Spikes, Armor & Hard Heads: Dino Defenses?

Dinosaurs definitely rocked some bizarre looks: bony plates running down their backs, horns jutting out from their faces, spikes on their tails, armored plates, shield-like frills around their heads. They looked ready for battle. No surprise. Dinosaurs needed some good defenses with the likes of Tyrannosaurus rex and Spinosaurus running around, ready to snatch smaller dinosaurs up for their next meals.

For a long time, dino fans and scientists alike marveled at the amazing variety of defenses and weapons that dinosaurs displayed. But lately, scientists have been studying how the strange body parts evolved and functioned. They examined several theories and came up with a shocking conclusion: Some of those so-called “defenses” were not great protection after all!

Take, for example, dinosaur horns. Paleontologists are people who study the fossils of animals and plants, the remains or impressions preserved as molds or casts in rocks. When the fossils of the first horned dinosaurs were found on Triceratops, paleontologists thought these were probably used for defense. “You have these iconic images of Triceratops doing battle with Tyrannosaurus rex,” paleontologist Caleb Brown told the Canadian newspaper Calgary Herald. But as scientists discovered more and more horned dinosaurs over the past couple of decades, they realized that the horns and frills (the big shield-like parts) varied a lot among those dinosaurs. That was an important clue — and one that raised doubts about them being used mainly for defense.

Nature tends to figure out the best way of doing things, including how to protect an animal. If horns and frills were the answer, one shape and arrangement of them would have provided better protection than other shapes and arrangements. Over time, all of the different types of horned dinosaurs (a group that scientists call “ceratopsians”) would have evolved to have that ideal protection — or at least something very similar. Rhinos, for example, have one or two horns at the end of their snouts — nowhere else.

But the ceratopsian dinosaurs had an amazing variety of horn and frill arrangements. The famous Triceratops had three spikes — two large ones above its eyes and a smaller one on its snout — and a slightly jagged frill. Regaliceratops, had a much larger nose horn and a large, crown-shaped frill, but only stubby little horns over its eyes. Styracosaurus rocked four to six spikes jutting out from an extra-long frill, and two little horns poking out from its cheeks in addition to a large nose horn. Centrosaurus had just one large horn on its snout but many small ones edging its frill, including a couple that curled forward.

“There are a number of species where their horns would be pretty much useless in defense,” said Brown, who discovered Regaliceratops. “What we’re thinking now is that these were used for display. These were to impress members of the same or opposite sex and communicate with other species. That plate at the back of his skull is pretty much a billboard advertising for that individual.”

Fancy frills — the fancier, the better — helped the dinosaurs get the attention of possible mates. They were all about looking good, putting on a display — like how a peacock spreads its beautiful feathers. Does that mean frills and horns were only for display? Not at all! The ceratopsians’ horns may have added to their dashing looks in the eyes of potential mates, but they also probably helped the dinosaurs fight off rivals — much like two male antelope will lock horns and push each other back and forth until one gives up and leaves. And if a T. rex is coming after you, you use whatever you have to defend yourself!

Over the years, scientists also wondered whether the horns and frills helped the animals recognize members of their own species or maybe even helped decide who was the top dino in a group. But most scientists have ruled out those theories. These days, they generally agree that these amazing and bizarre body parts evolved mainly for display. The horned-and-frilled dinosaurs were lovers, not fighters.

The same goes for the standout features on other dinosaurs. Pachycephalosaurus had a huge, helmet-like skull that was about 20 times thicker than other dinosaurs’ skulls and ringed with short, spiky horns. It was easy to picture Pachycephalosaurs charging head-first into predators or rivals — much like bighorn rams butting heads. But that’s not likely. Scientists haven’t found scars suggesting the dinos rammed into things. Plus, the dinos’ necks were probably curved — not straight and rigid enough to be used as battering rams (or to crash through walls. Sorry, Jurassic World.) So what good were those domes? A dashing dome probably helped the dino attract a mate. And if a rival tried to steal the mate away, Pachycephalosaurus may have whacked it with its dome — but on the side, not straight on.

Even the huge club at the end of Ankylosaurus’s tail was mainly for show, advertising the animal’s health and strength to potential mates. But yes, if Ankylosaurus needed to protect itself, it probably swung that club — scientists found a couple damaged fossil tail clubs that looked like they had smacked something. But charging into battle with tail swinging? Nope. Same story for the dino’s tank-like armor, which included spikes running along its body and jutting out from its head. The armor probably helped protect the dino, but scientists think it was more important for looking tough in front of rivals. As it turns out, Ankylosaurus’s weird shape probably offered more protection than its armor. On the science news website, Live Science, paleontologist Kenneth Carpenter described Ankylosaurus as being wide and relatively flat: hard for a predator to get a firm grip on it — even without all the armor.

By now, you can probably guess why Stegosaurus had a row of bony plates running down its back: to attract potential mates and scare off rivals. For a while, scientists thought the plates might help the dinos cool down when they were too hot or soak up some warmth when they were too cold. But now we’re pretty sure that the plates were for display — though they may have offered some protection, too. The spikes at the end of Stegosaurus’s tail also may have attracted mates, but paleontologists found plenty of evidence that Stegosaurus used them for defense, too. On many fossils, the sharp spike tips had been broken off but then started to heal, growing new bone. Stegosaurus probably slashed an attacking predator if they were side by side. But if the predator came in at an angle, Stegosaurus’s spikes might drive in so deeply that they’d get stuck and break off.

It’s cool to think of frills as shields and horns as weapons, and kind of disappointing to learn they only sometimes used their horns, frills, and spikes. It turns out that, more often, they relied on defenses similar to what animals use today. Many plant-eating dinosaurs — including Stegosaurus, horned-and-frilled ceratopsians and others — found safety in numbers, eating and traveling in herds, like modern-day wildebeest or springbok antelope. Speedy dinosaurs like Velociraptor and Gallimimus  — bird-like theropods that ran on two legs — could run away from trouble (though, as predators, they often used their speed to catch their next meal). And like modern adult elephants, the massive, long-necked sauropods’ size kept them safe from predators, though they often stayed in herds to protect their young.

It’s possible that some dinosaurs even relied on camouflage. Paleontologists recently found rare dino fossils with well-preserved skin — one of a horse-sized ankylosaur called Borealopelta and another of a pony-sized ceratopsian called Psittacosaurus — which showed they were light-colored on the bottom and darker on the top, a camouflage pattern known as countershading.

Though the craziest dino body parts were mainly for attracting mates and fighting off rivals — and only rarely for defense — dinosaurs had a wide arsenal of defenses. Size, speed, coloring, and hanging with their buddies helped them survive in their wild world.