Out of the Blue
Kill 20 humans with a Pteranodon peck while flying.


Note: The achievement can be easily earned in a private server with your friend.

1. Pick Pteranodon and hit the human 2 times (so you can kill him with 1 peck only later).
2. Human will then kill you and start looking into ground (so there is no chance he can see you).
3. Pick Pteranodon again and kill the human with your peck while flying.
4. Repeat the above 3 steps until you get the achievement.

Note: It's important the Pteranodon to not be seen in human's screen.

Credit for the method goes to SC4LDER.