I’m not entirely sure if this theory can be considered canon, but I think that the ammonite uses the pheromones as a psychological convincer to any random creature to defend it.
That’s just a theory, a GAME THEORY!!!
Ever met a cry baby?..This guy will wail if you hit it and will cover you in a type of pheromone gas....causing you to attract every dino, sea or land, to bite your butt. Prepare for war. You only need to survive 80sec.