Sea spiders, also called
Pantopoda or
pycnogonids, ('pycno-' closely packed, 'gonid'
gonidia) are marine
arthropods of
class Pycnogonida. They are
cosmopolitan, found especially in the
Mediterranean and
Caribbean Seas, as well as the
Arctic and
Antarctic Oceans. There are over 1300 known species, ranging in size from to over in some deep water species. Most are toward the smaller end of this range in relatively shallow depths, however, they can grow to be quite large in Antarctic waters.