Narrative

Crabs (Decapoda\Brachyura) are a group of the Shrimp and Crab Order (Order Decapoda). The crabs are a diverse group. However, one can usually recognize a crab because of its small abdomen, and a thorax that may be as wide as or wider than it is long.

Shrimps and Crabs (Order Decapoda) contains most of the larger freshwater and marine species of crabs, crayfish, shrimp, and lobsters. They have a total of ten pairs of legs, four pairs of which are used for walking. Frequently the first pair of legs has been modified into pinchers used for eating and defense.

Here the Decapoda have been separated into five different suborders that match the adult shapes of the various life forms. They are as follows:

Natantia - Shrimp-like
Brachyura - Crab-like
Anomura - Hermit Crabs and relatives
Astacidea - Crayfish and Lobster-like
Palinura - Spiney Lobsters and Spanish Lobster

The sub-classification of the Order Decapoda is in a state of change. For a short summary of this situation, please refer to pages two and three of Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States by Austin Williams published by the Smithsonian Press, Washington, D.C., in l984. If one uses adult shape for classification, one gets one organization, and if one uses larvae shape for classification, one gets a different organization.

Taxonomy

References