English: Main structures of central nervous system (including optic tectum) and inner ear (vestibular system and cochlear duct) across selected birds (extinct and extant) and closely related non-avian dinosaurs. While the orientation of the foramen magnum varies across phylogeny, the degree of ventralization of the foramen magnum in MPM-334-1 is significantly greater than that of other stem taxa, and comparable to that of certain crown birds (e.g. Accipiter and Selasphorus). Stem-based and node-based clade names are explicitly illustrated. Illustrations are not scaled.