This is from the 2005 Annual Review of Earth and Planetary Sciences: “Feathered Dinosaurs“.
Recent fossil discoveries from Early Cretaceous rocks of Liaoning Province, China, have provided a wealth of spectacular specimens. Included in these are the remains of several different kinds of small theropod dinosaurs, many of which are extremely closely related to modern birds. Unique preservation conditions allowed soft tissues of some of these specimens to be preserved. Many dinosaur specimens that preserve feathers and other types of integumentary coverings have been recovered. These fossils show a progression of integumentary types from simple fibers to feathers of modern aspect. The distribution of these features on the bodies of these animals is surprising in that some show large tail plumes, whereas others show the presence of wing-like structures on both fore and hind limbs. The phylogenetic distribution of feather types is highly congruent with models of feather evolution developed from developmental biology.
Annual Review of Earth and Planetary Sciences
Vol. 33: 277-299 (Volume publication date May 2005)
First published online as a Review in Advance on January 7, 2005
Mark A. Norell and Xing Xu