Unique structure of T. rex tooth helped rip apart larger animals

The ability of carnivorous theropods like the Tyrannosaurus rex to tear through the flesh and bone of their prey was due in part to a unique, deeply serrated tooth structure, according to new research published in the latest edition of the journal Scientific Reports.

In the study, Kirstin Brink, a post-doctoral researcher in the University of Toronto Mississauga Department of Biology, and her colleagues explained that sawlike structure of these dinosaurs’ teeth were found only on T. rex, Allosaurus, and even the early theropod species Coelophysis. While other creatures may have teeth that look similar, it was how the tissues inside the teeth were structured that made the teeth of theropods one-of-a-kind.

“In this study,” Dr. Brink told redOrbit via email, “we examined as many animals as possible with teeth that look similar to theropods: sharks, phytosaurs, crocodilians, sabre-tooth cats, the first known animals with serrated teeth, Dimetrodon (an ancient ancestor of mammals), and the only living animal with similar teeth, the Komodo Dragon.”

“These animals are all distantly related to each other,” she added. “Although these teeth look very similar from the outside, it is the unique structure of the tooth tissues inside the teeth that differentiate the dinosaurs from all these other animals. Only the theropod dinosaurs have the unique arrangement of dental tissues (different types of dentine, the tissue that makes up the majority of the tooth) that helps to strengthen and prolong the life of the tooth.”

So complicated

In addition to being stronger and longer-lived, the tissue arrangement in theropod teeth also improved their function, making them more efficient at chewing through bones and tearing the flesh of larger animals and reptiles, Dr. Brink and her co-authors from UTM, the Royal Ontario Museum and the National Synchrotron Radiation Research Center in Taiwan wrote.

“The fact that theropod teeth are quite more complex than previously thought was a surprise to me,” she explained. “Generally, dinosaurs that ate plants (duckbill dinosaurs and ceratopsians like Triceratops) have really complex teeth because the teeth wear away so quickly when grinding up tough plant material. Theropods generally ate much softer food (meat), so it was thought that their tooth structure wouldn’t need to be as complicated.”

“As reptiles (and dinosaurs) can continuously replace their teeth throughout their lives, if a theropod broke a tooth or wore through a tooth it could simply grow a new one. However, it can take up to two years for a new tooth to fully develop in T. rex,” Dr. Brink added. “Therefore, having a tooth with serrations that is strengthened by a special arrangement of tooth tissues can allow the tooth to function for longer periods of time without being worn down, which prevents gaps from occurring in the jaws where teeth are missing, thereby allowing for a more secure, efficient bite when piercing flesh.”

By examining samples of dinosaur teeth that had yet to break through the gums, as well as samples of mature dinosaur teeth, the study authors also found that the theropods’ unique tooth tissue arrangement did not develop as a result of chewing harder materials. They examined the tooth slices of eight carnivorous theropods using a device called a scanning electron microscope, which allowed them to understand the chemical composition of those teeth.

Despite the latest findings, Dr. Brink said that there is “still a lot we need to learn about reptile teeth. Most research on teeth is done on humans, but reptiles and mammals have very different tooth development. Reptiles can continuously replace their teeth, while pretty much all mammals cannot. Understanding the way reptile (and therefore dinosaur) teeth develop and function is a fruitful avenue for future research. Imagine if we could continuously regrow our teeth!”

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