Never ever ever take one of these guys on with a pteranadon even if your friend tells you to. These Dino's can knock you off your mount and stun you for ten seconds, this is no dillo blinding attack when stunned you cannot do anything at all except watch him eat you and your dino.
For the love of god, do not fight them in water! A level 4 baryonx nearly killed my Theri because the baryonx had stunned him. No matter how shallow the water is, do not even think about fighting one. They can stun you and knock you off your creature.