Malacostraca
class of crustaceans
Malacostraca is the second largest of the six classes of pancrustaceans after insects, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobsters, spiny lobsters, crayfish, shrimp, krill, prawns, isopods, amphipods, mantis shrimp, and many other less familiar animals. They are abundant in all marine environments and have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments (rarely 21), and divided into a head, thorax, and abdomen.
Etymology
The name Malacostraca is from Ancient Greek μαλακός (malakós) 'soft' and ὄστρακον (óstrakon) 'shell'. The word was used by Aristotle, who contrasted them with oysters, in comparison with which their shells are pliable.
It was applied to this taxon by French zoologist Pierre André Latreille in 1802. He was curator of the arthropod collection at the National Museum of Natural History in Paris.
This scientific name is a misnomer, since the shell is soft only immediately after moulting, and is usually hard.
Malacostracans are sometimes contrasted with entomostracans, a name applied to all crustaceans outside the Malacostraca, and named after the obsolete taxon Entomostraca.
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This entry incorporates text from “Malacostraca” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.