A while back my family and I participated in a dinosaur dig in Moab led by BYU Paleontology professor Rodney D. Sheetz. The professor and his team had recently excavated a large sauropod very similar to an apatosaurus which is in the process of being named a separate species (moabosaurus.) The majority of the sauropods that he has found have been headless which has led him and his colleagues to speculate and theorize the method of predation. These animals were the titans of dinosaurs over 75 feet long and weighing perhaps as much as four elephants. The apex predators at the time were allosaurs, large and ferocious but diminutive when compared to the moabosaurus. The bodies of the moabosaurus were huge and tank-like complete with whiplash tails. Their most glaring weakness was their small diminutive heads.
Because of the lack of heads found in the digs the professor speculated that the allosaurs would target the head and in most successful cases the head of the sauropod would be ripped off which would explain the lack of skulls found with otherwise intact skeletons.