Figuring Out Feathers
Feathers turn out to be surprisingly complicated. First, there's the question of which animals have feathers. For centuries, people thought feathers were unique to birds. Now we know this isn't true. In the last several years, paleontologists have found feathers on various species of extinct dinosaurs. So when did feathers first appear? And how did they evolve? Scientists continue to investigate these questions.
Like all complex biological features, feathers evolved in stages. Fossil discoveries from Liaoning support this idea. Some of the Liaoning dinosaurs had very simple feathers, while others had more advanced ones, similar to those found on modern birds. The evolution of feathers dates back more than 150 million years.
Species: Caudipteryx zoui
Birdlike dinosaur with feathers covering whole body. Long, striped tail plume.
The feathers on Caudipteryx are very similar to those of modern birds. The feathers have a central hollow shaft with numerous thin filaments (called barbs) extending outward, creating the recognizable shape of a feather. Yet even though Caudipteryx had feathers like modern birds, it did not fly because its arms were too short. Modern feathers evolved long before the ability to fly.
Species: Microraptor gui
Birdlike dinosaur; feathers on hind limbs give appearance of four wings.
Microraptor's feathers are essentially identical to those of flying birds today. Yet scientists aren't certain whether this dinosaur could fly. Some researchers have suggested that Microraptor may have glided from tree to tree, much like a flying squirrel.
Evolution of Feathers
Modern feathers consist of hundreds of thin fibers extending from a hollow shaft that runs the length of the feather. At the tip of each fiber are numerous tiny, hook-shaped structures that work like Velcro™ to hold the feather together. This complicated structure evolved in multiple stages over many millions of years.
- STAGE ONE: thin, hollow filaments appeared over 150 million years ago.
- STAGE TWO: tufts of filaments that somewhat resemble down feathers.
- STAGE THREE: numerous filaments sticking out from a central shaft.
- STAGE FOUR: shaft located off-center; these feathers provide the aerodynamic lift needed for flight.