Crustacean taxa

The subphylum Crustacea, of the phylum Arthropoda, has the greatest variety of forms found in any subphylum (or phylum) of animals. World wide, about 70,000 species have been named so far. There could easily be three to four times that many still unnamed.

Among crustaceans are the smallest and largest arthropods, from ‘tantilocarids’ less than a tenth of a millimetre long, to Japanese giant spider crabs with legs that can span over 3 metres.

The crustacean exoskeleton with its segments, many limbs and sculpted surfaces provides many features to identify them by. DNA analysis also provides greater accuracy than ever, to help sort out crustacean identities, relationships and evolution. 

There are at least 31 Orders of Crustacea. The Order Decapoda contains the most familiar ones (crabs, lobsters, shrimps and prawns). Sand hoppers belong in the Order Amphipoda; wood lice are in the Isopoda. Most other orders are less familiar but can be equally common.