The evolution of modern birds (the fossil record) All birds have feathers except in prehistoric times. Knowledge of the ancient relatives of modern birds comes from fossil records. The first and most famous fossil with feathers is archaeopteryx found in bavaia in 1861. Size difference ad males long tail feathers show that sexual dimorphism may have existed in birds at least since that time. Advantages: colorful (social signaling), raise feathers up on head (defense or warning of enemy), insulation, camouflage. Skull was longer, had teeth, jawbone in p. Therapods laid eggs, had nests, and had feathers. Many had feathers, laid eggs in nests and anatomical features similar to birds. Fossils of a wide variety of aquatic birds. Loons, gulls, ducks, cranes, petrels: late cretaceous, eocene (60 mil years ago, miocene (20 mil years ago, late tertiary (10 mil years ago) Development of many of the modern species of birds. But for water birds: floating on ocean, sinks, covered by sandstone.