Most of the native cannibals in the movie were played by Brazilian military men on shore leave.
The actor Samuka, who played the native chief, actually had to eat a raw pig heart when he eats the heart of another character.
Massacre in Dinosaur Valley is also known as Cannibal Ferox II, although it shares little in common with the previous film except for the fact that they're both set in the jungle, feature white people pursued by cannibals, and fall into the nasty Italian films of the '70s and '80s. The alternate title was made by an English distribution company called VIPCO (Video Instant Picture Company). They associated the movie with the more notorious Die Rache der Kannibalen (1981) in order to sell more copies.
Most copies of Massacre in Dinosaur Valley have minutes cut from their runtime because of multiple gratuitous scenes. All of them have to do with nudity in some way, though: sex scenes and graphic shots of kempt vaginas are really all that's been edited from the film, and the cuts don't have any effect on the film whatsoever.