Ape-Men of Xlotli – Astounding Stories Clayton Cover, c.1930

In an era gripped by Darwinian anxieties and lost-world fantasies inspired by Conan Doyle and Edgar Rice Burroughs, this visceral cover captures the pulp id at full throttle. A square-jawed hero in a red shirt raises a wooden club against a snarling, red-eyed ape-man while a terrified blonde woman recoils behind him, surrounded by a horde of simian creatures in a subterranean gloom — civilization's fragile veneer stripped away in a 'nether-world' of primitive violence.