Figure 1 in Dromaeosaurid crania demonstrate the progressive loss of facial pneumaticity in coelurosaurian dinosaurs

Figure 1. Craniofacial pneumaticity of Deinonychus. Maxilla YPM VP 5232 in (A, C) lateral and (B, D) medial views. Abbreviations: aofen, antorbital fenestra; aof, antorbital fossa; nepf, nasal exterior pneumatic foramina; mf, maxillary fenestra; na, nasal; pmf, promaxillary fenestra; mi, maxilla interior; ammf, anteromedial maxillary fenestra; mipf, interior maxillary pneumatic foramina; pmr, promaxillary recess; suas, suprantral strut; nipf, interior nasal pneumatic foramina; pras, preantral strut; mes, medial shelf; man, maxillary antrum; air, airway space; ear, epiantral recess; pmmf, posteromedial maxillary fenestra; rugose, rugose bone surface; smooth, smooth bone surface. In (C) and (D), light red are nasal pneumatic foramina, dark green is the maxillary fenestra, orange is the promaxillary fenestra, tan are maxillary pneumatic foramina, light green is the promaxillary recess, light blue is the anteromedial maxillary fenestra, pink is the epiantral recess, and red is the posteromedial maxillary recess. Courtesy of the Division of Vertebrate Paleontology, Peabody Museum of Natural History, Yale University, New Haven, CT, USA (peabody.yale.edu).