An illustration of a Gorgosaurus using its serrated teeth to rip apart its meal, a young Corythosaurus in Alberta, 75 million years ago. 
 
 Secret structures hidden within the serrated teeth of Tyrannosaurus rex and other theropods helped the fearsome dinosaurs tear apart their prey without chipping their pearly whites, a new study finds. 
 
 Researchers looked at the teeth of theropods — a group of bipedal, largely carnivorous dinosaurs that includes T. rex and Velociraptor — to study the mysterious structures that looked like cracks within each tooth. 
 
 The investigation showed that these structures weren't cracks at all, but deep folds within the tooth that strengthened each individual serration and helped prevent breakage when the dinosaur pierced through its prey, said study lead researcher Kirstin Brink, a postdoctoral researcher of biology at the University of Toronto Mississauga. [Image Gallery: The Life of T. Rex] 
 
 The new study upends one from the early 1990s, Brink said. Researchers first noticed these cryptic cracks on the tooth of a T. rex cousin named Albertosaurus about two decades ago. 
 
 Initially, the researchers thought the cracks were signs of damage, likely acquired when the dinosaur ate a hearty meal. But the new analysis finds that isn't the case, Brink said. 
 
 "I sectioned teeth from eight other theropods besides Albertosaurus, and found that the structure is actually in all theropods, and it's not actually a crack," she told Live Science. 
 
 This illustration shows a section of a tooth of the large theropod Gorgosaurus, from Alberta. Credit: Skull drawing by Danielle Default 
 
 Serrated teeth 
 
 The study actually began with a Dimetrodon, a Paleozoic animal with serrated teeth that lived before the time of the dinosaurs. When Brink sliced the Dimetrodon tooth in half and compared it with the serrated teeth of dinosaurs, she found they had different internal structures. 
 
 "They look very similar on the outside," Brink said. "It's only when you cut them open [that you see] that they're completely different." 
 
 Curious, she obtained two to three teeth from eight different theropods species, including T. rex, Coelophysis bauri and Carcharodontosaurus saharicus. She also looked at specimens of theropod teeth that had not yet fully matured and erupted past the gum line, meaning, "they had not been used for feeding," Brink said. 
 
 An analysis using a scanning electron microscope and a synchrotron (a microscope that helps determine the chemical composition of a substance) showed that each tooth, even the ones that had not yet erupted, had these cracklike structures next to each serration, she said. This debunked the idea that the cracks were artifacts of eating a meaty meal, she said. 
 
 Kirstin Brink, a postdoctoral researcher of biology at the University of Toronto Mississauga, shows a theropod tooth next to a cross section of a tooth belonging to the theropod Carcharodontosaurus. Credit: Image courtesy Kirstin Brink 
 
 Furthermore, each structure has a few extra layers of calcified tissue, called dentine, under the tooth's outer enamel coating, making it tough and hard. 
 
 "We proposed a developmental hypothesis that these are structures created when the tooth is first forming," Brink said. "It actually helps to deepen the serration within the tooth and strengthen each serration and the tooth overall." 
 
 Serrated teeth help animals pierce through flesh and hold onto chunks of meat. The formations, which the researchers call "deep interdental folds," strengthen the serrations. In fact, they likely helped theropods survive as top predators for about 165 million years, Brink said. 
 
 Serrated teeth still exist today in Komodo dragons. However, Komodo dragon teeth don't have deep interdental folds, nor do they have the extra layers of dentine that would strengthen their bite, Brink added. 
 
 She called the toothy finding fascinating and "unexpected." 
 
 "It's really cool that such a small, little change in the tooth structure, a small arrangement of the dental tissues, could completely change the ways these animals are living," she said. 
 
 The study was published online today (July 28) in the journal Scientific Reports. 
 
 Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science. ||||| Gorgosaurus -- one of the T. rex relatives studied -- is shown using its specialized teeth for feeding on a young Corythosaurus in Alberta, Canada, 75 million years ago. (Danielle Dufault) 
 
 As if Tyrannosaurus rex needed to get any cooler, new research suggests that the famous dinosaur had teeth that were serrated like a steak knife. These days, just one living terrestrial animal can boast such a magnificent mouth -- the komodo dragon. 
 
 But according to the new research published Tuesday in Scientific Reports, T. rex teeth stood in a class of their own. While lots of other dinosaurs (and the living komodo dragon) had teeth that seem similar to those in the jaw of a T. rex, researchers found that they were only superficially related. 
 
 [Dinosaurs aren’t really extinct] 
 
 The teeth of T. rex and its close relatives, it seems, were formed by a particularly complex structure of tissues. The building blocks that made their teeth and those of other dinosaurs were the same, but it appears that T. rex's kin, the theropods, had a better way of putting those blocks together. 
 
 
 
 Detail of a thin section through the tooth of a large theropod, Gorgosaurus, from Alberta. (Danielle Default) 
 
 The researchers investigated a small, crack-like feature at the bottom of the serrations -- a feature that can only be found when the tooth is cut open. It's not something you see in other animals with serrated teeth, and one previous study had suggested that the cracks were formed by use. In other words, they were stress cracks that formed when the dinosaurs chomped on hard bone, and their formation kept the whole tooth from shattering. 
 
 [Dinosaurs may have been warm-blooded after all] 
 
 But this new study suggests that theropod teeth had those "cracks" on purpose. By studying teeth that had yet to erupt (dinosaurs shed and produced teeth continuously throughout adulthood) in addition to ones that had been used for eating for awhile, the researchers found evidence that strange structures at the bottom of the serrations were there from the start. 
 
 [Why paleontologists love the noisy, featherless, inaccurate dinosaurs of ‘Jurassic Park’] 
 
 "The strange structure is actually a special arrangement of tooth tissues that increases the size of the serration, strengthening it and preventing it from wearing away quickly," lead study author Kristin Brink of the University of Toronto told The Post. "This means that teeth could last longer in the jaw, preventing gaps from occurring in the tooth row while a new tooth is developing, allowing for a more efficient bite when piercing through the flesh of its meal." 
 
 This hidden complexity, Brink said, no doubt helped the theropods find their success -- to the tune of about 165 million years at the very top of the food chain. 
 
 Read More: 
 
 Four-limbed, long-fingered snake hints at a creepy crawly evolutionary journey 
 
 Before dinosaurs, the giant ‘Carolina Butcher’ was a North American terror 
 
 A crummy dinosaur fossil turns out to hold 75 million-year-old blood and proteins 
 
 First ever evidence of a swimming, shark-eating dinosaur ||||| New research takes aim at the fanged portrayal of the T rex, suggesting enamel on its teeth was probably kept moist by thin, scaly lips much like those of lizards 
 
 Its image is one of a fierce predator who towered over most others, baring dozens of jagged, bone-crushing teeth. 
 
 But new research out of Toronto seeks to challenge depictions of the Tyrannosaurus rex, suggesting that its fearsome incisors might have been hidden behind a pair of lips. 
 
 “In popular culture, we imagine dinosaurs as more ferocious-looking, but that is not the case,” said Robert Reisz of the University of Toronto. In research presented Friday at a conference of the Canadian Society of Vertebrate Paleontology, he takes aim at the fanged portrayal of the T rex, suggesting its teeth did not stick out when its mouth was closed. 
 
 The truth of the tyrannosaurus - podcast Read more 
 
 The theory is based on the layer of thin enamel that covered the teeth of the T rex and fellow theropods. Reisz turned to modern-day reptiles to see how they keep this fragile enamel hydrated and protect their teeth from rotting. “If you have your teeth sticking out, you can’t hydrate the enamel. You can’t maintain it properly.” 
 
 Crocodiles get around this by spending time in water while monitor lizards have lips to protect the enamel on their teeth. Given that the T rex lived on land, the enamel on its teeth was probably kept moist by thin, scaly lips much like those of lizards. “People have a hard time wrapping their mind around the idea of teeth that are in excess of 10-15cm still being in the mouth,” Reisz said. “But it’s all a matter of some big-headed animals.” 
 
 The research is ongoing, but Reisz said most so far had welcomed the theory. He expected it to stir up some controversy among those responsible for depicting how dinosaurs might have looked millions of years ago, however. 
 
 The idea of lips on the T rex is not as far-fetched as it sounds, he said. Small theropods such as velociraptors are already often depicted with lips. It’s just the larger theropods, such as the T rex, who are almost always shown with their teeth exposed. 
 
 Still, he acknowledged that the theory might come as a blow to the dinosaur’s fierce image. “Maybe to children and a general audience they might look less ferocious without their teeth sticking out. But they are still big, impressive animals that were the top predators of their time.”
– The Komodo dragon is the only known creature on the planet today to boast teeth that are serrated, like a jagged-edged steak knife. But now researchers have discovered that the mighty T. rex not only sported serrated teeth, but also secret folds hidden toward the bottom of those teeth that both increased the size and strength of the serration and allowed the beast to shred the flesh of its prey, reports the Washington Post. "This means that teeth could last longer in the jaw, preventing gaps from occurring in the tooth row while a new tooth is developing, allowing for a more efficient bite when piercing through the flesh of its meal," says the lead author of the study, which appears this week in the journal Scientific Reports. Her team investigated the teeth of theropods, a group of primarily carnivorous and bipedal dinosaurs like T. rex and Velociraptor, to sort out why they were cracked at the bottom. It turns out the mysterious structures were deep folds that helped the mighty beasts tear apart their prey. (Previous theories suggested these structures were signs of wear and tear.) "The structure is actually in all theropods, and it's not actually a crack," the lead researcher tells LiveScience. "It's really cool that such a small, little change in the tooth structure, a small arrangement of the dental tissues, could completely change the ways these animals are living." (As if the teeth weren't enough, the T. rex's bite was likely the equivalent of this huge animal sitting on you.)