The results of that research helped in solving a very old puzzle in biology. In a study published in the journal Science Advances on Friday, Milinkovitch and his grad student, Nicolas Di-Po, report that the mutated gene which robbed the bearded dragon of its scales is the same gene which is responsible for development of feathers in birds and fur in mammals. The researchers said that the three features look very different in adult animals, they start in the same place.
"It's interesting, because these are really key features that allow us to recognize lineages," Milinkovitch said. "How do you recognize birds? Because they have feathers. And mammals have fur, and reptiles have scales."
Milinkovitch noted that these differences might look like fundamental differences, but really they are fundamentally the same. "They're all inherited from a common structure that then diverged hugely," Milinkovitch said.
The scientists are mystified by the current diversity of feathers, fur and scales. They are still looking for any other intermediate forms to illustrate how they might be related to one another but in vain. It is mainly because the features are so fragile - while bone and teeth can be preserved as fossils, delicate skin appendages get lost with the passage of time.
"Either the placode was ancestral for everyone and then it was lost multiple times in independent lineages of reptile . . . or birds and mammals invented placodes independently," said the researcher.