Stegosaurus: Body Like a Bus, Tiny Little Brain

Hollywood, take heed. Movies like "Fantasia" and the camp classic "Planet of Dinosaurs" showStegosaurusduking it out with everyone's favorite bone-crusher,Tyrannosaurus rex. There's just one problem: Those two dinos never crossed paths in real life.

Tyrannosaurushad a fairly short reign that lasted from 68 to 65.5 million years ago.Stegosauruscame and went much,muchearlier. The oldest specimens on record are around 155 million years of age — while the youngest were fossilized 150 million years before the present.

So the mightyT. rexactually livedcloser to the dawn of mankindthan it did toStegosaurus's heyday.

TheJurassic Period, which lasted from 199.6 million to 145.5 million years ago, was drawing to a close whenStegosaurusroamed Earth. Although its rangeincluded Portugal,beast is mainly known fromfossilsites in western North America.

Stegosaurusbelonged to a suborder of dinosaurs called — what else? —the stegosaurs.

Found in North America, Europe, Asia and mainland Africa, the stegosaurs walked on four legs and had long, beak-tipped skulls.

But it's the ornaments that really grab your attention. Spikes were a stegosaur mainstay, adorning the tails of every known species. Many of these creatures, like Africa'sKentrosaurus, also rocked big old spikes on theshoulders and lower back.

And where the back spikes came to an end, a much weirder feature took over.Stegosaurusand its kin are characterized by thevertical platesabove their spines.

We may never know how these things functioned. Paleontologist Othniel Charles Marsh namedStegosaurusin 1877. He chose this name — which, again, means "roofed lizard" — because he figured the plates were sheets of armor that laid flat against the animal's backside.

Instead, later discoveries proved the objects stood upright, leaving the flanks on these dinosaurs exposed.

Because the plates containedblood vessels, experts used to think they helped stegosaurs chill out. Heat would supposedly dissipate from blood as it entered the tall, fanlike structures. After this chilled blood circulated elsewhere, it'd stay cool for a little while — lowering the overall body temperature.

This hypothesis is no longer popular. According to a studypublished in 2005 in the journal Paleobiology,blood-carrying networksinStegosaurusplates were there to promote healthy bone growth — but they played no role in dissipating body heat.

MaybeStegosaurusand its kin were just showing off. Made of bone and encased inhorny sheaths,plates could've made these dinos look bigger and more intimidating.

Capable of hitting 29.5 feet (9 meters) in length and weighing 5 tons (4.5 metric tons),Stegosauruswould loom large over today's land mammals. Even bystegosaur standards, it was a biggie; most of the dinosaurs in that group were only 13 to 23 feet (4 to 7 meters) long.

Yet in the late Jurassic,Stegosauruslived in the shadows of behemoths. Sauropods — or "long-necked" dinosaurs — like the 60-foot (18-meter)Camarasaurusand the 80-foot (24-meter)Diplodocuswere some of the creature'sneighbors.

And whileStegosaurusdidn't have to worry aboutT. rex, a rogue's gallery of Jurassic predators stalked its ecosystem.

Allosauruswas especially common. Measuring up to 28 feet (8.5 meters) long, this carnivore had serrated teeth and jaws that couldopen wideat a terrifying 79-degree angle.

Good thingStegosaurushad four tail spikes at its disposal. We know they saw action once in a while; a study published in "The Armored Dinosaurs" by the Indiana University Press in 2001 that reviewed 51 of these dangerous-looking fossils found clearevidence of traumaon 10 percent of them.

显然,用不带“屋顶的蜥蜴”. OneAllosauruspubic bone shows a deep wound thought to have been made by aStegosaurustail spike. All's fair in love and war, even Jurassic crotch-shots.

It seems there were plenty of injuries to go around; aStegosaurusneck plate that someAllosaurusprobablygnawed onhas been recovered from the Cleveland-Lloyd Dinosaur Quarry in Utah.

Paleontologists thinkStegosaurusbrowsed on low-lying vegetation like cycads. A 2016 computer simulation found the animal'sbite forcewould've rivaled that of a sheep or cow.

However it processed food, this dinosaur didn't need much gray matter.Stegosaurushad a brain cavity that was long, narrow —and tiny. Tipping the scales at 20.8 ounces (80 grams) or so, the actual brain only made up about 0.001 percent of the creature's total body weight.

Note that we said "brain" and not "brains."

Absurd as it might sound, there's a rumor thatStegosaurushad asecond brainlocated where the sun doesn't shine. Writing in 1881, Marsh drew attention to the enlarged cavity we find in the backbones above this dinosaur's hip region. Then he went and called it a "posterior braincase."

And the rest is history.

No one knows what this opening was for, although some researchers think itstored glycogen, a sugar that provides cells with energy. Regardless, there's no reason to thinkStegosaurus— oranydinosaur — had multiple brains.

Stegosaurus has some pretty cool bragging rights, though. Not only is the Jurassic herbivore Colorado's officialstate fossil, but it was also the inspiration forGodzilla'sdorsal plates. Take that,Kentrosaurus!