Chelicerata - Spiders, Horseshoe Crabs, Sea Spiders, Scorpions, Mites

This subphylum includes a diverse group of species including ticks, spiders, and horseshoe crabs. Chelicerates have bodies divided into two segments, the prosoma and the opisthosoma.

The promosa is the front part of the body and it has six pairs of appendages including four pairs of walking legs, a pair of jointed jaws called chelicerae, and a pair of antenna-like pedipalps. In some species, like the scorpions, the pedipalps are claws!The opisthosoma is the rear segment and it lacks appendages.

Most species are found on land, but some, like the horseshoe crab, are found in the ocean. Some species, like ticks and mites, are parasites. Chelicerates, unlike most arthropods, don't have antennae.

Classes
Arachnida (spiders, scorpians, ticks, mites)   Merostomata (horseshoe crabs)	Pycnogonida (sea spiders)