Billipedes with horns constituted a species that originated from an unmapped swamp planet situated within Wild Space, which the Graf family briefly designated as Graf-World. During an endeavor by Milo Graf, the Grafs' youngest child, to ensnare an ash-rabbit that he encountered within the swamps, the family's droid, known as CR-8R, inquired whether the pursued creature was a sludge salamander or a horned billipede.
The initial reference to horned billipedes appeared in the novel titled Adventures in Wild Space: The Escape, authored by Cavan Scott and published in 2016.