The early evolution of feathers: fossil evidence from Cretaceous amber of France. 2008. Vincent Perrichot et al. Proceedings of the Royal Society B. Tuesday, February 19, 2008.
Abstract: The developmental stages of feathers are of major importance in the evolution of body covering and the origin of avian flight. Until now, there were significant gaps in knowledge of early morphologies in theoretical stages of feathers as well as in palaeontological material. Here we report fossil evidence of an intermediate and critical stage in the incremental evolution of feathers which has been predicted by developmental theories but hitherto undocumented by evidence from both the recent and the fossil records.
Seven feathers have been found in an Early Cretaceous (Late Albian, ca 100Myr) amber of western France, which display a flattened shaft composed by the still distinct and incompletely fused bases of the barbs forming two irregular vanes. Considering their remarkably primitive features, and since recent discoveries have yielded feathers of modern type in some derived theropod dinosaurs, the Albian feathers from France might have been derived either from an early bird or from a non-avian dinosaur.
Watch the animated three-dimensional virtual reconstruction of one fossil feather from Early Cretaceous French amber in phase contrast microtomography showing vanes resulting from the opposed but irregular insertion of barbs on the flattened rachis HERE.