Percival Lowell
Literature and science fiction have created a wealth of gentilics that are not directly associated with a cultural group. These will typically be formed using the standard models above. Examples include "Martian" for hypothetical people of Mars (credited to scientist Percival Lowell), "Gondorian" for the people of Tolkien's fictional land of Gondor, and "Atlantean" for Plato's island Atlantis.