Enantiornithes

                These forms are considered "opposite birds" because of the bone
                structure of the scapula (shoulder blade) and coracoid (a small bone
                connected to the scapula).  These bones are oriented opposite of
                of those in modern birds.  Fossils indicate that these birds ranged
                in size from a few inches up to a few meters.

                Enantiornithine birds were widely distributed during the Cretaceous
                era.  Fossils have been located in Argentina (Walker 1981), North
                America (Hutchison 1993), Mexico (Brodkorb 1976), Mongolia
                (Elzanowski 1981), Australia, and Spain.