Edmontonia

The Apex and Largest Species of Nodosauridae

Edmontonia belongs to the group known as “Nodosauridae” among the armored dinosaurs (Ankylosauria).
This group evolved differently from the famous Ankylosaurus (Ankylosauridae).

Ankylosauridae

Possessed a hammer (club) at the tip of the tail.

Nodosauridae

Did not possess a tail hammer, but instead developed large spikes on their shoulders and the sides of their bodies.

Edmontonia is the largest dinosaur in the Nodosauridae family and appeared in the most recent era.
In other words, it can be said to represent the final form of evolution for this group.

Iron-Clad Defense System: “Giant Spears” Glaring Forward

Top-Tier Super Armor and Forward-Facing Spikes

Edmontonia’s back was equipped with robust super armor (bony plates) described as being “like a heavy tank.”
However, its greatest feature was the sharp and massive spikes lined up like a breakwater on the sides of its shoulders.

Notably, these spikes faced “forward.”
While the spines of many armored dinosaurs faced sideways or backward, Edmontonia’s forward-oriented spikes were a powerful weapon with aggressive implications, not merely for defense.

Intimidation and Display

These developed spikes are thought to have been used not only to intimidate carnivorous dinosaurs but also for “sexual display,” such as disputes between peers (fighting over females or territory).
Recent research has revealed that their strength was not as high as the tail spikes of a Stegosaurus, but they still packed enough power to make an opponent flinch in close quarters.

Offense and Defense Against Predators: Anti-Tyrannosaurus Tactics

The Attacking “Dawn Tyrants”

Roaming North America at that time were ferocious predators like Albertosaurus and Daspletosaurus, which could be called “Dawn Tyrannosaurs,” and Edmontonia was one of their targets.

Intense Counterattack from a “Prone” Position

While their backs were iron-clad, their bellies lacked armor and were in a “no-guard state.”
If flipped over, it would be fatal.
Therefore, when attacked by an enemy, they adopted the following tactics:

Defense

Utilizing their low center of gravity, they would drop flat to the ground to hide their weak abdomen.

Counterattack

Against enemies that persisted, they would move forward, thrusting their massive forward-facing spikes to deliver a powerful piercing blow to the attacker’s legs.

This integrated tactic of offense and defense wounded the legs of Tyrannosaurs and supported their survival.

The Drama of Three Species and History of Classification

A 10-Million-Year Evolutionary Relay

During the last approximately 10 million years of the Cretaceous period, the following three species appeared in North America in order:

• Edmontonia rugosidens
• Edmontonia longiceps
• Edmontonia schlessmani

The final species, schlessmani, coexisted with star dinosaurs like Ankylosaurus, Tyrannosaurus, and Triceratops, witnessing the end of the dinosaur era.

Fluctuating Classification and Names

There have been changes in its classification, and at one time, it was given different genus names (such as Chassternbergia or Denversaurus).
Regarding Denversaurus in particular, a view was presented at a 2015 academic conference stating that “it is sufficiently possible to view it as a separate genus,” making it a subject of very interesting debate.

Unexpected Mobility and a “Gourmet” Side

A “Heavy Tank” That Wasn’t Sluggish

Although it looks heavy, it actually had relatively long legs for an armored dinosaur and is believed to have been able to move faster than other armored species.
This unexpected mobility also aided its survival.

A Gourmet Practicing Selective Feeding

Its snout was relatively narrow, making it suitable for selecting specific plants rather than eating indiscriminately from the ground.
They are believed to have practiced “selective feeding,” preferring high-nutrient ferns and young shoots, making them “gourmets” adapted to their environment.