10 Hardy Facts About Euoplocephalus

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Life in tyrannosaurid country forced Euoplocephalus to develop some extreme safety features. (You know you’re dealing with one tough customer when armor-plated eyelids are involved.) Here are 10 more things you might not know about this fascinating herbivore.

1. Its Terrifying Tail Club was Supported by Bony Tendons.

The far end of Euoplocephalus’ tail was basically a rigid hammer thanks to these rods. In action, powerful muscles near the tail’s more flexible base swung that half around with potentially bone-splintering force.

2. Euoplocephalus Probably Wasn’t the Sharpest Knife in the Drawer.

We’ll never know how intelligent an extinct animal truly was—after all, objectively assessing a live creature’s brain power is nearly impossible. Still, a popular tool called the “encephalization quotient” might help point us in the right direction. By measuring a given creature's brain mass, then dividing that number by whatever brain mass we'd expect an animal of that size to possess, we land at an EQ estimate for the beast in question. 

Supposedly, the brightest critters get the highest numbers. For the record, we self-aggrandizing humans have an average EQ of 5.28 while platypuses and their kin lag far behind at around 0.87. In 1979, paleontologist James Hopson tried to calculate an EQ for Euoplocephalus. His result: 0.52.

3. It Was a Pretty Decent Masticator.

Mammals totally trump reptiles in the chewing department. Since dinosaurs couldn’t move their lower jaws from side to side the way people do, most would have either swallowed foodstuff whole or mashed it up by slamming their teeth together in a straight, vertical motion. Euoplocephalus, on the other hand, had a more complicated technique: By pulling its lower jaw backwards, this dino’s pearly whites could tear apart its vegetarian entrees with ease.

4. Generally, Euoplocephalus Let Its Tail Club Hang Low.

★Kumiko★, Flickr // CC BY-SA 2.0

Given the proportions of Euoplocephalus’ tail and hind legs, the tail, when being used for fighting, was likely suspended “just above the ground, neither dragging nor being greatly elevated.” At least, that’s what dino locomotion expert Walter P. Coombs Jr. concluded in 1995. 

5. Toy Manufacturers Keep Shortchanging Euoplocephalus.

For 56 million years, body armor was all the rage thanks to the ankylosaurid family. One could argue that, scientifically, Euoplocephalus is this brawny gang’s best-known genus due to an abundance of specimens—though many of these probably came from different dinosaurs (see below for more on that).

In a perfect world, Euoplocephalus would be a household name. Unfortunately, its bigger cousin Ankylosaurus keeps hogging the spotlight—there's a Godzilla villain named in its honor, it has an upcoming Jurassic World appearance, and plastic toys clearly based on Euoplocephalus are often mislabeled Ankylosaurus.

6. Euoplocephalus Had Some Weird Neck Armor ...

Several bony plates were fused together in an arch-shaped block that was draped over Euoplocephalus’ neck. Called a cervical half-ring, this odd structure can only be found in ankylosaurs.

7. … And Even Weirder Nasal Passages.

Get a whiff of this, folks: Apparently, inward breaths had to take a circuitous path from the dino’s nostrils to its lungs. Twisted Euoplocephalus nasal passages are so erratic-looking that they’ve even been compared to novelty crazy straws. Perhaps this convoluted mechanism evolved to help cool down the brain. Or maybe Euoplocephalus used its schnoz to produce deep, resonant sounds. Both explanations make sense.

8. Like Many Ankylosaurs, It Had a Really Wide Ribcage.

Generous midsections not only make Euoplocephalus and company really hard to draw, they also hint at a heavy-duty digestive system. Ankylosaur rib cages were almost as wide as their equally outrageous hips, leading paleontologists to suspect that the herbivores’ huge abdominal regions acted as massive fermentation chambers, made to break down the fibrous plants these guys ate. By the way, if this hunch is accurate, suffice it to say that you wouldn’t want to light a match near one. 

9. Euoplocephalus May Have Mated Feline-Style.

How did two enormous animals that were essentially legged tanks copulate? Ankylosaur specialist Ken Carpenter offered a decent hypothesis in his 2000 book Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction. “[A] common method,” he writes, “might be for the female to squat on her forelimbs, raising her rear to the air (sort of like a house cat). In this position, with the tail off to one side, the cloaca is well exposed. The male could mount her from behind to one side and support himself with his forelimbs on her back.” For you visual learners, Carpenter drew a picture for you.

10. It Likely Wasn’t Quite as Successful as We’d Assumed.

Euoplocephalus was once something of an aberration. After its discovery in 1902, the animal went on to become North America’s most commonly-found ankylosaurid by a cozy margin. Moreover, there was only one species within this genus: Euoplocephalus tutus. E. tutus, it was thought, lived from 76 to 67 million years ago, an unusually long span by species standards.

Euoplocephalus was heavily revised in 2013 by then-Ph.D. student Victoria Arbour. As part of her doctoral research, Arbour took a good, hard look at every available specimen and concluded that, in actuality, four separate species—Scolosaurus cutleri, Anodontosaurus lambei, Dyoplosaurus acutosquamens, and Euoplocephalus tutus itself—had all been wrongly lumped together under the name E. tutus. Hence, she argues that good old Euoplocephalus really lasted a scant 2 million years. If you’ve got the time, check out "Who-oplocephalus? Euoplocephalus!" Arbour’s excellent, pun-tastic talk: