Leptostraca

Leptostraca is an order of small marine malacostracan crustaceans with a bivalved carapace and a tail fan. Its members retain several anatomical features considered primitive among living malacostracans.

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Malacostraca: Malacostraca is the largest class of crustaceans, including crabs, shrimps, lobsters, and their relatives. Leptostraca is one of the orders within this crustacean class.
Leptostracan feeding: Leptostracan feeding uses thoracic limbs and mouthparts to collect and transfer food particles. Its limb-based feeding shows how the animal handles food beneath its bivalved carapace.
Nebalia: Nebalia is a genus of small marine leptostracans, commonly found on or within seafloor sediments. It is a familiar example of the order's small, shrimp-like living forms.
Waptia: Waptia is a Cambrian arthropod known from fossils in the Burgess Shale. Its bivalved carapace and appendages have prompted comparisons with early phyllocarids.
Stomatopoda: Stomatopoda is an order of marine malacostracans that includes mantis shrimps. Unlike leptostracans, stomatopods have a highly specialized raptorial second pair of thoracic limbs.
Crustacean carapace: A carapace is a cuticular shield covering part or all of a crustacean's body. In Leptostraca, the carapace forms two hinged valves around much of the body.
Leptostracan swimming: Leptostracan swimming is driven mainly by rhythmic movements of the abdominal pleopods. Pleopod strokes propel the animal while the tail fan helps with steering and escape.
Rhabdouraea: Rhabdouraea is a genus of living leptostracans recorded from marine habitats. Its distinct genus-level identity illustrates that living leptostracans extend beyond Nebalia.
Canadaspis: Canadaspis is an extinct Cambrian arthropod with a bivalved carapace. Its fossil anatomy provides a comparison for interpreting the deeper history of bivalved crustaceans.
Decapoda: Decapoda is an order of malacostracans that includes crabs, lobsters, and many shrimps. Decapods lack the leptostracan combination of a large bivalved carapace and leaflike thoracic limbs.