On Earth in prehistory, Ian Chesterton found an animal skull with no horns or antlers, suggesting that it came from a horse (TV: "The Cave of Skulls" [+]Part of An Unearthly Child, Anthony Coburn, adapted from The Pilot Episode (Anthony Coburn), Doctor Who season 1 (BBC tv, 1963).) or deer. (PROSE: Doctor Who and an Unearthly Child [+]Terrance Dicks, adapted from An Unearthly Child (Anthony Coburn), Target novelisations (Target Books, 1981).)