Some birds possess an extensive rictus, creating a visual appearance that is akin to the mammalian cheek, though unaccompanied by buccinator-type musculature. What purpose does a large rictus serve, if it is not a cheek? Only parrots and Didunculus possess cheeks, on which grounds some authorities, formerly regarded Didunculus transitional

#rictus #birds #cheek #buccinators #ornithischians #oviraptorosaurs