Feathered Fossil

From Xu, et al. 2009

The long and short filamentous fiber of Beipiaosaurus are quite clearly evident in the fossil remains. The downy layer of insulation feathering as hollow filaments are partially preserved in the fossil in the carbon film layer that halos the neck, tail, and hindlimbs especially. The longer, elongated broad filamentous fibers (EBFFs) make up a considerable amount of the halo and individual fibers are clearly visible within the halo. The length of the fibers is substantial, measuring between 100 and 150 mm (3-4 in) which is nearly half the length of the neck itself. These feathers are broad as well, of course, measuring up to 3 mm wide. The widest feather fibers in Sinosauropteryx, for comparison purposes are approximately 0.2 mm. This wider feather fiber allowed for the EBFFs of Beipiaosaurus to be a great deal more rigid than typical feathers. None of the fossilized fibers are bent or curved unnaturally or in a manner that indicates the shafts were coerced into their present positions by other forces. The rigidity of these feathers adds support to the hypothesis that these feathers would have been used as signalling or display structures rather than as air trapping insulatory structures as we find with the downy feathering layers.