Euoplocephalus: The Well-Armored Dinosaur of the Late Cretaceous Period

In the vast and diverse world of dinosaurs, the Euoplocephalus holds a unique place. This ankylosaurid dinosaur, whose name means ‘well-armored head’, roamed the earth during the Late Cretaceous period. Its distinctive features and fascinating history make it a subject of great interest for paleontologists and dinosaur enthusiasts alike.

The Euoplocephalus is a testament to the incredible diversity and adaptability of life on Earth millions of years ago. Its well-armored body and club-like tail are a testament to the survival instincts that allowed it to thrive in a world filled with predators. This dinosaur’s story is not just about its own life, but also about the world it lived in and the changes that have occurred since then.

Key Facts

Euoplocephalus pronunciationyoo-OP-loh-SEF-ə-ləs
Meaning of nameWell-armored head
Type SpeciesStereocephalus tutus
When it Lived83.5 to 66.0 MYA
PeriodLate Cretaceous
EpochLate/Upper Campanian to Early/Lower Maastrichtian
Length23.0 ft
Height5.9 ft
Weight2.0 tons
MobilityMoved on all four legs
First Discovery1897 by Lawrence Lambe
Location of first findAlberta, Canada
First Described by1910 by Lawrence Lambe
HolotypeNMC 1308

Euoplocephalus Origins, Taxonomy and Timeline

Euoplocephalus is a fascinating dinosaur from the Late Cretaceous period. Discover its key facts, origins, discovery history, and unique features that set it apart.

The Euoplocephalus has a name which means ‘well-armored head’. This name is derived from the Greek words ‘eu’ meaning true, ‘hoplo’ meaning armored, and ‘kephale’ meaning head. It was originally given the named Stereocephalus but was later changed as the name had already been given to a genus of beetle.

This dinosaur is a member of the Ankylosauridae family, which is part of the larger group of dinosaurs known as Thyreophora, or ‘shield bearers’. This group also includes the famous Stegosaurus. It is part of the Ankylosaurinae subfamily, and its closest relatives include Ankylosaurus and Pinacosaurus. The genus contains only one species, the type species Euoplocephalus tutus. 

It lived during the Late Cretaceous period, specifically in the Late/Upper Campanian to Early/Lower Maastrichtian. This was a time of significant change on Earth, with the continents moving towards their current positions and the climate becoming cooler and drier. The Late Cretaceous was also the last period of the Mesozoic Era, often referred to as the ‘Age of Dinosaurs’.

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Discovery & Fossil Evidence

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

The first fossils of the Euoplocephalus were discovered in 1897 by Lawrence Lambe in Alberta, Canada. These fossils included a partial skull and some postcranial remains. Other ankylosaurid remains were initially thought to belong to this dinosaur, but they were later sorted out. Since its discovery, numerous other fossils have been found in both Canada and the United States. These fossils have provided evidence that prove this creature was an herbivore and a formidable creature with its body covered in bony spikes and armor plating. Its tail, equipped with a bony club, served as a powerful defensive weapon. 

Euoplocephalus Size and Description

This member of the Ankylosauridae family was a dinosaur that was as fascinating as it was formidable. Its body was covered in bony armor and it had a distinctive club-like tail. But what did this dinosaur really look like, and how big was it? Let’s delve into the details.

Short description of Euoplocephalus

This was a quadrupedal dinosaur, meaning it moved on all four legs. Its body was low and broad–a shape well-suited for its herbivorous diet. The head was small compared to its body but it was well protected by bony plates. Its neck was short and muscular in order to support the weight of its heavy head.

The vertebrae were also unique, with additional ossifications providing extra support and protection. Its limbs were robust and designed to carry its heavy body. The tail of the Euoplocephalus was its most distinctive feature. It was long and ended in a club-like structure, which was likely used as a defensive weapon.

Size and Weight of Type Species

Euoplocephalus size
Matthew Martyniuk, CC BY 3.0, via Wikimedia Commons

This was a medium-sized dinosaur. Based on current knowledge paleontologist believe it measured about 23 feet in length, stood 5.9 feet tall and weighed around 2 tons. This size made it one of the largest members of the Ankylosauridae family.

However, it’s important to note that these are estimates, and the actual size could have varied. Some specimens may have been smaller or larger than the average. Despite these variations, this was undoubtedly a formidable creature; its size only added to its defensive capabilities.

The Dinosaur in Detail

The Euoplocephalus was not just another dinosaur. Its body was a fortress and its armor a shield against predators. Every aspect of its design was geared towards survival.

One of the most distinctive features of the Euoplocephalus was its armor. Bony plates, known as osteoderms, covered its body in order to provide protection against predators. These plates varied in size and shape, creating a mosaic of armor across its back, flanks, and tail. Some of these plates even had spikes that added an extra layer of defense.

The tail of the Euoplocephalus was another marvel of design. It ended in a club-like structure, made of two large osteoderms. This tail club was likely used as a defensive weapon, swung at predators to inflict damage. The tail club of the Euoplocephalus is one of the best-known examples of a weaponized tail in the dinosaur world.

The Euoplocephalus in its Natural Habitat

This herbivorous dinosaur lived during the Late Cretaceous period during a time when the continents were moving towards their current positions and the climate was becoming cooler and drier. This dinosaur would have inhabited areas that were rich in vegetation, providing ample food for its herbivorous diet. The Euoplocephalus made its home on Laramidia–the western half of what is now known as North America.

The environment of the Euoplocephalus would have been diverse, with a range of different plants and animals. As an herbivore, it would have relied heavily on vegetation for sustenance. It’s likely that it fed on low-lying plants by using its toothless beak to strip leaves and its cheek teeth to grind down the plant material.

This dinosaur was a quadruped, moving on all four legs. This mode of locomotion suggests that it was a slow-moving creature like most armored dinosaurs. Despite its slow speed, it was well-equipped to defend itself against predators. Its body armor and tail club would have been formidable deterrents to any potential threats.

Its social behavior is a subject of speculation. Some paleontologists suggest that it may have traveled in herds, providing additional protection against predators. If this was the case, this dinosaur would have played a significant role in shaping the landscape around it, as large herds of herbivores can have a significant impact on the vegetation.

Interesting Points about Euoplocephalus

  1. It was one of the most heavily armored dinosaurs. Its body was covered in bony plates and spikes, providing excellent defense against predators.
  2. Its tail club was a powerful weapon. Swung with great force it would likely inflict damage to any would be predator.
  3. Despite its formidable defenses, it was an herbivore and it had a voracious appetite. Heavy, armored bodies require a lot of food and energy.
  4. It had an impressive defense mechanism. Its tail was equipped with spikes and could be swung like a club, providing a powerful deterrent to any predator that dared to approach. 
  5. It may have also been a social creature. Some paleontologists speculate that it may have traveled in herds. This social behavior could have provided additional protection against predators, as there is safety in numbers.

Contemporary Dinosaurs

The Euoplocephalus shared its existence with a captivating ensemble of contemporaries. These fellow dinosaurs were each unique in their own right, their lives intertwined in the rich narrative of evolution.

Imagine, if you will, a world where the Euoplocephalus roamed alongside the Anodontosaurus, an ankylosaurid that was considerably smaller. This smaller contemporary, while not as physically imposing, had its own set of survival strategies that allowed it to thrive in the same environment. 

Closely related to these two ankylosaurids was the Dyoplosaurus. It was larger than the Euoplocephalus, and this size difference might have influenced their interactions. The Dyoplosaurus could have been a competitor, a threat, or perhaps even an indifferent cohabitant, its size allowing it to access resources that the Euoplocephalus could not.

A third ankylosaurid could be spotted alongside its relatives–the Scolosaurus.  Its smaller size might have allowed it to occupy ecological niches that were inaccessible to the larger Euoplocephalus, illustrating the diverse strategies these dinosaurs employed to survive in the same environment.

Lastly, the Edmontonia–a nodosaurid ankylosaur–was roughly the same size as the Euoplocephalus. These two might have had fascinating interactions, perhaps competing for the same resources or even acknowledging each other as equals. Through this exploration of closely related and similarly adapted dinosaurs, we gain a deeper understanding of the Euoplocephalus’s life and the intricate ecosystem it was part of.

Frequently Asked Questions

What does the name mean?

The name means ‘well-armored head’, a fitting description for this heavily armored dinosaur.

What did this dinosaur eat?

It was an herbivore. It likely fed on a variety of plants including conifers, seed ferns, and gingkos.

How did it defend itself?

The Euoplocephalus had a body covered in bony armor and a tail equipped with a club-like structure. These features would have provided excellent defense against predators.

How big was this dinosaur?

This was a medium-sized dinosaur. It measured about 23 feet in length and weighed around 2 tons.

Did it move on two legs or four?

It was a quadruped, meaning it moved on all four legs.


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 Euoplocephalus. However, 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, 06-11-2023