National Geographic News
A silhouette of a Tyrannosaurus rex fossilized skeleton.

Jurassic Park is the best film portrayal of a Tyrannosaurus rex to date, experts say. But was the real T. rex—a fossilized skeleton of the dinosaur is shown here in silhouette—more terrifying than imagined?

Photograph by Louie Psihoyos, Corbis

Brian Switek

for National Geographic News

Published April 5, 2013

Part of our weekly "In Focus" series-stepping back, looking closer.

No dinosaur is more cherished than Tyrannosaurus rex. The Cretaceous king of the tyrants epitomizes the size, ferocity, and bizarre nature of dinosaurs that continues to enchant us. We're so smitten with T. rex that we are continually bringing the dinosaur back to life through art and film.

Perhaps no restoration of the great carnivore has been as influential or celebrated as the genetically engineered tyrant that terrorizes Jurassic Park, which is being re-released in 3D today. Revived through computerized special effects and puppetry, the film's T. rex is a muscular, agile predator far more imposing than the tottering, tail-dragging representations that had appeared on film before. And in the 20 years since Jurassic Park debuted, as knowledge about T. rex has increased, the dinosaur has become even scarier still.

"It's hard to pick a single coolest discovery about Tyrannosaurus rex itself over the last 20 years," says University of Maryland tyrannosaur expert Thomas R. Holtz, Jr. Paleontologists have started to understand how drastically T. rex changed as it grew into an adult and to make sense of the neurological "CPU [central processing unit] and sensors of the killing machine" that made T. rex so deadly, says Holtz.

Beware the Maw

Of all the dinosaur's traits, the maw of T. rex has probably inspired the most nightmares—and much of the cutting-edge science. The predator's deep, reinforced skull was set with an array of thick, serrated teeth that evolved to pierce and cut simultaneously.

Jurassic Park's T. rex put that impressive array of dental cutlery to work on the hapless lawyer Donald Gennaro and a fleeing Gallimimus, as well as a pair of raptors at the film's climax, but the predator had an even more formidable bite than the movie portrayed. Last year, researchers Karl Bates and Peter Falkingham announced that an adult T. rex had a bite force of almost 12,800 pounds—the most powerful estimated bite force of any terrestrial predator. Considering the damage a full-force T. rex bite would have inflicted, Jurassic Park's tyrannosaur looks as if it's being downright gentle with its prey.

Jurassic Park imagined how T. rex used its weaponry, but there is actual evidence of T. rex biting techniques in the fossil record. After T. rex made a kill or found a carcass to scavenge, it could be a delicate feeder. As Denver Fowler and colleagues presented at the annual Society of Vertebrate Paleontology meeting last fall, toothmarks on Triceratops skulls hint that T. rex had a step-by-step method of decapitating Triceratops.

Yet the destructive power of T. rex wasn't isolated in its jaws. The dinosaur's neck muscles played a major role in the carnivore's ability to kill and consume prey. In their 2007 study of T. rex feeding mechanics, Eric Snively and Anthony Russell found that the dinosaur's neck muscles were so strong that the tyrannosaur could have thrown a 110-pound chunk of meat 15 feet into the air and caught it again—a frightening ability known as "inertial feeding." Rather than shake the movie's lawyer from side to side like a dog, a real T. rex might have tossed Gennaro into the air with a flick of its neck, catching him as he fell back toward all those teeth.

Deadly Bite

T. rex didn't use its teeth and jaws just to pierce the flesh and crush the bones of prey. Tyrannosaurs also bit each other. Healed wounds on the skulls of tyrannosaurs—such as the teenage T. rex nicknamed Jane—show that these theropods tussled by biting each other on the face. (Arm wrestling wasn't an alternative, apparently, though T. rex's small arms were heavily muscled and strong for their size.)

This bit of prehistoric behavior might explain why some of the largest carnivores of all time were ultimately killed by much smaller organisms. The lower jaws of many T. rex are pockmarked with smooth-sided holes. Some researchers thought that these were bite wounds from fatal attacks by rivals, but in 2009 Ewan Wolff and colleagues proposed that these injuries were created by tiny microorganisms that cause the same kind of damage in birds of prey. The protozoans infest the upper digestive tract of the birds, creating ulcers and lesions before eventually boring into the bone. The feathery raptors catch the little hitchhikers by eating infested pigeons.

Perhaps T. rex picked up similar microorganisms through dinosaur-to-dinosaur transmission. Face-biting would be a direct way for the harmful microorganisms to jump from one T. rex to another. Thanks to tooth-damaged bones, researchers also know that tyrannosaurs cannibalized each other and could have picked up parasites that way. Regardless of the pathway, it would seem that the bite of a tyrannosaur wasn't deadly just to prey, but to other tyrannosaurs, too.

Fearsome but Not Fast ... and Feathered?

Even when paleontologists downgrade the abilities of T. rex, the dinosaur still seems scary. One of the most famous scenes in Jurassic Park is the Jeep chase, with an angry T. rex almost making a snack of the smarmy chaos theorist Ian Malcolm. Could T. rex really run fast enough to keep up with a speeding car? The work of researcher John Hutchinson and colleagues suggests not.

For one thing, the movie's T. rex wasn't actually moving very fast. The escaping Jeep looks like it's moving 40 miles per hour or more, as Hutchinson explains on his lab's website, but the dinosaur's movement—it always has one foot on the ground—indicates that the T. rex is moving only about 10-15 miles per hour. This fits what the dinosaur's skeleton suggests about its speed. By Hutchinson's calculations, T. rex walked about 6 miles per hour and ran about 15-25 miles per hour. A top speed of 25 miles per hour may seem meager, but the only humans able to exceed it are highly trained Olympic athletes. If you were unfortunate enough to be caught off guard by a T. rex out in the open, you'd stand no chance of outrunning the carnivore.

Picturing the tyrant wearing feathers—a likelihood since two other tyrannosaurs have been found with coats of dinofuzz—may change its image a bit. As researchers have filled in the deep history of the dinosaur, they have determined that the earliest Jurassic tyrannosaurs were "small, fast, and fuzzy ... not much at all like the giant T. rex of Jurassic Park," says Holtz.

But to date, Jurassic Park's T. rex is the best committed to film. "I think the movie pretty much nailed it," Hutchinson says, "as much as 'it' can be nailed, given the uncertainties." Holtz agrees: "The movie gave Tyrannosaurus a seriously high but justifiable level of awesome," he says, as the dinosaur's behaviors shown throughout the film series include "parental care, family hunting, puncture-and-pull feeding, chasing prey with a fast walk." If anything, what was on screen was "not too different from the Tyrannosaurus behaviors we would interpret today." (See related story: Writer Revisits Teenage Love of Jurassic Park)

Sadly, we're never going to get to witness a living T. rex chase after dinosaurian prey—or even after us—to know for sure how closely Jurassic Park's informed speculation matches reality. The movie's intricate puppets and special effects dinosaurs may be the closest we ever come to seeing a tyrannosaur walk the Earth again. When you revisit Jurassic Park and watch T. rex howl its terrifying cry of freedom as it stomps out into the stormy night, you will be experiencing the best cinematic tribute to one of the most awesome carnivores to have ever evolved.

Shelly Kekes
Shelly Kekes

The videos links offered on the left column are not working, well, I only tried two.  (The endangered shore-bird, and hiding historical treasures videos.)

the won
the won

  @Carter Peterson... Look at the evolution of the Horse, from 5 toes to one with the "chestnuts" vestigial toes moving up the leg... Same sort of premise. If the arms were superfluous, but the animals were successful enough to breed than, their "attenuated" shape sort of makes sense. I guess the animals that didn't waste energy on growing arms were more successful and eventually the mutation became dominant.

Carter Peterson
Carter Peterson

From an evolutionary standpoint, I've never understood the attenuated "arms" of a T-rex.

Debra Hall
Debra Hall

The T Rex in the film was cool , but  the Velociraptors really scared the pants off me !

A. Volk
A. Volk

Thanks for the article, Brian. Your last paragraph made me chuckle when you said, "Sadly, we're never going to get to witness a living T. Rex chase after dinosaurian prey..." 

Didn't you see Jurassic Park? Didn't turn out so great for the humans if I recall correctly ;)

craig hill
craig hill

Too bad the rerelease of Jurassic didn't add some shaded designs along T Rex's body, and that of some of the other dinos, if not a little feathering.  How hard would that have been?  Not. 

Kyle Carlson
Kyle Carlson

@Carter Peterson  the arms are just vestigial organs much like our appendix... we as a species don't need it but do to our DNA it will get significantly smaller with less use over time.

Lee Parsons
Lee Parsons

@craig hill Actually, that would be rather difficult as the CGI work for the movie was done on hardware that is now approaching 20 years old.  If the old hardware still exists anywhere, it likely isn't in working condition.  Even if they could find some old SGI workstations in operating condition, they would need to load the software, find the original files, etc.  It is unclear if there even exists modern software that could read those old files directly as CGI software has changed a lot since then.  

So actually, it would be quite an undertaking.  And of course even if you reach that point, you still need artists to then go in and do the work.  

Carl West
Carl West

@Kyle Carlson @Carter Peterson The appendix application has been found and it is a sound purpose, if in the course of digestion you were to take a bunch of antibiotics, they wipe out ALL the bacteria good and bad in your digestive track. the appendix then is used to kick start the bacteria into the digestive system and your off and running again in no time, and I do mean no time at all, were you to replace that bacteria al natural you would be sick for a week or more to ingest the right foods to restart. hum funny how nature uses things hu? so just don't cut something off and throw it away cause you don't know what it does. Say larger appendages would be more susceptible to damage in an attack and possible bleeding to death, them guys had big chompers.


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