Here's what rhymes with prototherians.
                        
                        
                    
                                proletarians  agrarians  clarions  barbarians  librarians  vegetarians  libertarians  sectarians  vulgarians  antiquarians  seminarians  utilitarians  veterinarians  centenarians  authoritarians  sanitarians  totalitarians  cnidarians  egalitarians  octogenarians  nonagenarians  humanitarians  disciplinarians  latitudinarians  septuagenarians  valetudinarians  sexagenarians  parliamentarians  Words that almost rhyme with prototherians
variance  chameleons  covariance  invariance  aquariums  honorariums  vivariums  planetariums  sanitariums  burials  thespians  decennials  lesbians  pedestrians  hairpieces  perennials  biennials  poinsettias  reburials  wistarias  triennials  antimalarials  equestrians  terrestrials  centennials  conventicles  bicentennials  centrepieces  extraterrestrials  sesquicentennials