Phylum

For the linguistic term, see Phylum (linguistics).

For the plant, see Phyla (genus).

Phylum (plural: phyla) is a taxon used in the scientific classification of life. "Phyla" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. Phyla represent the largest generally accepted groupings of animals and other living things with certain evolutionary traits, although the phyla themselves may sometimes be grouped into superphyla (e.g. Ecdysozoa with eight phyla, including arthropods and roundworms; and Deuterostomia with the echinoderms, chordates, hemichordates and arrow worms). Informally, phyla can be thought of as grouping animals based on general body plan, e.g., having bones vs. having an exoskeleton. This is morphological grouping. But despite the seemingly different external appearances of organisms, they are classified into phyla based on their internal organizations. For example, though seemingly divergent, spiders and crabs both belong to Arthropoda, whereas earthworms and tapeworms, similar in shape, are from Annelida and Platyhelminthes, respectively. Although the International Code of Botanical Nomenclature allows the use of the term "Phylum" in reference to plants, the term "Division" is almost always used by botanists.

The best known animal phyla are the Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata, and Chordata, the phylum humans belong to. Although there are approximately 35 phyla, these nine include the majority of the species. Many phyla are exclusively marine, and only one phylum is entirely absent from the world's oceans: the Onychophora or velvet worms. The most recently discovered phylum is Cycliophora found in 1993; only three phyla were discovered in the last century.

The Cambrian explosion was a great flowering of life forms that occurred between roughly 542 and 530 million years ago; during this time all modern phyla (and many now-extinct ones) were established. Over time the roles among different phyla have varied. For instance, during the Cambrian, the dominant megafauna, or large animals, were arthropods whereas now they are vertebrates (chordata).

Scientific classification describes the following levels of organization (taxons) for classifying life forms: Kingdom, Phylum, Class, Order, Family, Genus, Species, Subspecies. Thus Phylum is a rather broad classification. Also, the Three Domain System is now widely used and adds the level of Domain above Kingdom as the broadest classification.

List of animal phyla

Phylum	Meaning	Common name	Distinguishing characteristics	Species described
Acanthocephala	Thorny head	Thorny-headed worms	Reversible spiny proboscis	about 1,150
Acoelomorpha	Without gut	—	No mouth or alimentary canal
Annelida	Little ring	Segmented worms	Multiple circular segments	about 15,000 modern
Arthropoda	Jointed foot	Arthropods	Chitin exoskeleton	1,134,000+
Brachiopoda	Arm foot	Lamp shells	Lophophore and pedicle	between 300 and 500 extant
Bryozoa	Moss animals	Moss animals, sea mats	Lophophore, no pedicle, ciliated tentacles	about 5,000 living species
Chaetognatha	Longhair jaw	Arrow worms	Chitinous spines either side of head, fins	about 100 modern species
Chordata	Cord	Chordates	Hollow dorsal nervous chord	63,000+
Cnidaria	Stinging nettle	Coelenterates	Nematocysts (stinging cells)	about 10,000
Ctenophora	Comb bearer	Comb jellies	Eight "comb rows" of fused cilia	about 100 modern species
Cycliophora	Wheel carrying	Symbion	Circular mouth surrounded by small cilia	at least 3
Echinodermata	Spiny skin	Sea Urchins	Five-fold radial symmetry, mesodermal calcified spines	about 7,000 living species and 13,000 extinct ones
Echiura	Spine tail	Spoon worms	Set of hooks at posterior end	about 140
Entoprocta	Inside anus	Goblet worm	Anus inside ring of cilia	about 150
Gastrotricha	Hair stomach	Meiofauna	Two terminal adhesive tubes	about 450
Gnathostomulida	Jaw orifice	Jaw worms
Hemichordata	Half cord	Acorn worms	Stomochord in collar	about 100 living species
Kinorhyncha	Motion snout	Mud dragons	Eleven segments, each with a dorsal plate	about 150
Loricifera	Corset bearer	Brush heads	Umbrella-like scales at each end	about 21
Micrognathozoa	Tiny jaw animals	—	Accordion like extensible thorax	1
Mollusca	Thin shell	Mollusks / molluscs	Muscular foot and mantle round shell	about 70,000 [4]
Myxozoa	Slime animals	—	Polar capsules resembling nematocysts	at least 12,000
Nematoda	Thread like	Round worms	Round cross section, keratin cuticle	80 000 - 1 million
Nematomorpha	Thread form	Horsehair worms		about 320
Nemertea	A sea nymph	Ribbon worms		about 1200
Onychophora	Claw bearer	Velvet worms	Legs tipped by chitinous claws	about 110 modern
Orthonectida	Straight swim			about 20
Phoronida	Zeus' mistress	Horseshoe worms	U-shaped gut	20
Placozoa	Tubular animals			1
Platyhelminthes	Flat worms	Flat worms		about 25,000
Porifera	Pore bearer	Sponges	Perforated interior wall	over 5,000 modern
Priapulida	Penis	Priapulid worms	Retractable proboscis surrounded by papillae	17
Rhombozoa	Lozenge animal	—	Single axial cell surrounded by ciliated cells	75
Rotifera	Wheel bearer	Rotifers	Anterior crown of cilia	about 2000
Sipuncula	Small tube	Peanut worms	Mouth surrounded by invertible tentacles	144-320
Tardigrada	Slow step	Water bears	Four segmented body and head	about 750
Xenoturbellida	Strange flatworm	—	Ciliated deuterostome	2
TOTAL				2,400,000+

Groups formerly ranked as phyla

Name as phylum	Common name	Current consensus
Craniata	—	Subgroup of phylum Chordata; perhaps synonymous with Vertebrata.
Cephalochordata	Lancelets	Subphylum of phylum Chordata
Cephalorhyncha	—	Superphylum Scalidophora.
Enterepneusta	Acorn worms	Class of phylum Hemichordata.
Pentastomida	Tongue worms	Subclass of Maxillopoda of phylum Arthropoda.
Pogonophora	Beard worms	Part of family Siboglinidae of phylum Annelida.
Pterobranchia	—	Class of phylum Hemichordata.
Symplasma	Glass sponges	Class Hexactinellida of phylum Porifera.
Urochordata	Tunicates	Subphylum of phylum Chordata.
Vestimentifera	Vent worms	Part of family Siboglinidae of phylum Annelida.

List of plant divisions

Division	Meaning	Common name	Distinguishing characteristics
Anthophyta	Flower plant	Flowering plants	Producing flowers and fruit (or close relatives)
Bryophyta	Moss plants	Mosses & Worts	Diploid spores, no vascular system
Pteridophyta	Fern plants	Ferns	Diploid spores and vascular system
Pinophyta	Sap/pitch plants	Conifers	Cones containing seeds
Sphenophyta	Wedge plant	Horsetails	Photosynthetic, hollow, jointed and ridged stems
Cycadophyta	Palm plants	Cycads	Seeds, crown of compound leaves
Ginkgophyta	Ginkgo plants	Ginkgo, Maidenhair	Seeds not protected by fruit (single species)
Gnetophyta		Gnetophytes	Seeds and woody vascular system

List of fungi divisions

Phylum	Meaning	Common name	Distinguishing characteristics
Chytridiomycota	Little pot mushroom	Chytrids	Cellulose in cell walls, flagellated gametes
Deuteromycota	Second mushroom	Imperfect fungi	Only reproduce asexually
Zygomycota	Yoke mushroom	Zygomycetes	Blend gametangia to form a zygosporangium
Glomeromycota	Ball mushroom	None	Form arbuscular mycorrhizae with plants
Ascomycota	Bag/Wineskin Mushroom	Sac fungi	Produce spores in an 'ascus
Basidiomycota	Basidium Mushroom	None	Produce spores from a 'basidium'

External links

• Major Phyla Of Animals
• Are phyla "real"? Is there really a well-defined "number of animal phyla" extant and in the fossil record?

Etymology:

• American Heritage Dictionary: New Latin phylum, from Greek phūlon, class.
• Online Etymological Dictionary: from Gk. phylon "race, stock," related to phyle "tribe, clan," and phylein "bring forth" of physikos "pertaining to nature," from physis "nature"