how does a dinosaur say merry christmas

Well, a dinosaur would probably say "Merry Christmas" in their own way, using their own dinosaur language. So instead of saying "Merry Christmas" they would say "Roar roar" or "Grrrrr" or something like that. It wouldn't be as clear or easy to understand, but it would still be their way of expressing their holiday greetings and good wishes for the season.