Species similar to or like Sea spider

Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. Wikipedia

Horseshoe crabs are marine and brackish water arthropods of the family Limulidae, suborder Xiphosurida, and order Xiphosura. Misnomer, as they are not true crabs, nor even crustaceans, as crabs are, but a different order of arthropod. Wikipedia

Marine arthropod in the family Pycnogonidae. Found on the western seaboard of North America. Wikipedia

An arthropod (, (gen. Invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages. Wikipedia

Arthropod group which also includes millipedes and other multi-legged creatures. Centipedes are elongated metameric creatures with one pair of legs per body segment. Wikipedia

Order of arthropods related to arachnids. They are sometimes called horseshoe crabs (a name applied more specifically to the only extant family, Limulidae). Wikipedia