Ecdysozoa

From Palaeos.org

Choanomonada
`--Metazoa
   `==Porifera (paraphyletic?)
      `==Radiata (paraphyletic?)
         `--Bilateria
            `==Acoelomorpha (paraphyletic?)
               |--Protostomia
               |  |--Ecdysozoa
               |  `--Lophotrochozoa
               `--Deuterostomia

(Arthropoda, Diplopoda, Polydesmida, Eurydesmidae)

The Ecdysozoa, for our purposes, are trated as bugs > slugs -- a stem group leading to the Arthropoda. However, they are better known as the "molting clade" -- the animal phyla with a cuticle which is molted (ecdysis). There is still considerable suspicion that they might not be a clade. However, the validity of the Ecdysozoa is coming increasingly to be accepted among workers in this field.

Phyla included are the Arthropoda, Tardigrada, Onychophora, and probably also the more primitive worm-like and "pseudocoelomate" groups like the Nematoda, Nematomorpha, Priapula, Kinorhyncha and Loricifera.

The largest of these phyla, and the most speciose phylum in the animal kingdom, the Arthropoda, includes insects, spiders, crabs, and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. Two smaller phyla, the Onychophora and Tardigrada, are close relatives of the arthropods and share these traits. These ogether make up the "Panarthropoda".

The Nematoda or roundworms, the second largest animal phylum. Roundworms are typically microscopic, and occur in nearly every environment where there is water. A number are important parasites. Smaller phyla related to them are the Nematomorpha or horsehair worms, which are invisible to the unaided eye, and the Kinorhyncha, Priapulida, and Loricifera. These groups have a reduced coelom, called a pseudocoelom.

Protostomia
`--Ecdysozoa
   |--Scalidophora
   |?--Protoconodonta†
   |   `--Chaetognatha
   |--+--Nematomorpha
   |  `--Nematoda
   `--o--Lobopoda 
      `--+--Tardigrada
         `--+--Anomalocarida
            `--Arthropoda

Phylogeny

<==Ecdysozoa [Introverta, Nematozoa]
   |--Cycloneuralia DH08
   |    |--+--+--Ancalagon DD04
   |    |  |  `--Fieldia DD04
   |    |  `--+--Scalidophora DH08
   |    |     `--Markuelia Val’kov 1983 DD04
   |    |          |--*M. secunda DD04
   |    |          `--M. hunanensis Dong, Donoghue et al. 2004 DD04
   |    `--Nematoida [Nematoidea] GE05
   |         |--Nematoda DH08
   |         `--Nematomorpha DH08
   `--Panarthropoda (see below for synonymy) MG06
        |  i. s.: Pambdelurion whittingtoni KBR09
        |--Tardigrada DH08
        `--+--Onychophora DH08
           `--+--Kerygmachela Budd 1993 KBR09, W96
              |    `--K. kierkegaardi B95
              `--Cephalata W96
                   |--Facivermis W96
                   `--+--Nectocaris Conway Morris 1976 W96
                      |    `--N. pteryx Conway Morris 1976 D95
                      `--+--Sprigginidae W96
                         |    |--Spriggina floundersi W96, CM98
                         |    `--Marywadea W96
                         `--+--Vendiamorpha W96
                            |    |  i. s.: Pseudovendia W96
                            |    |         Onega W96
                            |    |         Vendomia W96
                            |    |--Mialsemia W96
                            |    `--+--Parvancorina W96
                            |       `--+--Praecambridium W96
                            |          `--Vendia W96
                            `--Anomalopoda [Dinocarida] W96
                                 |--Bomakellia W96
                                 `--Anomalocaridea B95
                                      |--Cassubia Lendzion 1977 [Cassubiata] B95
                                      |    `--C. infracambriensis B95
                                      `--Anomalocarida [Anomalocaridata] B95
                                           |  i. s.: Hurdia Walcott 1912 B95
                                           |--+--Anomalocaris Whiteaves 1892 KBR09, B95
                                           |  |    `--*A. canadensis Whiteaves 1892 WB85
                                           |  `--+--Parapeytoia yunnanensis B02, KBR09
                                           |     `--Arthropoda KBR09
                                           `--+--+--Peytoia Walcott 1911 W96, WB85
                                              |  |    `--*P. nathorsti Walcott 1911 [=Anomalocaris nathorsti] WB85
                                              |  `--Laggania Walcott 1911 WB85
                                              |       `--*L. cambria Walcott 1911 WB85, KBR09, WB85
                                              `--+--Opabinia Walcott 1912 KBR09, B95
                                                 |    `--O. regalis B95
                                                 `--Tullimonstrum Richardson 1966 (see below for synonymy) B95
                                                      `--T. gregarium B95

Panarthropoda [Dicephalosomata, Haemopoda, Lobopoda, Mandibulopoda, Opabiniida, Opabiniidacea, Podophora, Probosciferidea, Tritocerebra, Uniantennata, Uniramia] MG06

Tullimonstrum Richardson 1966 [Tullimonstrida, Tullimonstridea] B95

* Type species of generic name indicated

References

[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.

[B02] Budd, G. E. 2002. A palaeontological solution to the arthropod head problem. Nature 417: 271-275.

[CM98] Conway Morris, S. 1998. The Crucible of Creation. Oxford University Press: Oxford.

[DD04] Dong, X-P., P. C. J. Donoghue, H. Cheng & J.-B. Liu. 2004. Fossil embryos from the Middle and Late Cambrian period of Hunan, south China. Nature 427: 237-240.

[DH08] Dunn, C. W., A. Hejnol, D. Q. Matus, K. Pang, W. E. Browne, S. A. Smith, E. Seaver, G. W. Rouse, M. Obst, G. D. Edgecombe, M. V. Sørensen, S. H. D. Haddock, A. Schmidt-Rhaesa, A. Okusu, R. M. Kristensen, W. C. Wheeler, M. Q. Martindale & G. Giribet. 2008. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature 452: 745-749.

[D95] Dzik, J. 1995. Yunnanozoon and the ancestry of chordates. Acta Palaeontologica Polonica 40: 341-360.

[GE05] Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.

[KBR09] Kühl, G., D. E. G. Briggs & J. Rust. 2009. A great-appendage arthropod with a radial mouth from the Lower Devonian Hunsrück Slate, Germany. Science 323: 771-773.

[MG06] Mallatt, J., & G. Giribet. 2006. Further use of nearly complete 28S and 18S rRNA genes to classify Ecdysozoa: 37 more arthropods and a kinorhynch. Molecular Phylogenetics and Evolution 40: 772-794.

[W96] Waggoner, B. M. 1996. Phylogenetic hypotheses of the relationships of arthropods to Precambrian and Cambrian problematic fossil taxa. Systematic Biology 45 (2): 190-222.

[WB85] Whittington, H. B., & D. E. G. Briggs. 1985. The largest Cambrian animal, Anomalocaris, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London 309: 569-609.

Credits

Palaeos com MAK020407 ATW050806; Wikipedia, this page MAK061012, phylogeny Christopher 13:11, 22 July 2010 (UTC)