Edmond Hamilton's 'Monsters of Mars' – Astounding Stories Pulp Cover, 1931

Interplanetary warfare meets alien predation as energy beams slash across a jagged Martian landscape. Two human explorers in khaki uniforms flee in terror from a trio of massive bipedal reptilian monsters — crocodilian jaws agape, clawed hands reaching — beneath towering dark spires and crimson ray-beams lighting the alien sky. The scene captures the classic pulp threat of extraterrestrial fauna overwhelmingly hostile to human explorers on the Red Planet.