Magazine article Science News

Teeth Offer a Taste of Ancient Lifestyles

Magazine article Science News

Teeth Offer a Taste of Ancient Lifestyles

Article excerpt

Teeth can't talk, but they can tell a visual tale about how the dinosaurs and other ancient animals lived, say paleontologists who have devised two ways to study long-extinct creatures by probing their dental details.

By looking inside fossilized reptile teeth, one scientist has developed a process that may help in estimating dinosaur populations. Another researcher has examined the outside of mammal teeth to help decipher the eating habits of ancestral primates. The two described their work last week in separate talks at the annual meeting of the Society of Vertebrate Paleontology, held in San Diego.

Gregory M. Erickson of the Museum of the Rockies in Bozeman, Mont., studied dental growth lines visible inside the fossilized teeth of dinosaurs. Using living alligators as an analog, he demonstrated that each line in the fossil tooth corresponds to one day of growth - enabling researchers to determine how long it took different dinosaurs to develop their teeth.

To make his case, Erickson injected tooth-staining tetracycline into live alligators, which were raised at a commercial farm and later killed for their skins. Examining a cross section of each tooth under a scanning electron microscope, he then located the tetracycline stain and counted the growth rings that had developed since the injection. The number of rings matched the number of days between injection and slaughter, proving the teeth grew a ring each day. Because dental rings in fossil alligators and dinosaurs resemble those in live reptiles, Erickson reasoned that the rings inside dinosaur teeth also represent daily growth.

Such information can reveal how often a dinosaur shed its teeth, he says. Erickson found that plant-eating hadrosaurs went through their teeth rapidly, replacing each after two to three months, whereas the knife-like teeth of the carnivorous Tyrannosaurus rex lasted 2 1/2 to three years before failing out. …

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