Axial and appendicular pneumaticity in Archaeopteryx

From the time of its discovery in 1860 to this day Archaeopteryx has been e ssential to our understanding of avian evolution. Despite the great diversi ty of plesiomorphic avialan (sensu Gauthier 1986) taxa discovered within th e last decade, Archaeopteryx remains the most basal avialan taxon. A very u nusual feature of extant birds is their lung structure, in which air divert iculae penetrate the bones. This has previously been reported in Archaeopte ryx as well, in the cervical vertebrae of the Berlin specimen and in an ant erior thoracal vertebra of the Eichstatt specimen. This indicates the prese nce of a cervical air sac. We show that the London specimen also has pneuma tized anterior thoracal vertebrae, and, thus, that this feature was present in the most archaic avialans, as the London and Eichstatt specimens are di fferent species. Furthermore, the pelvis of the London specimen shows clear signs of the presence of an abdominal air sac, indicating that at least tw o of the five air sacs present in modem birds were also present in Archaeop teryx. Evidence of pubic pneumaticity was also found in the same position i n some extant ratites.