Dinosaur Lost Teeth in Adolescence

A dinosaurs species has teeth as babies only to lose them as teenagers, says a new study published in Current Biology.

The Limusaurus lost its teeth at adolescence, and lived without a new set of teeth in adulthood. Photo credits: George Washington University.

Dinosaurs, Birds, & Teeth

Dinosaur Limusaurus not needing its teeth as it grows may explain why birds don’t have teeth. A team of researchers examined 19 skeletons of the dinosaur species named Limusaurus inextricabilis, and found that the animal did not have permanent teeth because once it lost its baby teeth in adolescence, it did not grow more teeth back in adulthood. These findings constitute a tremendous anatomical change, and might be used to understand why birds have beaks instead of teeth because L. inextricabilis happen to be considered the evolutionary ancestors of birds.

Sharp-Teethed Babies & Toothless Adults

The bones were spotted in China’s Xinjiang Province, where the animals are said to have died after getting stuck in the mud. The dinosaurs were of varying age groups, from baby to adult—a rare finding, and this allowed the researchers to view a pattern in terms of the presence and absence of teeth: baby skeletons demonstrated small and sharp teeth while the older ones were all toothless.

“This discovery is important for two reasons,” says one of the authors, James Clark, from George Washington University’s Columbian College of Arts and Sciences. “First, it’s very rare to find a growth series from baby to adult dinosaurs. Second, this unusually dramatic change in anatomy suggests there was a big shift in Limusaurus’ diet from adolescence to adulthood.”

Carnivore Babies & Herbivore Adults

This would mean that baby Limusaurus were possibly omnivores or carnivores while their older counterparts would have been herbivores. This hypothesis is not only supported by the teeth-to-no-teeth pattern, but also by the chemical composition of the bones that suggests a shift in diet.

The results can also be used to explain how theropods (a group including birds) lost their teeth, in terms of changes that occurred from their early years to adulthood.

“The large sample size of Limusaurus allowed us to use several lines of evidence including the morphology, microstructure and stable isotopic composition of the fossil bones to understand developmental and dietary changes in this animal,” says co-author Josef Stiegler, also from the George Washington University.

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