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1 Taxonomy

A number of more or less unrelated crustaceans also have the word "shrimp" in their common name. Examples are the mantis shrimp and the opposum or mysid shrimp, both of which belong to the same class ( Malacostraca) as the true shrimp, but constitute two different orders within it, the Stomatopoda and the Mysidacea.

Also, debates on the taxonomy of the decapods continues, and not all authorities recognise Natantia as a valid grouping, while some would place infraorders or superfamiliesIn biology, a superfamily is a taxonomic grade intermediate between suborder and family. Plant superfamilies end with the suffix acea animal superfamilies end with oidea (although in older books the suffix acea is still used). Superfamily can also refer t beneath it.

The most recent classifications tend to remove some of the shrimp, in particular the family Penaeidae , from Natantia. They then become classified within the suborder Dendrobranchiata and the infraorder Penaeoida (some authors treat Penaeoida as a suborder). The rest of the shrimp belong to a different suborder, the Pleocyemata ; Natantia may serve as the name for an infraorder within this, though the name Caridea occurs more frequenly. In this scheme, the members of the Pleocyemate infraorder Caridea are regarded as the "true shrimp", while the members of the Dendrobranchiate infraorder Penaeoida are referred to as "penaeid shrimp". The table at the right reflects the older classification.

The points that seem relatively fixed amidst this fluidity are:

• All animals in the families listed at right would normally be named as shrimp, but they may not constitute a monophyleticIn phylogenetics, a group is monophyletic (greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. Taxonomic groups that contain organisms but group.
• All current classifications place all true shrimps in the order Decapoda, which groups them with crabCrabs are various species of decapods. They are crustaceans with five pairs of legs, the first pair modified to form a pair of pincers, a flattish shell, and a short, broad abdomen folded under its thorax. There are two main groups of crabs: the Brachyuras, lobsterClawed lobsters comprise a family Nephropidae of large marine crustaceans. Smaller varieties are sometimes called "lobsterettes". Lobsters are invertebrates, and have a tough exoskeleton, which protects them. Like all arthropods, lobsters must molt in ords and krill.
• There are some animals whose common name includes the word "shrimp" that definitely belong to other groups of crustaceans.

The usage of the common name "shrimp" also varies: zoologically, all crustaceans belonging to Natantia (or to a corresponding list of families) are called shrimps, but in common usage, especially in relation to cooking, some of the large ones are known as prawns.