Dorsal view of MVZ 43325. The osteological characters diagnosing an Opisthocomidae + Cariamidae + Cuculidae + Musophagidae clade include an ulna that does not distinctly exceed the humerus in length, a dorsoventrally wide and strongly ventrally deflected proximal end of the os metacarpale on the carpometacarpus, and a deeply excavated recessus caudalis fossae on the pelvis (Mayr and Clarke, 2003).