Chelicerata is a subphylum of arthropods that includes animals such as spiders, scorpions, and horseshoe crabs. They are characterized by having chelicerae, which are specialized mouthparts used for feeding. Unlike insects, chelicerates do not have antennae and typically have eight legs. Chelicerates are divided into several classes, including Arachnida, which encompasses spiders and scorpions, and Merostomata, which includes horseshoe crabs. Most chelicerates are terrestrial, but some, like horseshoe crabs, are aquatic. They play important roles in ecosystems as predators and scavengers.