Beipaiosaurus was among the strangest of dinosaurs. It looked like a fusion of body parts taken from several other species and united in the unlikeliest of proportions. It had a stocky body, long arms adorned with massive claws, a long neck topped by an incongruously small head, and a beaked mouth. Bizarre as this cocktail of features is, it’s the animal skin that has currently warrants attention.
Fossils of Beipaiosaurus include impressions of its skin and these clearly show long, broad filaments clumped around its head, neck, rump and tail. They are feathers, but most unusual ones. Traces of feathers have been found on other dinosaurs (including the infamous Velociraptor) and they come in a variety of shapes and forms. But all are composite structures consisting of several slender filaments that either sprout from a single base or branch off a central stem.
Beipaiosaurus was also covered in some of these complex feathers, but it had other plumes that were far simpler. Each of these was a single, unbranched, hollow filament – exactly the sort of structure that palaeontologists had predicted as the first step in the evolution of feathers.
Until now, their existence was merely hypothetical – this is the first time that any have actually been found in a fossil. Other, more advanced stages in feather evolution have been described, so Beipaiosaurus provides the final piece in a series of structures that takes us from simple filaments to the more advanced feathers of other dinosaurs to the complex quills that keep modern birds aloft.