Diictodon was a very common type of herbivore from the late Permian Period (about 255 million years ago). Predating the dinosaurs, this burrowing creature is an evolutionary link between mammals and reptiles. (It is classified as a “mammal-like reptile.”) The physical depiction on ‘Primeval’ is fairly accurate, if a bit on the large side. Scientists unearthed complete fossils in Africa and Asia—in fact, the Diictodon accounts for roughly half of all Permian vertebrates found in South Africa.