Bilateria

Nemertoderma westbladi, from here.

Belongs within: Epitheliozoa.
Contains: Orthonectida, Rhombozoa, Acoela, Ecdysozoa, Chaetognatha, Lophotrochozoa, Deuterostomia.

The Bilateria is a major clade of animals characterised by the possession of a bilaterally symmetrical body plan, together with a mesodermal germ layer giving rise to circular and longitudinal muscles (Cannon et al. 2016). Recent phylogenetic analyses of the Bilateria have mostly agreed that the Xenacoelomorpha, marine worms lacking a through-gut or protonephridia, represent the sister taxon of the majority of Bilateria in the Nephrozoa. The Mesozoa, a group of simple endoparasitic bilaterians lacking a developed mesoderm, are of uncertain relationships within the Bilateria and are almost certainly polyphyletic.

Bilateria [Acoelomata, Coelomata, Enterocoela, Heteraxonia, Intestina, Metahelminthes, Triploblastica]
    |--Mesozoa [Moruloidea] ZHT01
    |    |--Orthonectida S72
    |    `--Rhombozoa S72
    |--Xenacoelomorpha CV16
    |    |--Xenoturbella Westblad 1949 HO09, BN03 [Xenoturbellida]
    |    |    `--*X. bocki Westblad 1949 BN03
    |    `--Acoelomorpha [Archoophora] HO09
    |         |  i. s.: Avagina BK77
    |         |           |--A. glandulifera BK77
    |         |           |--A. incola [=Haplodiscus incola] BK77
    |         |           `--A. vivipara BK77
    |         |         Faerlea echinocardii BK77
    |         |         Otocoelis chirodotae BK77
    |         |--Acoela HO09
    |         `--Nemertodermatida HO09
    |              |  i. s.: Nemertinoides elongatus GD00
    |              |--Ascoparia [Ascopariidae] CV16
    |              `--+--Nemertoderma [Nemertodermatidae] CV16
    |                 |    |--N. bathycola Steinböck 1930 GD00
    |                 |    `--N. westbladi HO09
    |                 `--+--Sterreria psammicola (Sterrer 1970) CV16, H01
    |                    `--Meara stichopi CV16
    `--Nephrozoa [Eubilateria, Eutriploblastica] HO09
         |  i. s.: Amimomus de Montfort 1808 (n. d.) T64
         |           `--*A. elephantinus de Montfort 1808 (n. d.) T64
         |         Serripecten M49
         |           |--S. beethami M49
         |           `--S. hutchinsoni M49
         |         Vernanimalcula Chen, Bottjer et al. 2004 CB04
         |           `--*V. guizhoena Chen, Bottjer et al. 2004 CB04
         |--Protostomia (see below for synonymy) HO09
         |    |--Ecdysozoa HO09
         |    `--+--Chaetognatha HO09
         |       `--Lophotrochozoa HO09
         `--Deuterostomia HO09

Bilateria incertae sedis:
  Titerina rokycanensis Kraft & Mergl 1989 S02
  Enchostoma Miller & Gurley 1896 F62
    `--‘Hyolithes’ milleri Sinclair 1946 (see below for synonymy) F62
  Haileyia Ruedemann 1934 H62
    `--*H. adhaerens Ruedemann 1934 H62
  Hesionites Fritsch 1907 H62
    `--*H. bioculata Fritsch 1907 H62
  Hirudopsis Moberg & Segerberg 1906 H62
    `--*H. koepingensis Moberg & Segerberg 1906 H62
  Klakesia Ruedemann 1934 H62
    `--*K. simplex Ruedemann 1934 H62
  Propolynoe Fritsch 1907 H62
    `--*P. laccoei Fritsch 1907 H62
  Protoscolex Ulrich 1878 H62
    `--*P. covingtonensis Ulrich 1878 H62
  Redoubtia Walcott 1918 H62
    `--*R. polypodia Walcott 1918 H62
  Sarcionata Costa 1856 H62
    `--*S. proboscidata Costa 1856 H62
  Tosalorbis Katto 1960 H62
    `--*T. hanzawai Katto 1960 H62
  Balanophorus Briganti 1825 L09
  Anticalyptraea Quinstedt 1867 [incl. Autodetus Lindström 1884] KC60
  Furia Linnaeus 1758 L58
    `--*F. infernalis Linnaeus 1758 L58

‘Hyolithes’ milleri Sinclair 1946 [=Hyolithes lanceolatus Miller 1892 non Theca lanceolatus Morris 1845, *Enchostoma lanceolatum] F62

Protostomia [Aschelminthes, Gastroneuralia, Gephyrea, Nemathelminthes, Pleuropteria, Proterostoma, Pseudocoelomata, Schizocoela] HO09

*Type species of generic name indicated

REFERENCES

[BK77] Barel, C. D. N., & P. G. N. Kramers. 1977. A survey of the echinoderm associates of the north-east Atlantic area. Zoologische Verhandelingen 156: 1–159.

[BN03] Bourlat, S. J., C. Nielsen, A. E. Lockyer, D. T. J. Littlewood & M. J. Telford. 2003. Xenoturbella is a deuterostome that eats molluscs. Nature 424: 925–928.

[CV16] Cannon, J. T., B. C. Vellutini, J. Smith, III, F. Ronquist, U. Jondelius & A. Hejnol. 2016. Xenacoelomorpha is the sister group to Nephrozoa. Nature 530: 89–93.

[CB04] Chen, J.-Y., D. J. Bottjer, P. Oliveri, S. Q. Dornbos, F. Gao, S. Ruffins, H. Chi, C.-W. Li & E. H. Davidson. 2004. Small bilaterian fossils from 40 to 55 million years before the Cambrian. Science 305: 218–222.

[F62] Fisher, D. W. 1962. Small conoidal shells of uncertain affinities. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W98–W143. Geological Society of America, and University of Kansas Press.

[GD00] Giribet, G., D. L. Distel, M. Polz, W. Sterrer & W. C. Wheeler. 2000. Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: a combined approach of 18S rDNA sequences and morphology. Systematic Biology 49: 539–562.

[HO09] Hejnol, A., M. Obst, A. Stamatakis, M. Ott, G. W. Rouse, G. D. Edgecombe, P. Martinez, J. Baguña, X. Bailly, U. Jondelius, M. Wiens, W. E. G. Müller, E. Seaver, W. C. Wheeler, M. Q. Martindale, G. Giribet & C. W. Dunn. 2009. Assessing the root of bilaterian animals with scalable phylogenomic methods. Proceedings of the Royal Society of London Series B—Biological Sciences 276 (1677): 4261–4270.

[H01] Hooge, M. D. 2001. Evolution of body-wall musculature in the Platyhelminthes (Acoelomorpha, Catenulida, Rhabditophora). Journal of Morphology 249: 171–194.

[H62] Howell, B. F. 1962. Worms. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W144–W177. Geological Society of America, and University of Kansas Press.

[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

[L09] Lea, A. M. 1909. Revision of the Australian and Tasmanian Malacodermidae. Trans. Ent. Soc. Lond. 1909 (1): 45–251, pls 2–6.

[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii: Holmiae.

[M49] Mason, B. 1949. The geology of Mandamus-Pahau district, north Canterbury. Transactions and Proceedings of the Royal Society of New Zealand 77 (3): 403–428.

[S72] Stunkard, H. W. 1972. Clarification of taxonomy in the Mesozoa. Systematic Zoology 21 (2): 210–214.

[S02] Szaniawski, H. 2002. New evidence for the protoconodont origin of chaetognaths. Acta Paleontologica Polonica 47 (3): 405–419.

[T64] Teichert, C. 1964. Doubtful taxa. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda—General Features—Endoceratoidea—Actinoceratoidea—Nautiloidea—Bactritoidea pp. K484–K490. The Geological Society of America and the University of Kansas Press.

[ZHT01] Zrzavý, J., V. Hypša & D. F. Tietz. 2001. Myzostomida are not annelids: molecular and morphological support for a clade of animals with anterior sperm flagella. Cladistics 17: 170–198.

Last updated: 17 April 2017.