The beloved three-horned dinosaur had teeth that were surprisingly complex—more so than many modern reptiles, even rivaling the complexity of mammal teeth. By having chompers that strategically wear themselves down with use, a Triceratops ends up with knife-like teeth that can finely slice through dense plant material. This allowed the master masticators to enjoy a richer, more varied diet. The findings were published in Science Advances this week.
The pointy teeth of modern-day reptiles are made for seizing and crushing food. They don’t chew, and their teeth don’t come together (or occlude) like ours. With herbivorous mammals, a process called self-wear actually changes the shape of the teeth to adapt to chewing certain kinds of food. This can create intricate file surfaces useful for mincing up plants, for example. "It's just been assumed that dinosaurs didn't do things like mammals, but in some ways, they're actually more complex," Florida State University’s Gregory Erickson says in a news release. But previous work revealed how duck-billed dinosaurs had complex teeth, and researchers suspected the same was true for horned dinosaurs.
To investigate, a team led by Erickson and Lehigh University’s Brandon Krick gathered up 66-million-year-old Triceratops teeth from museums, sliced them up, and studied how their surfaces interact while in motion. To their surprise, the material properties of the fossils were remarkably preserved: "If you took these dinosaurs' teeth and put them in a cow for example, they would work," Erickson says.
After cutting up some of the specimens, the team discovered that the Triceratops teeth were composed of five different layers of dental tissue. For comparison, crocodiles and other reptiles have just two layers in their teeth (enamel surrounding a softer core), while horse and bison teeth, once considered the most complex ever to evolve, have four.
Meanwhile, to simulate the wear process during dino chewing, the team slid a diamond-tipped microprobe across the fossilized teeth. By mimicking how plants moved across the teeth, they were able to measure the tissue wear rates. They discovered that, like mammals, Triceratops teeth self-wear: Their functional teeth strategically wore down with use to create vertical slicing faces (see image at the top).
With the help of 3D modeling, the team found that each of the five tissues played a specific biomechanical role in this tooth-wearing process. The high wear rate of one of them, for example, makes it possible for bowled-out central regions to change over time. These recessed areas in the middle—called fullers, like the grooves in the center of blades on swords and chef knives—reduced the area between the tooth and the plant being chewed. This cuts down on friction during biting to improve feeding efficiency.
The findings may explain how Triceratops adapted to exploit new diets and dominate among the plant-eating giants. The team plans to examine more dental records to see how prevalent these complex teeth structures were among dinosaurs.
Images: Erickson et al. Sci. Adv. 2015;1:e1500055 (top), Bill Lax/Florida State University (middle)
