1. get behiind a mutant
2. hit it using 1,2, and 3 attacks. it will get his attention
3. make him come to you, then hit 4. this is the strongest attack.
4. while recharging, make sure to stay away from the mutant, but not to the point where he dosent chase you anymore. or you can pounce him using left alt while waiting for the 4 button to recharge. make sure not to get too close.
5. repeat steps 3-4 until it dies

trust me. i unlocked 3 dinos using this method.