Buzz
While the popular image of the Tyrannosaurus rex portrays it as a terrifying, solitary predator that roared through the landscape, indiscriminately devouring anything that moved, the truth is more complex. These creatures had a different appearance and sounds, were social animals, and engaged in behaviors even more horrifying than we imagined. However, not everything about them was just bloodshed and terror. The bones of T. rex have also provided crucial answers to long-standing paleontological mysteries.
10. They Had Lips
T. rex might not have been as toothy as we thought. A recent study suggests that this fearsome dinosaur could have had lips that completely concealed its razor-sharp teeth. Unfortunately, this discovery could eventually dispel the iconic image of a permanently exposed, crocodile-like grin.
The terrifying fangs of the Cretaceous predator were covered with a thin layer of enamel. To prevent decay—especially given their delicate nature—this enamel needed to stay moist. Modern-day reptiles, such as the Komodo dragon, provide support for this theory, as all large land-dwelling lizards have enclosed teeth.
On the other hand, their lipless relatives, like crocodiles, inhabit water, which means they don't need the extra moisture. Since T. rex lived on land and terrified everything it encountered, not the waters, it’s quite plausible that it also required lips to maintain its 10–15 cm (4–6 in) teeth in top condition.
9. They Lived and Hunted in Groups
This is a moment in history you wouldn’t want to revisit. In western Canada, scientists discovered the tracks of three tyrannosaurs moving together. Although no path of destruction was found, the tracks revealed fascinating behaviors and offered new insights into the dinosaurs’ lives.
These were battle-hardened, successful adults. The trio had clearly mastered survival in a harsh, predatory world. All three were around 30 years old, a remarkable age for T. rex. Skin impressions were still visible in the well-preserved tracks, even showing the severed claw of one T. rex’s left foot.
They walked together but kept a cautious distance. This 70-million-year-old trackway is the first of its kind, revealing T. rex tracks and providing the strongest evidence yet that these creatures did, in fact, form herds.
8. The Teenage Menace
There’s a reason the Canadian Three kept their distance from each other. From a young age, T. rex juveniles engaged in brutal battles. One such adolescent fossil, named "Jane" (gender unknown), was bitten to the bone by another temperamental teen.
Jane’s snout and upper jaw were severely damaged in the attack, breaking her nose. The injury was inflicted by a peer of a similar age, as her teeth matched the size and shape of the scars. Jane died at around 12 years old, though by then her snout had healed, albeit slightly flattened. This indicates the battle happened when she was younger.
At just 12, Jane was already a force to be reckoned with. Though small compared to an adult T. rex, she measured 7 meters (22 feet) in length and nearly 2.5 meters (8 feet) at the hip, weighing an impressive 680 kilograms (1,500 pounds).
7. The Gender Revelation
Paleontologists continue to face difficulty in distinguishing between males and females. Even species equipped with frills, horns, plates, and spikes don’t show clear sexual characteristics, often appearing mysteriously identical.
Enter MOR 1125. This seemingly ordinary label is associated with a groundbreaking discovery—tyrannosaur remains from a confirmed female. Molecular biologists have developed a method to identify female dinosaurs, all thanks to MOR 1125.
Her femur revealed that she was pregnant when she died. Inside, a special type of tissue, known as medullary bone, was found. In modern birds, this is essentially a positive pregnancy test.
The researchers put the tissue through numerous tests to eliminate the possibility of disease, and were successful. The tissue was found to match medullary bone both chemically and structurally. This discovery confirms that, like birds, a sharp increase in estrogen caused the formation of true medullary bone in pregnant dinosaurs.
6. T. Rex Made Its Own Meal
The violent interactions between species didn’t stop at broken noses. If food was available and T. rex was hungry, it wasn’t above having a meal that could include its own relatives, even if it meant chewing on cousin Bob.
The ancient predator required a significant amount of meat to sustain itself. Fossilized feces containing partially digested bones and flesh suggest a rapid metabolism, possibly accompanied by frequent hunger pangs driving the dinosaur toward its next meal.
The idea that T. rex was a cannibal has been well-established in scientific circles for some time. Separate finds of tyrannosaur bones showing the distinctive damage from serrated teeth confirm that they did indeed feed on one another. Researchers are still unsure whether T. rex actively hunted its own kind or scavenged from the dead, though it’s likely that both occurred.
5. Folding Teeth
It's clear that the jaws of a tyrannosaur could easily belong in a slasher film. Their violent purpose is impossible to ignore. However, the lethal bite didn’t only come from the obvious source. T. rex's teeth were also engineered for killing from within.
Each tooth featured serrations like a steak knife. What were initially thought to be cracks caused by high-impact biting and tearing were actually revealed by recent research to be internal folds.
These deep folds within the tooth helped keep it sharp and stable, reducing the likelihood of being damaged by struggling prey. This unique dental feature was found in T. rex and other carnivorous theropods. It’s likely that this ability to retain deadly fangs played a role in why these dinosaurs ruled as the largest meat eaters on Earth.
4. Nanotyrannus
In 1988, paleontologist Robert Bakker proposed that a T. rex-like skull was from a new species, Nanotyrannus. The Cleveland Museum fossil was much smaller, narrower, and had more teeth compared to the stockier head of a typical tyrannosaur.
But could this be a delicate relative or simply a juvenile T. rex?
Few believed that T. rex could undergo such drastic changes as it grew, leading to years of debate. Then, in 2001, the most complete juvenile T. rex ever found was unearthed in Montana.
It turned out to be Jane, the young dinosaur we mentioned earlier. This half-grown specimen provided the crucial link that connected the Cleveland skull to T. rex. She had the jawbone features that had previously been thought exclusive to the smaller Nano.
Nanotyrannus became irrelevant. However, what replaced it was the understanding that T. rex underwent significant changes in its appearance throughout its various growth stages.
3. They Didn’t Roar
To uncover the true sound of T. rex, a study focused on today's closest living relatives—archosaurs, such as crocodiles and birds. By analyzing how they vocalize, researchers determined that large dinosaurs like Tyrannosaurus didn’t produce earth-shaking roars, as often depicted in popular media.
If T. rex resembled its feathered relatives, it likely lacked vocal cords and instead possessed air sacs, possibly even a bird-like syrinx. Without vocal cords, T. rex would not have been capable of roaring.
When T. rex needed to communicate, it would have inflated these air sacs to produce sounds without opening its mouth, much like some larger bird species do. The sounds of this iconic dinosaur would have been far less dramatic—closed-mouth rumbles and chirps.
2. Decapitation Specialists
Researchers were captivated by the Triceratops‘ neck frills, which revealed an unexpected behavior from T. rex. Bite marks corresponded to the predator biting and even tugging on the frills.
Each examined fossil of the prey revealed that the T. rex seemed to develop an odd interest in the bony frills, even though the prey was already dead. Scientists, puzzled as to why the dinosaur would nibble on something without meat, investigated further. What they uncovered was shocking.
Adult T. rex appeared to have a disturbing habit of decapitating Triceratops. What was once thought to be a nibble turned out to be a forceful tugging, allowing T. rex to sever the head of its prey.
Triceratops‘ neck muscles seemed to be the prime target, with the bony frill obstructing access. Several Triceratops fossils also showed slash marks on the neck joints, suggesting that the herbivore’s head had been ripped off.
1. Intelligence Made Them Apex Predators
Another gap appeared in the T. rex timeline, specifically in its evolution. Interestingly, it involves a smaller tyrannosaur. This creature, a relative, was an ancestor named Timurlengia euotica.
Experts had long struggled to explain how the first horse-sized precursors evolved into the mighty apex predator that would later weigh over seven tons. Timurlengia may hold the key. Its braincase suggests a level of intelligence more akin to a math genius and could reveal that cleverness, not sheer size, played a pivotal role in T. rex‘s rise to power.
The tyrannosaur lineage spent millions of years as secondary players to larger carnivores. It was only when T. rex‘s competitors mysteriously vanished that they ascended to the top of the food chain.
When the opportunity to become the apex predator arose, they already had the intelligence and heightened senses necessary to outcompete others. Interestingly, their iconic massive size didn’t develop until later, towards the end of the dinosaur era.
