Ornithothoraces

Ornithothoraces is a group of avialans that includes all enantiornithines ("opposite birds") and the euornithes ("true birds"), which contains modern birds and their ancestors. The name Ornithothoraces means "bird thoraxes". This refers to the modern, highly advanced anatomy of the thorax that gave the ornithothoracines superior flight capability compared to more primitive avialans. This anatomy includes a large, keeled breastbone, elongated coracoids and a modified glenoid joint in the shoulder, and a semi-rigid rib cage.