrichtian. This was a time of significant change as the Earth’s continents slowly take on their modern forms and new types of flora and fauna emerge.

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Discovery & Fossil Evidence

The first fossil was discovered in 1898 by paleontologist Lawrence Lambe in Alberta, Canada. This initial find was a partial skull but it was enough to identify the Stegoceras as a new species. Since then, additional fossils have been found in other regions of Canada as well as in the United States, specifically in Montana and New Mexico. These finds have helped to expand our understanding of this unique dinosaur and its place in the prehistoric world.

Stegoceras skeleton
Sebastian Bergmann from Siegburg, Germany, CC BY-SA 2.0, via Wikimedia Commons

The fossil record is quite extensive, with numerous skulls and partial skeletons having been unearthed over the years. The quality of these fossils varies. Some have been nearly complete and others consist of only fragments. However, even the most fragmentary fossils provide valuable insights into its anatomy and lifestyle.

Two of the most notable specimens, discovered by Lambe, consist of a nearly complete skull and partial postcranial skeleton. They have played a crucial role in defining the Stegoceras as a species and continue to be a subject of study for paleontologists.

Stegoceras Size and Description

This was a small dinosaur but what it lacked in size, it made up for in its unique physical characteristics. Its most distinctive feature was its thick, domed skull, which was likely used in intra-species combat. But there’s more to this dinosaur than just its skull. Let’s delve deeper into its physical description and size.

Short description of Stegoceras

It was a bipedal dinosaur, meaning it moved on two legs. Its body was compact with a short neck and tail. The head was large in proportion to the body and had a thick, domed skull. This dome was made of solid bone and could have been as much as 7.5 cm thick in some individuals. The dinosaur’s skin is not well known but it was likely similar to that of other dinosaurs and covered in scales.

Size and Weight of Type Species

Stegoceras size
Steveoc 86, CC BY-SA 4.0, via Wikimedia Commons

The Stegoceras was a small dinosaur with an estimated length of about 2.4 meters. As for its weight, estimates are not readily available. Given its size, it was likely relatively lightweight. It’s important to note that these are estimates and actual sizes could have varied among individuals. As with all dinosaurs, our understanding of its size and weight is based on the fossil record, which–while extensive–is still incomplete.

The Stegoceras in Detail

This was a creature of remarkable adaptability. Its thick, domed skull was not just a defensive tool, but also a symbol of its resilience. This skull was made of solid bone and likely used in intra-species combat like modern-day rams. The fact that the Stegoceras could withstand such impacts speaks to its toughness and adaptability.

One of the most notable specimens is the holotype, designated as CMN 1423. This specimen, consisting of a nearly complete skull and partial postcranial skeleton, has provided invaluable insights into the Stegoceras’s anatomy and lifestyle. It has helped to define this species and continues to be a subject of study for paleontologists.

Its small size and bipedal stance allowed it to navigate its environment with agility. This, combined with its herbivorous diet, suggests that the Stegoceras was a creature well-adapted to its environment and capable of surviving and thriving in a world dominated by much larger predators.

The Stegoceras in its Natural Habitat

In the Late Cretaceous period, this dinosaur found its home in a world vastly different from our own. North America was split by an interior seaway, forming two paleocontinents–Laramidia and Appalachia. The Stegoceras once roamed the more western of these two paleocontinents, Laramidia. This landscape was a lush, verdant expanse that was teeming with life and echoing with the calls of creatures that have long since vanished from the earth. The climate was warm and humid. This tropical paradise fostered the growth of a diverse array of flora. The compact size and agile form of the Stegoceras was well-suited to navigate through the dense vegetation, using its keen senses to forage for food and evade predators.

As an herbivore, it lived primarily on a diet of plants. Its beak-like mouth was perfect for plucking leaves and fruits from the abundant vegetation. Its bipedal gait allowed it to move swiftly and nimbly and was a key factor in its survival. It could dart through the underbrush to evade larger predators and swiftly reach its food sources. This was likely a solitary creature, its small size and agile nature lending itself more to a solitary lifestyle than a herd mentality.

It’s possible that its unique skull features played a role in the dinosaur’s social interactions, perhaps used in head-butting contests to establish dominance or attract mates. Despite its small size, this was a resilient and adaptable creature that showcased the incredible diversity and adaptability of life during the age of dinosaurs.

Interesting Points about Stegoceras

  1. This is one of the best-known pachycephalosaurs, a group of dinosaurs known for their distinctive dome-shaped skulls.
  2. The name means “roofed horn” in reference to the thick, bony dome on its head.
  3. The dinosaur’s dome-shaped skull was likely used in head-butting contests, similar to modern-day rams.
  4. It was a small dinosaur but its agile form and swift locomotion made it a resilient survivor in its environment.
  5. Despite its small size, it had a relatively large brain for a dinosaur. This suggests it may have been more intelligent than some of its contemporaries.

Contemporary Dinosaurs

In the vast expanse of prehistoric time, the Stegoceras shared its existence with an intriguing array of contemporary Laramidian dinosaurs. Among these were the Hanssuesia, Sphaerotholus, and Saurolophus, each contributing to the intricate dynamics of their shared environment.

The Hanssuesia was smaller in stature and might have been an agile participant in this ancient world. Its interactions with the Stegoceras as a fellow pachycephalosaurid could have been a fascinating dance of coexistence–perhaps a delicate balance between competition and indifference. The Sphaerotholus was another contemporary pachycephalosaurid that might have presented an interesting contrast to the Stegoceras. Their encounters were possibly marked by displays of dominance or avoidance and would have added another layer to the complex relationships within their shared habitat.

The Saurolophus, considerably larger than the Stegoceras, presents a different dynamic. This herbivore, with its distinctive crest, might have grazed alongside our main dinosaur. Their lives may have intertwined not by competition, but by a shared need for the lush vegetation of their environment. The Stegoceras, Hanssuesia, Sphaerotholus, and Saurolophus together paint a vivid picture of life in a time long past.

List of All Dinosaurs

We have created a list of all dinosaurs we have covered here, sorted across the seven main groups of dinosaurs. We also include information about their type of diet, (omnivore, herbivore or carnivore) and the time they lived.

Frequently Asked Questions

What did this dinosaur eat? 

It was an herbivore, subsisting primarily on a diet of plants.

How did it move?

The Stegoceras moved on two legs, using its swift and agile locomotion to navigate through its environment.

What was the purpose of the dome-shaped skull?

Its dome-shaped skull was likely used in head-butting contests, similar to modern-day rams.

Was this a solitary or herd animal? 

It was likely a solitary creature, its small size and agile nature lending itself more to a solitary lifestyle than a herd mentality.

How big was this dinosaur?

This was a small dinosaur, with adults reaching lengths of up to 2.4 meters.


Please note that the information in this article is based on various sources, drawing on scientific research, fossil evidence, and expert analysis. We aim to provide a comprehensive and accurate overview of the Stegoceras. However, but please be aware that our understanding of dinosaurs and their world is constantly evolving as new discoveries are made.

Article last fact checked: Joey Arboleda,06-14-2023

Featured Image Credit: Michael B. H., CC BY-SA 4.0, via Wikimedia Commons