Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The most famous Jurassic deposit in the world is found in the Solnhofen and Eichstätt regions of Germany. The limestone that makes up this formation was formed in a lagoon 155 million years ago. Conditions in this lagoon were ideal for creating fossils of anything that washed from the sea, the land, or fell from the sky. The calm and poorly oxygenated waters lacked the biological factors that normally destroy soft parts.