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Eumalacostraca

(Subclass)

Overview

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The Eumalacostraca (Greek: "true soft shell") are a subclass of , containing almost all living malacostracans, about 22,000 described species. (The outgroups are the Phyllocarida and possibly the Hoplocarida or mantis shrimps.)

Eumalacostracans have 19 segments (5 cephalic, 8 thoracic, 6 abdominal). The thoracic limbs are jointed and used for swimming or walking. The common ancestor is thought to have had a carapace, and most living species possess one, but it has been lost in some subgroups.

Classification

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Martin and Davis [1] present the following classification of living eumalacostracans into orders, to which extinct orders have been added, indicated by †.

The group as originally described by Karl Grobben [2] included the Stomatopoda (mantis shrimp), and some modern experts continue to use this definition. Here we follow Martin and Davis in excluding them; they are placed in their own subclass, Hoplocarida.

Subclass ''''Eumalacostraca'''' Grobben, 1892

Photos

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Taxonomy

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The Subclass Eumalacostraca is a member of the Class Crustacea. Here is the complete "parentage" of Eumalacostraca:

The Subclass Eumalacostraca is further organized into finer groupings including:

Orders

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Amphionidacea

Amphionides reynaudii is the sole representative of the Amphionidacea, and is a small (less than one inch long) planktonic crustacean found throughout the world's tropical oceans, mostly in shallow waters. Morphologically, Amphionides is somewhat unusual, with many body parts being reduced or absent. For example, it has only one pair of mouthparts — the maxillae — the mandibles and maxillules being absent. [more]

Amphipoda

Amphipoda (amphipods) are an of animals that includes over 7,000 described species of shrimp-like crustaceans ranging from 1 mm to 140 mm in length. [more]

Anaspidacea

Anaspidacea is an of crustaceans, comprising eleven genera in four families. Species in the family Anaspididae vary from being strict stygobionts (only living underground) to species living in lakes, streams and moorland pools, and are found only in Tasmania. Koonungidae is found in Tasmania and the south-eastern part of the Australian mainland, where they live in the burrows made by crayfish and in caves. The families Psammaspididae and Stygocarididae are both restricted to caves, but Stygocarididae has a much wider distribution than the other families, with Parastygocaris having species in New Zealand and South America as well as Australia; two other genera in the family are endemic to South America, and one, Stygocarella, is endemic to New Zealand . [more]

Bathynellacea

[more]

Cumacea

Cumacea is an of small marine crustaceans, occasionally called hooded shrimps. Their unique appearance and uniform body plan makes them easy to distinguish from other crustaceans. [more]

Decapoda

The decapods or Decapoda (literally means "ten footed") are an order of within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. [more]

Euphausiacea

Krill are a type of -like marine invertebrate animal. These small crustaceans are important organisms of the zooplankton, particularly as food for baleen whales, manta rays, whale sharks, crabeater seals, and other seals, and a few seabird species that feed almost exclusively on them. Another name is euphausiids, after their taxonomic order Euphausiacea. The name krill comes from the Norwegian word krill meaning "young fry of fish," which is also often attributed to other species of fish. [more]

Isopoda

Isopods are one of the most diverse orders of , with many species living in all environments, but are most common in shallow marine waters. Unlike most crustaceans, isopods are successful on land (suborder Oniscidea, woodlice, which also includes sea slaters), although their greatest diversity remains in the deep sea (suborder Asellota). There are also several parasitic species within the genus Cymothoa, commonly known as "tongue-biters" for their habit of nibbling off fishes' tongues and attaching themselves to the floor of the host's mouth. The isopods are an ancient group with fossils known from the Carboniferous (suborder Phreatoicidea, family Paleophreatoicidae) that only differ slightly from modern southern hemisphere freshwater phreatoicideans. There are 4000 known species. [more]

Lophogastrida

The Mysidacea is a group of small, -like creatures comprising the two related orders Mysida and Lophogastrida. They are sometimes referred to as opossum shrimps though that name is also used for individual species (e.g. Neomysis americana). [more]

Mysida

The Mysidacea is a group of small, -like creatures comprising the two related orders Mysida and Lophogastrida. They are sometimes referred to as opossum shrimps though that name is also used for individual species (e.g. Neomysis americana). [more]

Spelaeogriphacea

[more]

Tanaidacea

[more]

Thermosbaenacea

Thermosbaenacea is a group of that live in thermal springs in fresh water, brackish water and anchialine habitats. They have occasionally been treated as a distinct superorder (Pancarida), but are generally considered to belong to the Peracarida . Due to their troglobitic lifestyle, thermosbaenaceans lack visual pigments and are therefore blind. [more]

At least 16 species and subspecies belong to the Order Thermosbaenacea.

More info about the Order Thermosbaenacea may be found here.

References

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  1. ^ J. W. Martin & G. E. Davis (2001). An Updated Classification of the Recent Crustacea. Natural History Museum of Los Angeles County. 
  2. ^ C. Grobben (1892). "Zur Kenntnis des Stammbaumes und des Systems der Crustaceen". Sitzber. K. Akad. Wiss., Vienna, Math. Nat. Cl. 101: 237–274. 

Sources

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Last Revised: November 18, 2008