Tyrannosaurus Rex may have been the king of the dinosaurs, but you may not know much about this fearsome meat eater except that it was a) very, very big and b) very, very dangerous. Here are 10 pertinent facts about this Cretaceous carnivore. (See a gallery of Tyrannosaurus Rex pictures.)
1. T. Rex wasn't the only tyrannosaur.
Tyrannosaurus Rex gets all the press, but the fact is that many other genera of tyrannosaur prowled the Cretaceous landscape, ranging from the tiny, feathered Dilong to the almost T-rex-sized Albertosaurus. What these tyrannosaurs had in common was the same basic body plan: a bipedal posture, tiny arms, and big heads with sharp teeth.
2. Tyrannosaurus Sue is the world's most complete T. Rex skeleton.
In 1990, fossil hunter Sue Hendrickson discovered an 85-percent complete, full-grown T. Rex skeleton during an expedition in South Dakota. Legal troubles ensued, with the result that Tyrannosaurus Sue was auctioned off to the Field Museum of Natural History in Chicago for $8 million, a dinosaur fossil record.
3. T. Rex hatchlings may have been covered in feathers.
We all know that dinosaurs evolved into birds, and that some carnivorous dinosaurs (especially raptors) were covered in feathers. Some paleontologists believe that all tyrannosaurs, including T. Rex, must have been covered in feathers at some point during their life cycles, most likely when they first hatched out of their eggs.
4. Tyrannosaurus Rex had an incredibly powerful bite.
Back in 1996, a team of Stanford University scientists determined that T. Rex chomped on its prey with anywhere from 1,500 to 3,000 pounds of force, comparable to a modern alligator, and more recent studies put that figure in the 5,000-pound range. (For purposes of comparison, the average adult human can bite with a force of about 175 pounds). A bite that powerful may have been capable of shearing off a Triceratops' horns! (See this article for an analysis of who would win a battle between T. Rex and Triceratops.)
5. T. Rex also had very bad breath...
Granted, most dinosaurs didn't brush their teeth during the Mesozoic Era, and very few of them flossed. Some experts think the shards of rotten, bacteria-infested meat lodged in its numerous teeth gave T. Rex a "septic bite," which may have infected (and eventually killed) wounded prey.
6. ...not to mention a well-developed sense of smell.
Based on the size and shape of its olfactory lobes, T. Rex seems to have had a very sensitive nose, which would have helped it to hone in on living (or, more likely, already dead and rotting) prey. This is the reason some experts think T. Rex was an opportunistic scavenger rather than an active predator.
7. Female T. Rex were bigger than the males.
We don't yet know for sure, but there's good reason to believe (based on the size of existing fossils and the shapes of their hips) that female T. Rex outweighed their male counterparts by a few thousand pounds, a trait known as sexual dimorphism. Why? One reason may be that females of the species had to, well, lay clutches of T. Rex-sized eggs.
8. Tyrannosaurus Rex may have had a warm-blooded metabolism.
Some scientists believe that T. Rex (and other predatory dinosaurs) couldn't have maintained an active lifestyle with a cold-blooded metabolism. The evidence for "endothermy," as a warm-blooded metabolism is called, is slim, but it would help cement the evolutionary relationship between ancient dinosaurs and modern birds.
9. No one knows why T. Rex's arms were so short.
Did Tyrannosaurus Rex use its stunted arms to push itself off the ground after restful naps, or to clasp struggling prey close to its chest? Or is it possible that this predator's arms were completely useless, and would have disappeared entirely (as happened with snakes) after another few million years of evolution? No one has a clue, but this article discusses the issue further.
10. The average Tyrannosaurus Rex lived about 30 years.
It's hard to infer a dinosaur's life span from its fossil remains, but based on an analysis of existing fossils, experts speculate that adult T. Rex may have lived as long as 30 years--and since T. Rex was on top of the food chain, it was most likely felled by old age, disease, or hunger.