Protozoea hilgendorfi, copyright Ghedoghedo.

Belongs within: Malacostraca.
Contains: Hoplocarida, Decapoda, Syncarida, Euphausiacea, Thermosbaenacea, Mysidacea, Isopoda, Cosinzeneacea, Cumacea, Tanaidacea, Amphipoda.

The Eumalacostraca are a clade containing most of the familiar macroscopic crustaceans, such as amphipods, isopods and shrimps, characterised by rod-shaped appendages on thoracic segments 1–8 and association of the uropods and telson to form a tail fan (Ax 1999). Authors have differed on whether the Hoplocarida should be included in the Eumalacostraca. Eumalacostraca sensu stricto (or Caridoida), excluding Hoplocarida, are united by fusion of the rostrum to the remainder of the head and modification of the pleon and tail fan as an escape device (Ax 1999).

Within the Caridoida, certain authors have supported a clade Eucarida, including the Decapoda, Euphausiacea and Amphionides, characterised by the fusion of the carapace to the thoracic segments to form a cephalothorax. However, others have placed the Euphausiacea closer to the Syncarida and Peracarida in a clade Xenommacarida. Xenommacarida may be united by ommatidia with a two-part crystalline cone, contrasting with the four-part crystalline cone found in Hoplocarida and Decapoda (Ax 1999). The Peracarida include amphipods, isopods and related taxa; most peracarids possess a ventral brood pouch formed from thin flattened plates (oostegites) arising from the base of the legs.

Possible stem-eumalacostracans include the Thylacocephala, a group of crustaceans of uncertain affinities known from the Silurian to the Cretaceous in which the entire body was typically covered by a large carapace, obscuring the body segmentation (Lange & Schram 2002).

<==Eumalacostraca [Branchiogastra, Eucarida, Squillares]
    |    |  i. s.: Thylacocephalus cymolopos Lange et al. 2001LS02
    |    |         Dollocaris ingens van Straelen 1923LSE13, LS02
    |    |         Austriocaris Glaessner 1931FGS04
    |    |         Ostenocaris Arduini et al. 1982LS02
    |    |           `--O. cypriformis (Arduini, Pinna & Teruzzi 1980)LS02
    |    |         Kilianicaris lerichei Van Straelen 1923BWW93
    |    |--ConchyliocaridaBWW93
    |    |    |--Silesicaris nasuta Gürich 1926BWW93
    |    |    `--Clausocaris lithographica (Oppenheim 1888)BWW93
    |    `--ConcavicaridaBWW93
    |         |--Concavicaris Rolfe 1961FGS04
    |         |--Pseuderichthus cretaceus Dames 1886BWW93
    |         `--ProtozoeaBWW93
    |              |--P. damesi Roger 1946LS02
    |              `--P. hilgendorfi Dames 1886LS02
            |  `--Amphionides [Amphionidacea, Amphionididae]LSE13
            |       `--A. reynaudiiA99
                    `--Peracarida (see below for synonymy)MD01
Eumalacostraca incertae sedis:
  Phasmatocarcinus discophtalmusG20
    |--E. hyalinusG20
    `--E. vulgarisG20
  WaterstonellaBWW93 [Waterstonellidae, WaterstonellideaB95]
    `--W. grantonensis Schram 1979BWW93
  Eocaridacea [Eocarida]B95
    |  i. s.: Peachella strongiS74
    |--Essoidia [Essoidiidae]S74
    |    `--E. epiceron Schram 1974S74
    |--Anthracophausia [Anthracophausiidae]BWW93
    |    |--A. dunsiana Peach 1908BWW93
    |    `--A. ingelsorum Brooks 1962BWW93
    |--Belotelson [Belotelsonidae, Belotelsonidea]G88
    |    |--B. magister Packard 1886S74
    |    `--B. traquairi (Peach 1882)BWW93
         |--Eocaris oervigi Brooks 1962G88, S77
              |--D. cuylerensis (Wells 1957)S77
              `--D. destinezi (Van Straelen 1943)S77

Peracarida [Arthrostraca, Brachycarida, Edriophthalma, Gammarinae, Hemicaridea, Mancoidea, Neocarida]MD01

*Type species of generic name indicated


[A99] Ax, P. 1999. Das System der Metazoa II. Ein Lehrbuch der phylogenetischen Systematik. Gustav Fisher Verlag: Stuttgart (translated: 2000. Multicellular Animals: The phylogenetic system of the Metazoa vol. 2. Springer).

[B95] Bousfield, E. L. 1995. A contribution to the natural classification of Lower and Middle Cambrian arthropods: food-gathering and feeding mechanisms. Amphipacifica 2: 3–34.

[BWW93] Briggs, D. E. G., M. J. Weedon & M. A. Whyte. 1993. Arthropoda (Crustacea excluding Ostracoda). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 321–342. Chapman & Hall: London.

[FGS04] Feldmann, R. M., A. A. Garassino & C. E. Schweitzer. 2004. The presumed decapod, Palaeopemphix Gemmellaro, 1890, is a unique member of the Phyllocarida (Palaeopemphicida: Palaeopemphidae). Journal of Palaeontology 78: 340–348.

[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.

[G88] Gray, J. 1988. Evolution of the freshwater ecosystem: the fossil record. Palaeogeography, Palaeoclimatology, Palaeoecology 62: 1–214.

[LS02] Lange, S., & F. R. Schram. 2002. Possible lattice organs in Cretaceous Thylacocephala. Contributions to Zoology 71 (4): 159–169.

[LSE13] Legg, D. A., M. D. Sutton & G. D. Edgecombe. 2013. Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature Communications 4: 2485.

[MD01] Martin, J. W., & G. E. Davis. 2001. An updated classification of the Recent Crustacea. Natural History Museum Los Angeles County, Science Series 39: 1–124.

[S74] Schram, F. R. 1974. Convergences between Late Paleozoic and modern caridoid Malacostraca. Systematic Zoology 23 (3): 323–332.

[S77] Schram, F. R. 1977. Paleozoogeography of Late Paleozoic and Triassic Malacostraca. Systematic Zoology 26 (4): 367–379.

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