Subclass EUMALACOSTRACA Grobben, 1892

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Introduction

The Malacostraca are the largest and most diverse of the six classes of the Subphylum Crustacea. The others are Remipedia (remipedes), Cephalocarida (cephalocarids), Branchiopoda (fairy shrimps, clam shrimps, shield shrimps and water fleas), Ostracoda (ostracods) and Maxillipoda (copepods, barnacles, fish lice, tongue worms, and free-living and parasitic barnacles). This is the classification adopted by Martin & Davis (2001) in their list of all crustacean families. Other authors, such as Bowman & Abele (1982) who compiled an earlier list of families, combined some of these classes.

The subclass Eumalacostraca, with two others, the Phyllocarida (leptostracans or nebaliaceans) and the Hoplocarida (stomatopods), comprise the Malacostraca. The subclass Eumalacostraca is by far the largest of the malacostracan subclasses. It includes about 40,000 species worldwide, mostly from marine environments, but also includes some from freshwater or terrestrial habitats. Crabs, shrimps, lobsters, prawns and crayfish are among the most familiar.

The Eumalacostraca are recognised by the possession of five cephalic (head) segments, eight thoracomeres (thoracic segments) and six pleomeres (abdominal segments). Antenna 1 is biramous. The endopodites (inner branches) of the thoracopods (thoracic limbs) are always jointed and usually function as walking or swimming legs, but as many as three anterior pairs may contribute to the feeding limbs of the head anteriorly (as maxillipeds). Pleopods (abdominal limbs) are usually present. The sixth pair and sometimes others are differentiated into uropods. The uropods may form a tailfan, with the telson, appended to the end of the pleon. The gonopores are on the eighth thoracomere in the male and sixth in the female. Further anatomical details of the subclass have been given by Kaestner (1980) and Schram (1986).

The subclass Eumalacostraca comprises three superorders, Syncarida, Peracarida and Eucarida. The peracaridan orders are included in this database, which was derived by combining the databases on which the Zoological Catalogue of Australia, Volumes 19.2A and 19.2B (Poore 2002; Lowry & Stoddart 2003) were based. Diagnoses are provided for all taxa of family rank or higher, and for some subfamilies.{42892}{42979}{48520}{42789}

Diagnosis

Malacostracans of highly variable morphology, but with 'caridoid facies' body plan of five-segmented cephalon, eight-segmented thorax, and six-segmented abdomen, plus telson; zero to three thoracic somites fused with head, their respective appendages usually modified as maxillipeds; antennules and antennae primitively biramous; antennae often with scale-like exopod; most with well developed carapace, but secondarily reduced in syncarids and some peracarids; gills primitively as thoracic epipods; tail fan composed of telson plus paired uropods (typically lost in Brachyura); abdomen typically long and muscular, but greatly reduced, shortened, and little visible dorsally in Brachyura.
(Modified after Brusca & Brusca 1990).

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