Feathers and 'feather-like' integumentary structures in Liaoning birds and dinosaurs

We provide an overview of the known feather and other ‘feather-like’ integumentary structure types known to-date in the birds and dinosaurs from the Cretaceous rocks of Liaoning, NE China. These feather-types are classified and compared with similar structures seen in Mesozoic and extant birds. We consider that integumentary feathers and ‘feather-like’ structures fall within two major structural categories (‘shafted’ and ‘non-shafted’). Comments are also made on the possible aerodynamic or insulating function of leg and tail feathers in Mesozoic birds and theropods.