One might expect a fearsome carnivore like Tyrannosaurus to have the most teeth in the dinosaur kingdom, but the prize for the toothiest grin goes to Nigersaurus, an odd-looking herbivore with a staggering dental arsenal: over 500 teeth packed into its unusually shaped jaws.
What kind of dinosaur was Nigersaurus?
Measuring about 30 feet from head to tail, Nigersaurus was an elephant-sized herbivore that lived during the Mesozoic Era, around 110 million years ago—more than 40 million years before Tyrannosaurus existed. Its fossilized remains were first discovered in the Sahara Desert of Niger in the late 1990s by paleontologist Paul Sereno, who gave the creature its name in honor of the country where it was unearthed.
During the Mesozoic, Niger was a lush rainforest where herbivores like the long-necked Nigersaurus and sail-backed Ouranosaurus grazed on low-growing plants. Compared to its sauropod relatives—giant, four-legged dinosaurs known for their long necks and small heads—Nigersaurus was relatively small. While a Brachiosaurus could exceed 100 feet in length and weigh over 50 tons, an adult Nigersaurus tipped the scales at about two tons.
Sereno called the Nigersaurus “the weirdest dinosaur that I’ve ever seen,” largely because of its vacuum-shaped, box-like head. Even stranger, each jaw was lined with rows and rows of thin, replaceable teeth numbering in the hundreds.
Why did Nigersaurus need so many teeth?
Unlike the much larger Brachiosaurus, which munched on the leaves and branches of tall trees, Nigersaurus spent most of its life with its Hoover-shaped head facing downward, grazing on ground-level plants with its wide jaws. That’s why Sereno dubbed Nigersaurus the “Mesozoic cow.”
Prehistoric plants like horsetail contain crystals of silica, which can grind away at an herbivore’s teeth. That’s why evolution equipped Nigersaurus with an ingenious system for replacing its teeth quickly and continuously.
The upper and lower jaws of the Nigersaurus operated like conveyor belts. Each jaw contained roughly 60 active teeth in the front. But behind each active tooth were columns of five to 10 replacement teeth lined up and ready to go. In total, Nigersaurus carried more than 500 teeth in its mouth, far more than any other dinosaur. The runners-up were duck-billed hadrosaurs—herbivores of the late Cretaceous period—whose mouths were lined with stacks of 300 teeth for grinding tough plant material.
Sereno described the grazing style of the Nigersaurus as “nipping” rather than “chomping or chewing.” The teeth of the upper and lower jaws slid past one another in a shearing action, increasing the wear and tear on each tooth. Sereno calculated that Nigersaurus replaced its active teeth every four weeks, twice as quickly as hadrosaurs.
