There were several species of dinosaurs – some were covered by feathers while others were not. Birds are the only existing animals that share ancestry with dinosaurs. Research has shown that a majority of the dinosaurs that had feathers were theropods. They include tyrannosaurs, raptors, "dino-birds," ornithomimids, Herrerasaurus, and Eoraptor. However, not all theropods had feathers; some including Tyrannosaurus Rex and Spinosaurus had scaly skin. Until the late 1990s, no observational or recorded research proved or disproved the existence of feathered dinosaurs.
The Evolution Of The Feathered Dinosaurs
In 1859, Charles Darwin published On the Origin of Species documenting the theory of evolution. By then several remains of dinosaurs had been discovered, but no researcher had linked the giants to any existing species of animal. After reading Darwin's work, British researcher Thomas Henry Huxley suggested that birds are the living descendants of dinosaurs. Huxley based his theory on the resemblance of the skeletal structures of a small dinosaur and birds. The idea was dismissed and put to rest by other scientists. A century later, American paleontologist John Ostrom discovered the remains of a theropod and noted that it resembled that of birds. Ostrom suggested that birds and dinosaurs could actually be related. After several discoveries of theropods, scientists agreed that the two species were positively correlated. Some even went further to claim that dinosaurs may have been feathered, but no discovery backed up the theory. Not all researchers were convinced by the idea of feathered dinosaurs.
In the late 20th century, the fossils of feathered dinosaurs were discovered. However, they were all remains of small dinosaurs that resemble more birds than the ancient dinosaurs. In 1996, a large feathered Sinosauropteryx was found in China. The discovery marked a turning point in how researchers reviewed and presented the dinosaurs. Since then, thousands of fossils supporting the presence of feathers among some dinosaurs have been dug up. Unlike birds, the feathers of large dinosaurs did not evolve to support flight. Instead, the feathers served as insulation, and for visual display.
The Evolutionary Advantage Of Feathers
By observing modern birds, one might conclude that the primary function of feathers is to support flight. The line of thought is logical because only feathered birds fly. However, not all feathered birds fly. Some birds such as the domestic chicken, penguins, and ostriches do not fly, yet they possess feathers. Research has shown that flight is a complex evolutionary process that stretches beyond features. The core purpose of feathers is insulation; they protect the skin of birds from external damage and extreme weather conditions.