Which crustaceans have a carapace?

The carapace is a widespread feature among crustaceans, originating as a fold from the back of the head that may cover the dorsal surface or enclose the trunk and limbs.1

Crustaceans that possess a carapace include:

• Decapods: Many species feature a carapace that often projects forward into a pointed, toothed rostrum.1
• Notostracans (tadpole shrimps): These possess a large, domed carapace that covers part of the trunk.12
• Clam shrimps (orders Spinicaudata and Laevicaudata): Their carapace is split into two "valves," giving them a clamlike appearance.12
• Ostracods: These also feature a bivalved carapace.1
• Barnacles: They use a highly modified carapace to form a mantle that secretes their characteristic shell plates.1
• Cladocerans (water fleas): Most possess a bivalved carapace, though in some groups (such as Onychopoda and Haplopoda), it is reduced to a dorsal brood pouch.2
• Kazacharthra: An extinct order that featured a large carapace covering part of the trunk.2

Conversely, the carapace is absent in anostracans, amphipods, isopods, and members of the superorder Syncarida.12