That mandible shown in the photo with the police officer holding it is NOT a triceratops. Nor is it any other type of dinosaur. What appears in the photograph is clearly the mandible of a proboscidean, a relative of current elephants. During the Pleistocene (Ice Ages) some of them moved into South America.

Don’t take my word for it; check with any university or museum vertebrate paleontologist (not archeologist, please, since that is a different discipline though some will cover hunting of elephant relatives, too, and will recognize it that way) on your resources list.

That said, fossils, like archeological specimens, need to be respected, collected properly with full data, and studied when possible and appropriate.