Phylogeny of Malacostraca

[5] To resolve a well-supported eumalacostracan phylogeny and obtain a robust tree, it will be necessary to look beyond the most commonly utilized sources of data (nuclear ribosomal and mitochondrial sequences).

The Phyllocarida is a group of about 36 small marine species that are distributed across planet and possess a characteristic large bivalve carapace and an elongated abdomen with no uropods.

In addition, there is an enigmatic eucarid species, Amphionides reynaudii, which is the sole representative of its order, but due to the loss of several features resulting from its small size, its classification has been unclear.

With the exception of thermosbaenacean species, a characteristic of the members of this group is that they brood their young in a marsupium formed by branches (endites) of their thoracopods, called oostegites.

Amphipoda is a highly diverse group of 8,000 species, ranging from the Caprellida with a long and narrow body shape (skeleton shrimp) to the shrimp-like Gammaridea (scuds and sand hoppers).

The remaining Peracarida orders are the cryptic and either moderately abundant, Cumacea and Tanaidacea, or are extremely rare and relictual, Mictacea, Spelaeogriphacea, and Thermosbaenacea.

There are about 1,600 members of the Cumacea, these are small burrowing crustaceans which have a characteristic large bulbous carapace (covering three thoracic segments) and an elongated abdomen which finishes in a pleotelson with stylus-like uropods, in fact due to their peculiar shape they are sometimes called hooded shrimp.

Tanaidacea is a group of 1,500 species which are small burrowing or tube-dwelling crustaceans with a short carapace (covering two thoracic segments) that possess a pair of chelate second thoracopods (gnathopods).

[9][17][18] The major feature that emerges from the picture of the phylogeny of the Malacostraca is that their diversity has resulted in several studies proposing dramatically different phylogenetic trees.

[20] Phyllocarida Hoplocarida Decapoda Amphionidacea Euphausiacea Thermosbaenacea Mysida Lophogastrida Spelaeogriphacea Mictacea Cumacea Tanaidacea Isopoda Anaspidacea Bathynellacea