I have a way that doesn’t require dino gates but does require something else: Get 10 stone pillars, one stone ceiling, a stone stair, a flyer (pteranodon is preferable), darts and meat. Set 5 pillars in a U shape and double stack them and put ceiling on middle pillar. Lure Griffin into trap and place a stone stair behind so can’t move. Dart it and BOOM! You got a Griffin!