Feather a dromaeosaurid found in the Yixian formation (124.6 MYA). Previously, a temporal paradox existed in the evolution of feathers—theropods with highly derived bird-like characteristics occurred at a later time than "Archaeopteryx"—suggesting that the descendants of birds arose before the ancestor. However, the discovery of "Anchiornis huxleyi" in the Late Jurassic Tiaojishan Formation (160 MYA) in western Liaoning in 2009 resolved this paradox. By predating "Archaeopteryx", "Anchiornis" proves the existence of a modernly feathered theropod ancestor, providing insight into the dinosaur-bird transition. The specimen shows distribution of large pennaceous feathers on the forelimbs and tail, implying that pennaceous feathers spread to
Specimens of Archaeopteryx "Archaeopteryx" likely indicated it had very little flight ability. The furcula (wishbone) is well-preserved and lies between the scapulae; its boomerang-like shape reveals a 75-degree angle between its branches. De Beer identified a compressed mass of bone as a sternum in the London specimen, but later researchers disputed this as more likely to be a concretion of vertebrae encrusted by calcite. That "Archaeopteryx" lacked a bony sternum is in agreement with the modern consensus that many specimens of "Archaeopteryx", including the London, likely represented immature animals whose sterna were still cartilaginous. The pelvic girdle is separated into its three components