REPTANTIA

The 'Reptantia' is a group of decapod crustaceans, including lobsters, crabs and many other well-known creatures. In older classifications, Reptantia is a sub-order alongside Natantia, with Reptantia containing the walking forms, and Natantia the swimming forms (prawns, shrimp and boxer shrimp). This classification is no longer valid, however, and Reptantia is now a clade within the sub-order Pleocyemata.
The name Reptantia means "those that walk", and contains those decapods whose primary mode of locomotion is to walk along a surface using the pereiopods rather than swimming through the water with the pleopods. Despite this, many reptants are able to propel themselves through the water, and many natants can and will walk.
Although relationships within the Reptantia are still somewhat unclear, a number of groups can be identified (fossil groups are not considered here):

★ Polychelidae - blind, deep-sea animals with long pincers

★ Achelata - a group comprising spiny lobsters, slipper lobsters and furry lobsters, all of which lack claws

★ Glypheoidea - a group of lobster-like animals thought to be extinct until the discovery of ''Neoglyphea inopinata'' in 1975

★ Astacidea - true (clawed) lobsters, including reef lobsters, along with freshwater crayfish

★ Thalassinidea - a group of delicate, burrowing animals, variously known as "mud lobster" and "ghost shrimp"

★ Anomura - hermit crabs, king crabs, porcelain crabs, squat lobsters, hippoids and a couple of other unusual animals

★ Brachyura - true crabs
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'Reptantia' is also used for a group of nemertean worms.