Everything You Need to Know About T. Rex but Were Afraid to Ask

The tiny arms of a T. rex made an otherwise fearsome creature look like it had a flaw. New research says that might not be the case. sruilk/Shutterstock

Icons come and go, especially when it comes to the star-studded pantheon of dinosaurs.

One day, the triceratops is all the rage. Those distinctive horns, that 10-ton girth and ... is that a beak? But peace-loving vegetarian dinosaurs, no matter how interesting they appear, just don't have a long shelf life in the popular imagination.

Who wants to be remembered as king of the salad bar?

A 3D rendering of a tyrannosaurus rex fighting a triceratops
The T. rex wasn't the salad type. Herschel Hoffmeyer/Shutterstock

Then there was the upstart velociraptor! Fast. Smart. Vicious!

But much of that hype faded when paleontologists politely pointed out that velociraptors weren't quite the sprinting razor blades that terrified us in the "Jurassic Park" movies. They had feathers and probably looked more like big chickens. (Mean chickens, though.)

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And speaking of chicken, do you know who dined on many of these dinosaurs?

That would be the always-in-fearsome-fashion Tyrannosaurus rex.

It's been around 70 million years since the T. rex stalked the Earth, waving its twiggy arms around and treating its contemporaries like chicken.

But why is it that for humans — who only ever got to dust off their old bones — the nightmares remain so vivid?

Why doesn't the T. rex go the way of the relatively anonymous allosaurus — a creature that was, in fact, faster and meaner?

Well, maybe that's because the T. rex was so much more than the sum of its teeth. While ferociousness goes a long way towards building any animal's reputation, it doesn't make them a household name. Just ask the allosaurus.

No, the T. rex — from its parenting skills to its fascinating anatomy — has so much more to recommend itself to immortality.

But let's start with the obvious.

1. They Were Actually Pretty Ferocious

The skull of a tyrannosaurus rex
All we have to remember the T. rex by today are some intimidating bones. Marques/Shutterstock

Let's not beat around the bush here. The T. rex was one scary Cretaceous citizen. We're talking about a 40-foot long animal with 9-inch teeth — think railway spikes — that could effortlessly crunch through bone. As researchers found in a 2019 study published in The Anatomical Record, the high bite force of a T. rex was due largely to the rigidity of its skull, which helped convey the full force of its jaw muscles into those monstrous teeth.

"T. rex is just one of those very optimally built animals," study co-author Casey Holliday, a paleontologist at the University of Missouri, told National Geographic. "It has all these giant jaw muscles, and it's very efficient at taking that muscle force and putting it into its prey item because it has a stiff skull."

Its name is a mix of Latin and Greek — as if first coined by a flustered paleontologist too freaked out to get the ancient languages straight. But "Tyrant Lizard King" definitely gets the scary factor perfectly straight.

2. A T. Rex Could Beat You at Chess... If You Were as Smart as a Chimp

Well, maybe that's an exaggeration. A T. rex would be much likelier to eat the whole chess board — and you with it — than to declare "Checkmate!"

But scientists say that brain was twice the size of most of its peers, possibly even functioning at the same level as the modern chimpanzee. That mind, as opposed to muscle, is what really gave the T. rex its evolutionary momentum. In fact, the T. rex started out as a small, though brainy, creature. Fossils found in the Uzbekistan desert indicate their early ancestors were actually pint-sized predators who relied on superior wits to chew their way up the food chain.

As apex predators, they only evolved into living tractor-trailers over the last 20 million years of the reign of dinosaurs.

"Tyrannosaurs got smart before they got big, and they got big quickly right at the end of the time of the dinosaurs," Steve Brusatte, a paleontologist at the University of Edinburgh in the U.K., told Live Science.

An illustration of a T. rex.
In the case of the T. rex, brains came long before brawn. CapturePB/Shutterstock

3. Their Senses Were Also Razor-Sharp

Those big brains had other amenities too. Like massive olfactory bulbs allowing a T. rex to catch the faintest whiff of dinner and come running. Its sense of smell was, like so many things, far superior to its contemporaries. Even worse for those lesser-endowed animals was the possibility the T. rex enjoyed hunting them at night.

"Although the king of carnivorous dinosaurs wouldn't have passed on scavenging a free dead meal, it may have used its sense of smell to strike at night or to navigate through large territories to find its next victim," explained University of Calgary paleontologist Darla Zelenitsky in the Independent.

Oh, the good old days.

What's more, the T. rex's sense of hearing was equally sharp. Research on its inner ear, or cochlea, suggests a powerful array capable of picking up sounds from even the lowest frequencies.

And if one day you happen to visit a theme park where a T. rex that was reconstituted from ancient DNA is running amok, don't pin your survival on "Jurassic Park" tactics. A T. rex can see you very clearly — even if you stand stalk still. Those front-facing eyes, which probably looked like malevolent moons to quivering prey, packed pretty potent "binocular vision." Citing large regions of the brain that controlled sight, some researchers have even thrown around the term "hawk-like" vision.

A close-up of a T. rex's eyeball
The T. rex likely had eyes a little bigger than tennis balls. Martina Badini/Shutterstock.com

4. They Were More Into Power-Walking Than Running

Sprinting, on the other hand, wasn't the T. rex's strong suit. While past studies suggested this behemoth could run faster than a horse, more recent analysis indicates the animal's unique physiology actually held it back. Galloping was a major pain for a bipedal animal with a two-story-high skeleton — so much so that running might have broken its legs.

As a study published in the journal PeerJ notes, "True running gaits would probably lead to unacceptably high skeletal loads in T. rex."

In other words, you might have been able to run from a T. rex. But hiding? Not so much.

5. They Were Sensitive Lovers — When They Didn't Eat Each Other

In the face of all those terrifying talents, it's easy to overlook the T. rex's surprisingly sensitive side. For example, as hard as it may be to imagine, this toothy titan was a sensuous and tender lover.

Scientists say it's all about that nose — an organ as sensitive to the touch as our own fingertips. As a result, T. rex foreplay often involved generous amounts of face-rubbing.

That conclusion came on the heels of startling T. rex discovery. The creature's nose was a rare soft point in its armored hide — perforated by nerve openings. Those nerves likely made its face exceedingly sensitive to the touch.

"In courtship, tyrannosaurids might have rubbed their sensitive faces together as a vital part of precopulatory play," researchers noted in the journal Scientific Reports.

That's a lot of face-rubbing faith to put into a mate that's also prone to eating its own kind.

The T. rex was likely a fervent cannibal.

"It's surprising how frequent it appears to have been," paleontologist Nicholas Longrich noted in a press release. "We're not exactly sure what that means."

Well, for one thing it means if you're a T. rex, you really need to be sure that you've found the One.

6. Let's Talk About Those Arms

It's a good thing the T. rex was so "handy" with its face because those twiggy little arms don't seem like they were good for much. In fact, they may not have been long enough to even touch its face. And compared to those tree trunks it had for legs, they seem altogether inadequate.

Close-up of a plastic model of T. rex's arms
The T. rex may have kept its arms facing inward. JopsStock/Shutterstock

But once again, the T. rex may surprise us. Research presented to the Society of Vertebrate Paleontology suggests T. rex may have been able to rotate the palm of its hand inward and upward — essentially allowing its palms to face the chest. That means those arms weren't used for reaching out, but possibly hugging its prey nice and close to the chest. It's hardly conclusive, but when it comes to the T. rex, hypotheses tend to lean in the direction of how a body part helps it devour something.

7. Apparently They Had an 'Air-Conditioner' in Their Heads

We may not know if T. rexes were good at managing their anger, but according to one study published in The Anatomical Record, they were well-equipped to keep a cool head. The species had two large holes in the roof of its skull, called the dorsotemporal fenestra, which were long thought to hold muscles that helped with jaw movements.

But that seemed odd to Casey Holliday, a professor of anatomy at the University of Missouri who led the study. "It's really weird for a muscle to come up from the jaw, make a 90-degree turn, and go along the roof of the skull," Holliday said in a statement. "Yet we now have a lot of compelling evidence for blood vessels in this area, based on our work with alligators and other reptiles."

These holes are present in the skulls of both alligators and T. rex, and seem to be part of a cross-current circulatory system, the researchers say, which act like "an internal thermostat" to help the cold-blooded creatures warm up and cool off.

"We know that, similarly to the T. rex, alligators have holes on the roof of their skulls, and they are filled with blood vessels," explains co-author and Ohio University anatomy professor Larry Witmer. "Yet for over 100 years we've been putting muscles into a similar space with dinosaurs. By using some anatomy and physiology of current animals, we can show that we can overturn those early hypotheses about the anatomy of this part of the T. rex's skull."

illustration of T. rex, alligators and a bird in thermal view
This illustration shows a thermal view of a T. rex with its dorsotemporal fenestra glowing on the skull. Brian Engh

This illustration shows a thermal view of a T. rex with its dorsotemporal fenestra glowing on the skull. (Image: Brian Engh)

8. They Took Their Parenting Responsibilities Seriously — at Least in the Beginning

When you're as good a lover as a T. rex, you can expect more than a few baby meat-cleaving lizard kings to start popping up around the den. And in the domestic realm, the T. rex once again showed a sensitive touch. Those keen noses sniffed out the ideal place for a nest — often in the wide open because ... come on, who's going to raid a T. rex nest?

Meanwhile, their super-sensitive faces ensured fragile eggs were gently moved around. Even baby dinosaur kings had to be moved around from time to time — without accidentally being popped like grapes between those tensor jaws.

In fact, as fond as tyrannosaurs were of gobbling up the eggs and freshly hatched babies of its neighbors — pity the oft-preyed upon Stegosaurus! — their own parenting habits are largely a blank.

There's a surprising dearth of T. rex juveniles in the fossil record. What happened to those babies that their parents were so careful not to break?

We know at least some of them grew up to be big and terrifying. But where did all those T. rex babies go — despite all the care their ferocious meat-eating parents may have put into hatching them?

Okay, so maybe we just answered our own question.