Sea spiders are marine arthropods of the order Pantopoda (lit. ‘all feet’), belonging to the class Pycnogonida, hence they are also called pycnogonids (named after Pycnogonum, the type genus; with the suffix -id). They are cosmopolitan, found in oceans around the world. There are over 1,300 known species, with legs ranging from 1 mm (0. 04 in) to over 70 cm (2. 3 ft). Most are toward the smaller end of this range in relatively shallow depths; however, they can grow to be quite large in Antarctic and deep waters.

Pantopoda. Retrieved May, 08 2021, from en.wikipedia.org/wiki/Sea_spider.

The subphylum Chelicerata (New Latin, from French chélicère, from Greek χηλή, khēlē "claw, chela" and κέρας, kéras "horn") constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, arachnids (including scorpions, spiders, and potentially horseshoe crabs), and several extinct lineages, such as the eurypterids and chasmataspidids.

Chelicerata. Retrieved May, 08 2021, from en.wikipedia.org/wiki/Chelicerata.