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Before a bird grows feathers or a mammal grows fur, its embryo must develop tiny, thickened spots that develop into feather or hair follicles. (These spots are called placodes.) Just as feathers and hairs are very different, so the way these placodes develop further into feather or hair follicles is very different. Reptile scales differ from both feathers and fur, and they develop in a way that is likewise very different from either. The dramatic differences between scales, feathers, and hair—whether in the developing embryo or in their mature form—have made it difficult to connect the evolutionary dots between reptiles, birds, and mammals.To finish reading, click on "Do Naked Bearded Dragons Reveal Common Ancestry of Scales, Feathers, and Fur?"
Evolutionists are convinced, however, that both birds and mammals evolved, though along separate paths, from reptiles. Therefore, they have searched diligently for a connection between the signature coverings of these three groups. Now evolutionary biologists Nicolas Di-Poï and Michel Milinkovitch believe they have found this scale-hair-feather connection in the previously undiscovered reptilian embryo’s placodes.