This list of prehistoric malacostracans illustrates the genera from the fossil record that have ever been considered to be malacostracans, a class of crustacean arthropod, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful ( nomina dubia ), or were not formally published ( nomina nuda ), as well as junior synonyms of more established names, and genera that are no longer considered malacostracans. [1] The majority of the genera are from the order Decapoda, for which a recent synopsis allows invalid names to be excluded. [2]