But the odd thing about the skull was one, had teeth, and the other had a beak. Scientists thought it was of two distinct species. However, after a bit more investigation, they noticed that the fossils were identical except the teeth.
They later discovered that the teeth belonged to a much younger Limusaurus inextricabilis. This led them to conclude that the young had teeth. This is an adaptive character, not seen in any animal during that time. Today it is present is some animals like fish.
"Initially, we believed that we found two different ceratosaurian dinosaurs from the Wucaiwan area, one toothed and the other toothless, and we even started to describe them separately," said Shuo Wang of Capital Normal University in Beijing, China, who led the research. "Up until now, who would have thought that there were dinosaurs that had teeth as babies, started to lose them as they grew up and then ended up as toothless adults with beaks?"
The scientist says that he believed that the young had the teeth because they were omnivorous. The rapacious nature gave them a chance to survive as they offered them a wider range of foods. As they grow up, they better adapted to plants as they lost their teeth and formed a beak.