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More research reveals why birds are toothless

Researchers over at the George Washington University have discovered a new species of toothless dinosaurs which could explain the reason why birds have beaks.

The dinosaur they observed was  Limusaurus inextricabilis, which forms part of the theropod group of dinosaurs, which are evolutionary ancestors of birds. These dinosaurs lost their teeth during their adolescent phase and didn’t grow another set when they got older.

James Clark, a Ronald Weintraub Professor of Biology at the George Washington University’s Columbian College of Arts and Sciences, was a co-author of the paper, published in Current Biology.

The team studied 19 Limusaurus skeletons which were discovered in the Xinjiang province of China in ancient death traps where they got stuck in thick mud and died. Their samples ranged from baby Limusaurus specimens to adult ones who expressed a pattern of tooth loss over time. Researchers found that the young skeletons had small, sharp teeth while the adults were consistently toothless.

“This discovery is important for two reasons. 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,” said Clark in a press release.

New research suggests why birds today are toothless

The team also noted in their research the species’ hand development and found that their reduced first finger could possibly have been transitional.  They also found that later on, theropods lost their first and fifth fingers and that bird hands consisted of identical human second, third and fourth fingers.

These fossils indicated that younger Limusauruses might have been carnivores or omnivores due to their small teeth while the adults who lost their teeth could’ve been herbivores. The chemical makeup in their bones also supports the theory that there was a change in diet between younger and older Limusaurus.

These fossils help show how some theropods such as birds lost their teeth, due to their ageing from babies to adults.

“For most dinosaur species we have few specimens and a very incomplete understanding of their developmental biology,” said Josef Stiegler, a GW graduate student and co-author of the paper. “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,” he continued.

Featured image: Tina Lawson via Flickr