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No toothbrush required: Dinosaurs replaced their smile every month.

Sauropod dinosaurs, an order of vertebrate herbivores, had multiple reserve teeth in their tooth sockets to continuously replace failing teeth.

By Contributor / August 6, 2013

Visitors walk past a dinosaur mock-up of a Diplodocus reflected in the water at the Dinosaur Park in Kleinwelka near Bautzen, eastern Germany in 2013. New research has shown that Diplodocus replaced its little teeth about once a month.

Jens Meyer/AP


Selling a toothbrush to a dinosaur would be a hard pitch.

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A team of paleontologists found that gigantic “long-neck” herbivores packed up to nine reserve teeth in each tooth socket, regularly replacing their dulling teeth with fresh ones. That strategic tooth-replacement broadens the portrait of how the lumbering giants evolved and adapted to their ecosystem.

Adult sauropod dinosaurs, an order of vertebrate herbivores, had the largest body sizes of any terrestrial animal, reaching lengths of up to 100 feet. Sustaining that gargantuan bulk required an enormous amount of food, and the dinosaur’s teeth underwent significant abrasion from the constant eating.

So, over about 300 million years, those dinosaurs had to evolve some helpful dental infrastructure that would allow them to cope with the wear and tear.

“Sauropods have very simple teeth, so people have often thought of those dinosaurs as very basic and not very interesting,” said John Whitlock, a paleontologist at Carnegie Museum of Natural History and a lead author on the research, published in PLOS ONE. “But it turns out that those simple teeth are tied into this remarkable teeth replacement and adaptation.”

It has been known since at least the 1890s that most non-mammals, both modern and extinct, regularly exchange their teeth. That phenomenon has been well studied in several species of dinosaurs – including the T.rex, which shuffles its old teeth out about once a year – but the rate at which large herbivores replace their teeth had not been researched. 

To better understand these huge animals’ dental scheme, researchers sectioned two Jurassic period sauropod jaws: one from a Camarasaurus, dug up in southern Utah, and the other from a Diplodocus, recovered in Colorado. Both sauropods lived some 150 million years ago in Laramidia, the densely populated island landmass that is the now the western North and South American spine. 

CT scans were first taken of both jaws at the University of Michigan health center. The scientists then sectioned those jaws, removing not only the visible teeth, but also the backup teeth embedded behind them.

To determine how fast those replacement teeth were grown in, the scientists then looked at the dentin – the layer beneath the tooth enamel – in the dinosaurs’ current teeth. A new layer of dentin is added each day, and the resulting layers can be counted to show age, much as growth rings in a fish’s earbones reveal how many seasons the animal has weathered. The age of the current teeth was compared to the backup teeth to determine the rate at which the new teeth would have grown in.


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