The mournful cone was a masterpiece of benthic geometry, a spiraling weight of calcium carbonate that wore the colors of a bruised twilight. Its shell, marked in obsidian and ochre was meant also to warn predators - the mollusk possessed a unique toxin, a complex chemical cocktail refined over a millennia that could paralyze its prey in an instant. This molecular architecture is now a broken blueprint. While its extant cousins of the same genus continue to carry the secret, parts of it are permanently missing.
I imagine the last one retreating into the shadow of a darkening reef, its siphon tasting the water for a kin that would never signal back.