In the battle between a predator and an alien, when the predator net-captures the alien and wants to kill it with its knife, the alien cuts the net and pounces on the predator and kills it with its piercing tongue. In the piercing shot you can clearly see that the predator's skull is fractured by the alien's tongue and some green blood gushes out from the hole. But in the next shot (almost two seconds later!), now taken from the predator's overhead angle, predator's skull is completely intact with no hole in it or blood on it!!!