Modern birds are living dinosaurs, having evolved from a line of theropod dinosaurs more than 150 million years ago. According to fossil evidence, some dinosaurs from long ago even had feathers—or structures that had various aspects of modern bird feathers before birds evolved. In the mid-1990s Sinosauropteryx, a dinosaur fossil dating to the early Cretaceous Period (about 126 million years ago), was revealed at a scientific conference. This animal was exceptional because, even though it was a dinosaur, its head, neck, back, and tail were covered with a thick short “pelage” of dark filaments. These filaments were certainly epidermal, and, judging by their straightness and evident stiffness, they were probably composed of keratin and other proteins. What’s more, some of them appear to have been branched.
Since the mid-1990s other dinosaur fossils—some older than Sinosauropteryx—have been discovered that show evidence of feathers. These fossils indicate that some individual feathers had simple branched filaments whereas other feathers had a strong fused base and a tuft of filaments, slightly similar to the downy feathers of modern birds. Still other feathers were gathered in vanes with a rudimentary stalk and a strong base. Archaeopteryx, a genus of feathered dinosaur that was once thought to be the oldest fossil bird, is probably the best-known example of a dinosaur with feathers. It lived during the late Jurassic Period (163.5 million to 145 million years ago). However, the earliest fossil bird known to be ancestral to the lineage of modern birds is Archaeornithura meemannae, which dates to 130.7 million years ago.