facet. The vertebral bodies of the front half of the synsacrum were excavated at their sides, comparable to the back vertebrae. Robust side processes connected the synsacrum to the ilia of the pelvis. Although earlier descriptions had counted four or five "free", not fused, tail vertebrae, Chiappe e.a. in 1999 reported seven of them. These had round and somewhat concave front articulation facets. Their spinal processes were high and transversely compressed. The side processes were robust and stick out horizontally to the side. Their articulation processes were rather long. The last of these vertebrae had a rectangular profile. Its neural arch had short processes pointing obliquely to above and sideways. The tail ended in a pygostyle, a complete fusion of the last vertebrae. Their number is uncertain. The pygostyle was about 40% longer than the first part of the tail. At its underside the pygostyle bore a well-developed keel, running from front to rear. Its top was incised by a long groove between prominent ridges. Confuciusornis had an exceptionally large humerus (upper arm bone). Near its shoulder-end this was equipped with a prominent deltopectoral crest. Characteristically this crista deltopectoralis was with Confuciusornis pierced by an oval hole which may have reduced the bone's weight or enlarged the attachment area of the flight muscles. The furcula or wishbone, like that of Archaeopteryx, was a simple curved bar lacking a pointed process at the back, a hypocleidum. The sternum was relatively broad and had a low keel which was raised at the back end. This bony keel may or may not have anchored a larger, cartilaginous, keel for enlarged pectoral muscles. The scapulae (shoulder blades) were fused to the strut-like coracoid bones and may have formed a solid base for the attachment of wing muscles. The orientation of the shoulder joint was sideways, instead of angled upward as in modern birds; this means that Confuciusornis was unable to lift its wings high above its back. According to a study by Phil Senter in 2006, the joint was even pointed largely downwards meaning that the humerus could not be lifted above the horizontal. This would make Confuciusornis incapable of the upstroke required for flapping flight; the same would have been true for Archaeopteryx. The wrist of Confuciusornis shows fusion, forming a carpometacarpus. The second and third metacarpals were also partially fused, but the first was unfused, and the fingers could freely move relative