Ornithurae Ornithurae Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of "Ichthyornis", "Hesperornis", and all modern birds as well as all other descendants of that common ancestor. Ernst Haeckel coined the name in 1866 and included in the group all "true birds" with the "characteristic tail morphology of all extant birds" (translation by Jacques Gauthier). This distinguishes the group from "Archaeopteryx", which Haeckel placed in another new group called Sauriurae. Said simply, modern birds have short, fused pygostyle tails, while "Archaeopteryx" retained the long tail characteristic of non-avian theropod dinosaurs. Gauthier converted Ornithurae into
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