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For other uses, see Phyla.
Life Domain Kingdom Phylum Class Order Family Genus Species

In biology, a phylum (/ˈfləm/; plural: phyla)[note 1] is a taxonomic rank below kingdom and above class. Traditionally, in botany the term division was used instead of "phylum", although from 1993 the International Code of Nomenclature for algae, fungi, and plants accepted the designation "phylum".[1][2] The kingdom Animalia contains approximately 35 phyla, Plantae contains 12, and Fungi contains 7.[citation needed] Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.

General description and familiar examples[edit]

The definitions of zoological phyla have changed importantly[clarification needed] from their origins in the six Linnaean classes and the four "embranchements" of Georges Cuvier.[3] Haeckel introduced the term phylum, based on the Greek word phylon ('tribe' or 'stock').[4] In plant taxonomy, Eichler (1883) classified plants into five groups, named divisions.[5]


Definition based on genetic relation[edit]

The most important objective measure in the above definitions is the "certain degree"—how unrelated do organisms need to be to be members of different phyla? The minimal requirement is that all organisms in a phylum should be clearly more closely related to one another than to any other group.[7] Even this is problematic because the requirement depends on knowledge of organisms' relationships: as more data become available, particularly from molecular studies, we are better able to judge the relationships between groups. So phyla can be merged or split if it becomes apparent that they are related to one another or not. For example, the bearded worms were described as a new phylum (the Pogonophora) in the middle of the 20th century, but molecular work almost half a century later found them to be a group of annelids, so the phyla were merged (the bearded worms are now an annelid family).[8] On the other hand, the highly parasitic phylum Mesozoa was divided into two phyla, Orthonectida and Rhombozoa, when it was discovered the Orthonectida are probably deuterostomes and the Rhombozoa protostomes.[9]


Definition based on body plan[edit]



The approach is useful because it makes it easy to classify extinct organisms as "stem groups" to the phyla with which they bear the most resemblance, based only on the taxonomically important similarities.[7] However, proving that a fossil belongs to the crown group of a phylum is difficult, as it must display a character unique to a sub-set of the crown group.[clarification needed][7] Furthermore, organisms in the stem group of a phylum can possess the "body plan" of the phylum without all the characteristics necessary to fall within it.[clarification needed] This weakens the idea that each of the phyla represents a distinct body plan.[10]

A classification using this definition may be strongly affected by the chance survival of rare groups, which can make a phylum much more diverse than it would be otherwise[clarification needed]. Representatives of many modern phyla did not appear until long after the Cambrian.[clarification needed][11]

Known phyla[edit]

Animal phyla[edit]

Protostome Bilateria
Others (Radiata or Parazoa)
Phylum Meaning Common name Distinguishing characteristic Species described
Acanthocephala Thorny headed worms Thorny-headed worms Reversible spiny proboscis that bears many rows of hooked spines approx. 1,100
Acoelomorpha Without gut Acoels No mouth or alimentary canal (alimentary canal = digestive tract in digestive system) approx. 350
Annelida Little ring Annelids Multiple circular segment 17,000+ extant
Arthropoda Jointed foot Arthropods Segmented bodies and jointed limbs, with Chitin exoskeleton 1,134,000+
Brachiopoda Arm foot Lamp shells Lophophore and pedicle 300-500 extant
Bryozoa Moss animals Moss animals, sea mats Lophophore, no pedicle, ciliated tentacles, anus outside ring of cilia 5,000 extant
Cnidaria Stinging nettle Anemones / Jellyfish Nematocysts (stinging cells) approx. 11,000
Gastrotricha Hair stomach Hairybacks Two terminal adhesive tubes approx. 690
Gnathostomulida Jaw orifice Jaw worms approx. 100
Micrognathozoa Tiny jaw animals Accordion-like extensible thorax 1
Mollusca Soft Mollusks / molluscs Muscular foot and mantle round shell 112,000[12]
Nematoda Thread like Round worms Round cross section, keratin cuticle 25,000–1,000,000[13][14]
Nematomorpha Thread form Horsehair worms approx. 320
Nemertea A sea nymph Ribbon worms approx. 1,200
Phoronida Zeus's mistress Horseshoe worms U-shaped gut 11
Placozoa Plate animals Differentiated top and bottom surfaces, two ciliated cell layers, amoeboid fiber cells in between 1
Platyhelminthes Flat worm Flatworms approx. 25,000[15]
Porifera* Pore bearer Sponges Perforated interior wall 5,000+ extant
Priapulida Little Priapus approx. 16
Rhombozoa Lozenge animal Single anteroposterior axial cell surrounded by ciliated cells 75
Rotifera Wheel bearer Rotifers Anterior crown of cilia approx. 2,000
Tardigrada Slow step Water bears Four segmented body and head 1,000+
Xenacoelomorpha Strange flatworm Ciliated deuterostome 2
Total: 35 2,000,000+

Land plant phyla (divisions)[edit]

The ten Divisions into which the living embryophytes (land plants) are often placed are shown in the table below. To these may be added two algal Divisions, Chlorophyta and Charophyta, which are included with land plants in the clade Viridiplantae (see also current definitions of Plantae). The definition and classification of plants at this level varies from source to source and has changed progressively in recent years. Thus some sources place horsetails in division Arthrophyta and ferns in division Pteridophyta,[16] while others place them both in Pteridophyta, as shown below. The division Pinophyta may be used for all gymnosperms (i.e. including cycads, ginkgos and gnetophytes),[17] or for conifers alone as below.


Division Meaning Common name Distinguishing characteristics
Anthocerotophyta[19] Anthoceros-like plants hornworts horn-shaped sporophytes, no vascular system
Bryophyta[20] Bryum-like plants, moss plants mosses persistent unbranched sporophytes, no vascular system


Marchantia-like plants

liver plants

liverworts ephemeral unbranched sporophytes, no vascular system


Lycopodium-like plants

"wolf" plants

clubmosses & spikemosses microphyll leaves, vascular system
Pteridophyta[citation needed] Pteris-like plants, fern plants ferns & horsetails prothallus gametophytes, vascular system
Pinophyta,[citation needed]


Pinus-like plants

cone-bearing plants

conifers cones containing seeds and wood composed of tracheids
Cycadophyta[24] Cycas-like plants, palm-like plants cycads seeds, crown of compound leaves
Ginkgophyta[25] Ginkgo-like plants ginkgo, Maidenhair tree seeds not protected by fruit (single living species)
Gnetophyta[26] Gnetum-like plants gnetophytes seeds and woody vascular system with vessels
Magnoliophyta Magnolia-like plants flowering plants, angiosperms flowers and fruit, vascular system with vessels
Total: 10

Fungal divisions[edit]

Main article: Fungi
  1. Chytridiomycota
  2. Blastocladiomycota
  3. Zygomycota
  4. Glomeromycota
  5. Ascomycota
  6. Basidiomycota
  7. Microsporidia
  8. Neocallimastigomycota

Protista phyla (Divisions)[edit]

Group Description Phylum[27] Meaning Common name Distinguishing characteristics Example
Heterotrophs (no locomotor apparatus) Rhizopoda root-foot[28] Amoeba Amoeboids have the ability to change their shape. Amoeba
Actinopoda ray-foot ------- long, thin axopodia Radiolarians
Foraminifera hole bearers Forams Complex shells with one or more chambers Forams
Photosynthetic protists Dinoflagellata whirling scourge Dinoflagellates Unicellular, have two dissimilar flagella Red tides
Euglenophyta Good-eyed plant Euglenids Have a pellicle, which gives shape to the cell. Euglena
Chrysophyta golden plant golden algae Diatoma
Rhodophyta rose plant red algae Cells do not have flagella or centrioles; use phycobiliproteins which gives red tint Coralline Algae
Phaeophyta gray plant brown algae chloroplasts surrounded by four membranes - form differentiated tissues Kelp
Heterotrophs (flagella) Sarcomastigophora Trypanosoma cruzi
Ciliophora Paramecium
Non-motile spore-formers Apicomplexa Plasmodium
Heterotrophs (restricted mobility) Oomycota Water Molds
Acrasiomycota Dictyostelium
Myxomycota Fuligo
Total: 14

Bacterial phyla/divisions[edit]

Main article: Bacterial phyla

Currently there are 29 phyla accepted by List of Prokaryotic names with Standing in Nomenclature (LPSN)[29]

  1. Acidobacteria, phenotipically diverse and mostly uncultured
  2. Actinobacteria, High-G+C Gram positive species
  3. Aquificae, only 14 thermophilic genera, deep branching
  4. Bacteroidetes
  5. Caldiserica, formerly candidate division OP5, Caldisericum exile is the sole representative
  6. Chlamydiae, only 6 genera
  7. Chlorobi, only 7 genera, green sulphur bacteria
  8. Chloroflexi, green non-sulphur bacteria
  9. Chrysiogenetes, only 3 genera (Chrysiogenes arsenatis, Desulfurispira natronophila, Desulfurispirillum alkaliphilum)
  10. Cyanobacteria, also known as the blue-green algae
  11. Deferribacteres
  13. Dictyoglomi
  14. Elusimicrobia, formerly candidate division Thermite Group 1
  15. Fibrobacteres
  17. Fusobacteria
  18. Gemmatimonadetes
  19. Lentisphaerae, formerly clade VadinBE97
  20. Nitrospira
  21. Planctomycetes
  23. Spirochaetes, species include Borrelia burgdorferi, which causes Lyme disease
  24. Synergistetes
  25. Tenericutes, alternatively class Mollicutes in phylum Firmicutes (notable genus: Mycoplasma)
  26. Thermodesulfobacteria
  27. Thermomicrobia
  28. Thermotogae, deep branching
  29. Verrucomicrobia

Archaeal phyla/division/kingdoms[edit]

  1. Crenarchaeota, Second most common archaeal phylum
  2. Euryarchaeota, most common archaeal phylum
  3. Korarchaeota
  4. Nanoarchaeota, ultra-small symbiotes, single known species
  5. Thaumarchaeota

See also[edit]


  1. ^ The term was coined by Haeckel from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan."


  2. ^ Berg, Linda R. (2007-03-02). Introductory Botany: Plants, People, and the Environment (2 ed.). Cengage Learning. p. 15. ISBN 9780534466695. Retrieved 23 July 2012. 
  4. ^ Valentine 2004, p. 8.
  5. ^ Naik, V.N. (1984). Taxonomy of Angiosperms. Tata McGraw-Hill. p. 27. ISBN 9780074517888. 
  8. ^ Rouse G.W. (2001). "A cladistic analysis of Siboglinidae Caullery, 1914 (Polychaeta, Annelida): formerly the phyla Pogonophora and Vestimentifera". Zoological Journal of the Linnean Society 132 (1): 55–80. doi:10.1006/zjls.2000.0263. 
  10. ^ Budd, G. E. (1998). "Arthropod body-plan evolution in the Cambrian with an example from anomalocaridid muscle". Lethaia (Blackwell Synergy) 31 (3): 197–210. doi:10.1111/j.1502-3931.1998.tb00508.x. 
  14. ^ Zhang, Z (2013). "Animal biodiversity: An update of classification and diversity in 2013. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013)". Zootaxa 3703 (1): 5–11. doi:10.11646/zootaxa.3703.1.3. 
  15. ^ Species Register. "Flatworms — Phylum Platyhelminthes". Marine Discovery Centres. Retrieved 2007-04-09. 
  16. ^ Mauseth 2012, pp. 514, 517.
  17. ^ a b Cronquist, A.; A. Takhtajan; W. Zimmermann (1966). "On the higher taxa of Embryobionta". Taxon (International Association for Plant Taxonomy (IAPT)) 15 (15): 129–134. doi:10.2307/1217531. JSTOR 1217531. 
  20. ^ a b Mauseth 2012, p. 489.
  22. ^ Mauseth 2012, p. 509.
  23. ^ Mauseth 2012, p. 535.
  24. ^ Mauseth 2012, p. 540.
  25. ^ Mauseth 2012, p. 542.
  26. ^ Mauseth 2012, p. 543.
  27. ^
  28. ^
  29. ^ J.P. Euzéby. "List of Prokaryotic names with Standing in Nomenclature: Phyla". Retrieved 30 December 2010. 

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