Main Content

The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Systematics of Protozoa

We thank following scientists and The Society of Protozoologists (The Journal of Protozoology) for quoting text descriptions from their papers.

1. The Subkingdom PROTOZOA

Systematic analysis; Mainly morphology.

2. The Kingdom PROTOZOA

Systematic analysis; Molecular phylogenetics.

3. Protist diversity

Systematic analysis; Ultrastructural identity.
David J. Patterson, 1999 (ref. ID; 5694)


(The International Commission on Zoological Nomenclature) 1985: International Code of Zoological Nomenclature. Berkeley, Los Angeles

History of Classification

ref. ID; 4925, 4978, 5694, 5695

1. The Subkingdom Protozoa

[ref. ID; 923]

The Committee on Systematics and Evolution of The Society of Protozoologists
N.D. Levine (Chairman); J.O. Corliss; F.E.G. Cox; G. Deroux; J. Grain; B.M. Honigberg; G.F. Leedale; A.R. Loeblich, III; J. Lom; D. Lynn; E.G. Merinfeld; F.C. Page; G. Poljansky; V. Sprague; J. Vavra; and F.G. Wallace

The first Protozoa were seen by Antony van Leeuwenhoek in 1674. Linnaeus included 2 species of free-living Protozoa in the 1758 edition of his System Naturae, but he included no parasitic ones. At present, over 65,000 protozoan species (of which over half are fossil and ~10,000 are parasitic) have been named. Among living species, this includes ~250 parasitic and 11,300 free-living sarcodines (of which ~4,600 are Foraminiferida); ~1,800 parasitic and 5,100 free living flagellates; ~5,600 parasitic "Sporozoa" (including Apicomplexa, Microspora, Myxospora, and Ascetospora); and ~2,500 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more species still unnamed. The classical taxonomic scheme of the Protozoa was developed about the turn of the century. In it they were considered a phylum and were divided into 2 subphyla, Plasmodroma (containing the classes Mastigophora, Sarcodina, and Sporozoa) and Ciliophora. This scheme was based primarily on organelles of locomotion. In 1964 the Society of Protozoologists introduced a new but fairly similar classification. It is remarkable how many important and necessary changes have been made in the classification since 1964. Every major group has been affected. The 1964 scheme was a necessary step in the development of the present one, but it is now obsolete. One of the principal sources of many new data of taxonomic significance has been electron microscopy.

As in the Society's 1964 Classification, phyla, subphyla, and superclasses end in "-a"; classes in "-ea"; subclasses in "-ia"; orders in "-ida"; and suborders in "-ina"; superorders, not used in the previous scheme, end in "-idea." These uniform endings conform to those recommended by Pearse (1936) and employed by Hall (1953) and Jahn & Jahn (1949); they differ from the more precise but longer rending suggested by Levine (1959). In general, the nomenclatural policies of this Committee are also essentially the same as those adopted by the authors of the 1964 scheme. Thus, a worker who originally proposed a new name at any level lower than that of suborder is not credited with the name of the new higher taxon, even if essentially the same word is used for it or even if the new taxon (e.g. order or class) contains only a single family. The responsibility for the name of the high-level taxon (suborder or above) is that of the person who established its actual level and its concept. The same situation obtains when a given higher taxon, e.g. an order, has been elevated to another level, e.g. a class, with retention of the original taxon (order)- the name of the higher taxon (class) is credited to the worker who created it. On the other hand, if a group, originally established at the class or subclass level, is now considered to contain several more recently created orders, one of which bears a name similar to that of the class or subclass, the authority and date of the name of either of the latter taxa is automatically employed for this order, with different authorships and dates of the others; the same procedure applies to suborders with in an order. While this Classification is the product of a committee, it should not be assumed that its every member, although responsible for his own group, is in agreement with the entire scheme. Indeed, probably none of them agrees with it completely; however, unanimity can hardly be expected. What were have produced is something with which we can live and which we can modify as suggested by our differing needs and ideas.

The Society's 1980 Classification

Phylum I. SARCOMASTIGOPHORA Honigberg & Balamuth, 1963

Single type of nucleus, except in heterokaryotic FORAMINIFERIDA; sexuality, when present, essentially syngamy; flagella, pseudopodia or both types of locomotor organelles. (See: ref. ID; 1663)

Subphylum I. MASTIGOPHORA Diesing, 1866

One or more flagella typically present in trophozoites; asexual reproduction basically by intrakinetal (symmetrogenic) binary fission; sexual reproduction known in some groups. (See: ref. ID; 3731)

Class 1. PHYTOMASTIGOPHOREA Calkins, 1909

Typically with chloroplasts; if chloroplasts lacking, relationship to pigmented forms clearly evident; mostly free-living. (See: ref. ID; 7291)

Order 1. CRYPTOMONADIDA Senn, 1900

Two subequal flagella arising subapically in ventral groove; chloroplasts brown, red, olive-green, blue or yellow; storage products starch and fat; cells flattened, naked, without wall or pellicle; flagellates, coccoid unicells and palmellae; sexual reproduction unknown.
Genus: Cryptomonas

Order 2. DINOFLAGELLIDA Butschli, 1885

Two heterodynamic flagella, inserted apically or laterally, one ribbon-shaped with paraxial rod and single row of fine hairs, other smooth or with 2 rows of stiffer hairs; chloroplasts typically golden-brown or green; storage product starch and fat; cells flattened or of complex symmetry with transverse and ventral grooves and often armor of cellulosic plates; nucleus unique among eukaryotes in having chromosomes that consist primarily one of nonprotein-complexed DNA; mitosis intranuclear; flagellates, coccoid unicells, colonies, and simple filaments; sexual reproduction present.
Genus: Ceratium, Gymnodinium, Prorocentrum

Order 3. EUGLENIDA Butschli, 1884

Two (rarely more) flagella, one or both emerging from an anterior invagination of the cell; emergent flagella with single row of fine hairs; flagella with paraxial rods; chloroplasts grass-green, absent in many general storage products; paramylon, fat, and cyclic metaphosphates; cell with helical symmetry, naked but with complex pellicle of interlocking proteinaceous strips; nonspindle intranuclear mitosis; flagellates or colonies. (See: ref. ID; 4226)

Order 4. CHRYSOMONADIDA Engler, 1898

Two unequal flagella, one directed anteriorly and bearing 2 opposite rows of mastigonemes, other trailing and smooth; chloroplasts golden-brown or absent; storage products chrysolaminarin and fat; cells naked, with richly patterned silicified scales, or with lorica; sexual reproduction present.
Genus: Dinobryon, Ochromonas, Synura

Order 5. HETEROCHLORIDA Pascher, 1912

Two unequal flagella; chloroplasts yellow-green; storage products oil and possibly chrysolaminarin; supposedly related to xanthophycean algae.
Genus: Chloramoeba, Heterochloris

Order 6. CHLOROMONADIDA Klebs, 1892

Two heterokont flagella; chloroplasts green; storage product oil; characteristic ring of Golgi bodies at anterior end; sexual reproduction by fusion of 2 flagellates.
Genus: Chattonella, Vacuolaria

Order 7. PRYMNESIIDA Hibberd, 1976

Two equal or subequal, smooth flagella inserted laterally or anteriorly, with unique 3rd appendage, the haptonema, between them; chloroplasts golden-brown; storage products chrysolaminarin (?) and fat; cells covered with delicate organic scales of diagnostic pattern; scales calcified to form coccoliths in coccolithophorids; sexual reproduction present.
Genus: Chrysochromulina, Coccolithus, Prymnesium

Order 8. VOLVOCIDA France, 1894

Two or 4 equal, smooth, apical flagella; chloroplasts grass-green; storage products starch and fat; sexual reproduction present.
Genus: Chlamydomonas, Volvox

Order 9. PRASINOMONADIDA Christensen, 1962

One, 2, 4, or 8 flagella, typically covered with rows of finely patterned scales; chloroplasts grass-green; storage product starch; cells typically covered with one or more layers of intricately patterned Golgi-derived scales; sexual reproduction present.
Genus: Mesostigma, Prasinomonas

Order 10. SILICOFLAGELLIDA Borgert, 1891

One flagellum; chloroplasts golden-brown or green-brown; storage product apparently chrysolaminarin; with star-shaped siliceous skeleton composed of tubular elements; sexual reproduction unknown.
Genus: Dictyocha

Class 2. ZOOMASTIGOPHOREA Calkins, 1909

Chloroplasts absent; one to many flagella; ameboid forms, with or without flagella, in some groups; sexuality known in few groups; a polyphyletic group. (See: ref. ID; 7291, 7293)

Order 1. CHOANOFLAGELLIDA Kent, 1880

One flagellum, inserted apically, with proximal part surrounded by ring of tentacles (collar); with membranous sheath or basket-like lorica composed of siliceous costae; stalked or free-swimming; free-living.
Genus: Monosiga

Order 2. KINETOPLASTIDA Honigberg, 1963 emend. Vickerman, 1976

One or 2 flagella arising from depression; flagella typically with paraxial rod in addition to axoneme; single mitochondrion (nonfunctional in some forms) extending length of body as single tube, hoop, or network of branching tubes, usually containing conspicuous Feulgen-positive (DNA-containing) kinetoplast (nucleoid) located near flagellar kinetosomes; Golgi apparatus typically in region of flagellar depression, not connected to kinetosomes and flagella; parasitic (majority of known species) and free-living.

Order 3. PROTEROMONADIDA Grasse, 1952 emend. Vickerman, 1976

One or 2 pairs of heterodynamic flagella without paraxial rods; single mitochondrion, distant from kinetosomes, curing around nucleus, not extending length of body, without Feulgen-positive kinetoplast; Golgi apparatus encircling band-shaped rhizoplast passing from kinetosomes near surface of nucleus to mitochondrion; cysts present; parasitic.
Genus: Karotomorpha, Proteromonas

Order 4. RETORTAMONADIDA Grasse, 1952

Two to 4 flagella, one turned posteriorly and associated with ventrally located cytostomal area bordered by fibril; mitochondria and Golgi apparatus absent; intranuclear division spindle; "semiopen'" mitosis reported from 1 genus; cysts present; parasitic.
Genus: Chilomastix, Retortamonas

Order 5. DIPLOMONADIDA Wenyon, 1926 emend. Brugerolle, 1975

One or 2 karyomastigonts; genera with 2 karyomastigonts with two-fold rotational symmetry or, in one genus, primarily mirror symmetry; individual mastigonts with 1 to 4 flagella, typically one of them recurrent and associated with cytostome, or, in more advanced genera, with organelles forming cell axis; mitochondria, and Golgi apparatus absent; intranuclear division spindle; "semiopen" mitosis reported in one genus; cysts present; free-living or parasitic.

Order 6. OXYMONADIDA Grasse, 1952

One or more karyomastigonts, each containing 4 flagella typically arranged in 2 pairs in motile stage; one or more flagella may be recurrent, adhering to body surface for greater or lesser distance; kinetosomes of flagellar pairs connected by paracrystalline structure ("preaxostyle") in which are embedded anterior ends of axostylar microtubules; one to many axostyles per organism, contractile in many genera; mitochondria and Golgi apparatus (including Janicki-type parabasal apparatus) absent; division spindle intranuclear; cysts in some species; sexuality in some species; parasitic.
Genus: Monocercomonoides, Oxymonas, Pyrsonympha

Superorder 1. PARABASALIDEA Honigberg, 1973

[Notice] This superorder was proposed by Honigberg to include TRICHOMONADIDA Kirby and HYPERMASTIGIDA Grassi & Foa, which share several important characters and which must have had common ancestry. Since, on the basis of the presently available information, no other zoomastigophorean orders can be considered as closely related as the trichomonads and hypermastigotes, there appears no justification for establishment of other superorders within this class. Although this procedure does not conform to the commonly accepted usage, I consider the inclusion of the single superorder in the present scheme consistent with our attempt to indicate degrees of interrelationships among the higher taxa wherever possible.

Typically at least some kinetosomes, bearing flagella or barren, arranged in pattern and associated with rootlet filaments characteristic of trichomonads; one or more argentophilic Janicki-type parabasal apparatuses (Golgi complexes applied to filaments with Type A periodicity) present; mitochondria absent; division spindle extranuclear.

Order 7. TRICHOMONADIDA Kirby, 1947 emend. Honigberg, in Camp, Mattern & Honigberg, 1974

Typically karyomastigonts with 4 to 6 flagella, but with only 1 flagellum in one genus and no flagella in another; karyomastigonts and akaryomastigonts in one family with permanent polymonad organization; in mastigont(s) of typical genera one flagellum recurrent, free or with proximal or entire length adherent to body surface; undulating membrane, if present, associated with adherent segment of recurrent flagellum; pelta and noncontractile axostyle in each mastigont, except for one genus; hydrogenosomes present; true cysts infrequent, known in very few species; all or nearly all parasitic.
Genus: Dientamoeba, Histomonas, Monocercomonas, Trichomonas

Order 8. HYPERMASTIGIDA Grassi & Foa, 1911

Mastigont system with numerous flagella and multiple Janicki-type parabasal apparatus; "privileged" barren kinetosomes, resembling in arrangement kinetosomes of trichomonads and associated with rootlet filaments characteristic of these flagellates, present in many genera; flagella-bearing kinetosomes distributed in complete or partial circle, in plate or plates, or in longitudinal or spiral rows meeting in a centralized structure; one nucleus per cell; cysts in some species; sexuality in some species; all parasitic.

Subphyllum II. OPALINATA Corliss & Balamuth, 1963

Numerous cilia in oblique rows over entire body surface; cytostome absent; nuclear division acentric; binary fission generally interkinetal (symmetrogenic); known life cycles involve syngamy with anisogamous flagellated gametes; all parasitic.

Class 1. OPALINATEA Wenyon, 1926

With characters of the subphylum.

Order 1. OPALINIDA Poche, 1913

With characters of the class.
Genus: Opalina

Subphyllum III. SARCODINA Schmarda, 1871

Pseudopodia, or locomotive protoplasmic flow without discrete pseudopodia; flagella, when present, usually restricted to developmental or other temporary stages; body naked or with external or internal test or skeleton; asexual reproduction by fission; sexuality, if present, associated with flagellate or, more rarely, ameboid gametes; most species free-living.

Superclass 1. RHIZOPODA von Siebold, 1845

Locomotion by lobopodia, filopodia, or reticulopodia, or by protoplasmic flow without production of discrete pseudopodia. (See: ref. ID; 4598, 5753)

Class 1. LOBOSEA Carpenter, 1861

Pseudopodia lobose or more or less filiform but produced from broader hyaline lobe; usually uninucleate; multinucleate forms not flattened or much-branched plasmodia; no sorocarps, sporangia, or similar fruiting bodies.

Subclass 1. GYMNAMOEBIA Haeckel, 1862

Without test. (See: ref. ID; 6796)

Order 1. AMOEBIDA Ehrenberg, 1830

Typically uninucleate; mitochondria typically present; no flagellate stage. (See: ref. ID; 7594, 7615)

Order 2. SCHIZOPYRENIDA Singh, 1952

Body with shape of monopodial cylinder, usually moving with more or less eruptive, hyaline, hemispherical bulges; typically uninucleate, nuclear division promitotic; temporary flagellate stages in most species. (See: ref. ID; 7594, 7755)
Genus: Naegleria, Tetramitus, Vahlkampfia

Order 3. PELOBIONTIDA Page, 1976

Body with shape of thick cylinder; monopodial, with true bidirectional fountain flow of cytoplasm common; typically multinucleate; lacking mitochondria but with symbiotic bacteria; in microaerobic habitats; no flagellate stage known, but numerous nonmotile cils visible at fine-structural level, with variations of usual microtubular pattern.
Genus: Pelomyxa

Subclass 2. TESTACEALOBOSIA De Saedeleer, 1934

Body enclosed by test, tectum, or other complex membrane external to plasma membrane and glycocalyx.

Order 1. ARCELLINIDA Kent, 1880

Test, tectum, or other external membrane with single aperture and composed of either organic or inorganic material or both. (See: ref. ID; 6790, 7745)
Genus: Arcella, Cochliopodium, Difflugia

Order 2. TRICHOSIDA Mobius, 1889

Test composed of fibrous sheath and, in at least one extensive stage of life cycle, with calcareous spicules, and multiple apertures through which short, conical pseudopodia extend; locomotion by broad lobopodium; marine
Genus: Trichosphaerium

Class 2. ACARPOMYXEA Page, 1976

Small plasmodia or much-expanded similar uninucleate forms, usually branching, sometimes forming reticulum of coarse branches advancing tips lobose; no regular reversal of streaming; no test; no spores or fruiting bodies known.

Order 1. LEPTOMYXIDA Pussard, 1973

Typically thin sheets, often polyaxial; sometimes more cylindrical, limax-like forms; cysts produced by soil and freshwater species. Genus: Leptomyxa, Rhizamoeba

Order 2. STEREOMYXIDA Grell, 1966

Marine ameboid organism with more or less branched pseudopodia producing only very slow motion or serving as floating organelles.
Genus: Corallomyxa, Stereomyxa

Class 3. ACRASEA Schroter, 1886

Uninucleate amebae with eruptive, lobose pseudopodia; amebae aggregating to form pseudoplasmodium which gives rise to fruiting bodies without stalk tube; flagellate cells known in only one species; sexuality unknown.

Order 1. ACRASIDA Schroter, 1886

With characters of the class.
Genus: Acrasis

Class 4. EUMYCETOZOEA Zopf, 1884

Myxamebae with filiform subpseudopodia; flagella, when present nonmastigonemate, in unequal, less often equal, apical pair; producing aerial fruiting bodies; stalk tube typically present in fruiting bodies of first 2 subclasses and in some members of 3rd.

Subclass 1. PROTOSTELLIA Olive & Stoianovitch, 1966

Trophic stage varying from single amebae to plasmodia which lack shuttle streaming; flagellate cells present or absent; fruiting bodies consisting of one to several spores on narrow, hollow stalk; sexuality known in one species.

Order 1. PROTOSTELIIDA Olive & Stoianovitch, 1966

With characters of the subclass.
Genus: Ceratiomyxa, Protostelium

Subclass 2. DICTYOSTELIIA Lister, 1909

Amebae aggregate of form multicellular pseudoplasmodium that gives rise to multispored fruiting body stalk tube present no flagellate cells; sexuality indicated in some species.

Order 1. DICTYOSTELIIDA Lister, 1909

With characters of the subclass.
Genus: Dictyostelium

Subclass 3. MYXOGASTRIA Fries, 1829

Major trophic stage multinucleate plasmodium typically with shuttle streaming; fruiting bodies multispored; flagellate cells present; syngamy and meiosis in life cycle.

Order 1. ECHINOSTELIIDA Martin, 1961

Sporangia stalked, minute; plasmodium small, ameba-like, nonreticulate.
Genus: Echinostelium

Order 2. LICEIDA Lister, 1909

Spore mass usually light-colored; lime usually absent from sporocarps; true capillitium lacking; pseudo-capillitum often present.
Genus: Licea

Order 3. TRICHIIDA Masse, 1892

Spore mass usually light-colored; lime usually absent from sporocarps; true capillitium present.
Genus: Trichium

Order 4. STEMONITIDA Masse, 1892

Spore mass usually dark-colored; lime, when present, restricted to substrate, stipe, and columella.
Genus: Stemonitis

Order 5. PHYSARIDA Masse, 1892

Spore mass usually dark-colored; peridium and/or capillitium calcareous.
Genus: Physarum

Class 5. PLASMODIOPHOREA Cook, 1928

Obligate intracellular parasites with minute plasmodia; zoospores produced in zoosporangia and bearing anterior pair of unequal, nonmastigonemate flagella; resting spore formed in compact sori of loose clusters within host cells; sexuality reported in some species.

Order 1. PLASMODIOPHORIDA Cook, 1928

With characters of the class.
Genus: Plasmodiophora, Sorosphaera

Class 6. FILOSEA Leidy, 1879

Hyaline, filiform pseudopodia, often branching, sometimes anastomosing; no spores or flagellate stage known. (See: ref. ID; 4224)

Order 1. ACONCHULINIDA De Saedeleer, 1934

Without external skeletal material; filopodia produced from main mass of cell, not from hyaline lobe.
Genus: Nuclearia, Vampyrella

Order 2. GROMIIDA Claparede & Lachmann, 1859

Body enclosed by test or rigid external membrane with distinct aperture.
Genus: Euglypha, Gromia

Class 7. GRANULORETICULOSEA De Saedeleer, 1934

Delicate, finely granular or hyaline reticulopodia or, rarely, finely pointed, granular but nonanastomosing pseudopodia.

Order 1. ATHALAMIDA Haeckel, 1862

Genus: Arachnula, Biomyxa

Order 2. MONOTHALANMIDA Haeckel, 1862

With single-chambered organic or calcareous test, sometimes including foreign matter; no alternation of generations.
Genus: Liberkuehnia

Order 3. FORAMINIFERIDA D'Orbigny, 1826

Test with one to many chambers; pseudopodia protruding from aperture, wall perforations or both; reproduction with alternation of sexual and asexual generations, of which one may be secondarily repressed; gametes usually flagellate, rarely ameboid; nuclear dimorphism in developmental stages of some species.

Class 8. XENOPHYOPHOREA Schulze, 1904

Multinucleate plasmodium enclosed in branched-tube system composed of transparent organic substance; numerous barite crystals in cytoplasm; fecal pellets retained outsides organic tube system as conspicuous dark masses; test of foreign matter surrounding tube system and fecal-pellet masses; marine.

Order 1. PSAMMINIDA Poche, 1913

Without linellae (threads forming part of test); body more or less rigid.
Genus: Psammetta, Psammina

Order 2. STANNOMIDA Tendal, 1972

With linellae (threads forming part of test); body flexible.
Genus: Stannophyllum

Superclass 2. ACTINOPODA Calkins, 1909

Often spherical, usually planktonic; axopodia with microtubular stereoplasm; skeleton, when present, composed of organic matter and/or silica, or else of strontium sulfate; reproduction asexual and/or sexual; trophic cells rarely flagellated; in many species small flagellated stages whose exact nature (gametes or spores) is still usually uncertain.

Class 1. ACANTHAREA Haeckel, 1881

Strontium surface skeleton, usually composed of 20 radial or 10 diametral spines oriented according to Muller's Law, rarely 16 diametrical or 32 radial spines oriented according to Haeckel's Law; sometimes many more spines randomly oriented; spines more or less joined in cell center extracellular outer (cortex) and inner envelops usually present; inner envelope (called "capsular membrane") often closely lining central cell mass; marine, usually planktonic.

Order 1. HOLACANTHIDA Schewiakoff, 1926

Usually 10, sometimes 16 diametral spines, crossing in center; inner envelope far outside central cell mass, or absent; encystment before sporogenesis, at least in several species.
Genus: Acanthochiasma, Acanthocolla, Acanthoplegma

Order 2. SYMPHYACANTHIDA Schewiakoff, 1926

Twenty radial spines totally fused in cell center or forming there small sphere by apposition of their basal pyramids; inner envelop far outside central cell mass; encystment before sporogenesis, at least in some species.
Genus: Acantholithium, Amphilithium, Pseudolithium

Order 3. CHAUNACANTHIDA Schewiakoff, 1926

Twenty radial spines with bases more or less loosely articulated; inner envelop at some distance outside central cell mass, or absent; encystment before sporogenesis in most or perhaps all species.
Genus: Conacon, Gigartacon, Stauracon

Order 4. ARTHRACANTHIDA Schewiakoff, 1926

Usually 20 radial spines joined at cell center by apposition of bases; inner envelope usually closely lining central cell mass; no cysts.

Order 5. ACTINELIIDA Haeckel, 1885

Variable number of radial spines, not disposed according to Muller's Law; mostly planktonic, one benthic genus.
Genus: Actinelius, Astrolophus, Podactinelius

Class 2. POLYCYSTINEA Ehrenberg, 1838

Siliceous skeleton present in most species; made up usually of solid elements, consisting of one or more latticed shell with or without radial spines, or of one or more isolated spicules; capsular membrane composed usually of grossly polygonal plates and containing many more than 3 pores; axonemes often originating from axoplast in endoplasm; marine, planktonic.

Order 1. SPUMELLARIDA Ehrenberg, 1875

Capsular membrane with uniformly distributed pores.

Order 2. NASSELLARIDA Ehrenberg, 1875

Capsular membrane with pores gathered at a single pole; skeleton of one piece, often basket-shaped.
Genus: Eucoronis, Plagiacantha, Plagonium

Class 3. PHAEODAREA Haeckel, 1879

Skeleton (sometimes absent) of mixed silica and organic matter, consisting of usually hollow spines and/or shells; very thick capsular membrane with astropyle (functioning as cytopharynx) at one pole; 2 smaller parapylae, penetrated by axopodia, usually at other pole; ectoplasm with phaeodium (group of dark corpuscles and debris); marine, planktonic.

Order 1. PHAEOCYSTIDA Haeckel, 1879

Skeleton absent, or consisting of spicules either free or radiating from common junction point.
Genus: Astracantha, Aulacantha, Phaeodina

Order 2. PHAEOSPHAERIDA Haeckel, 1879

Skeleton consisting mainly of very large latticed shell with wide polygonal meshes.
Genus: Aulosphaera, Cannosphaera, Sagosphaera

Order 3. PHAEOCALPIDA Haeckel, 1887

Skeleton consisting mainly of small shell, usually with numerous pores, often with one large opening; shell texture usually porcellanous, sometimes alveolar, never diatomaceous; radial spines often present.
Genus: Castanella, Circoporus, Tuscarora

Order 4. PHAEOGROMIDA Haeckel, 1879

Skeleton consisting mainly of small diatomaceous or alveolar shell with one large opening; shell, sometimes greatly reduced, may bear spines.
Genus: Atlanticella, Challengeron, Medusetta

Order 5. PHAEOCONCHIDA Haeckel, 1879

Skeleton consisting of 2 thick, usually hemispherical valves pressed against each other.
Genus: Concharium, Conchopsis, Neosphaeroconchidium

Order 6. PHAEODENDRIDA Haeckel, 1908

Skeleton consisting of 2 noncontiguous valves, from which originate long, branching spines with ramifications that may produce enormous external latticed spongious shells.
Genus: Coelodendrum, Coelographis, Coelothamnus

Class 4. HELIOZOEA Haeckel, 1866

Without central capsule; skeletal structures, if present, siliceous or organic; axopodia radiating on all sides; most species freshwater, some marine. (See: ref. ID; 3960, 7656, 7737)

Order 1. DESMOTHORACIDA Hertwig & Lesser, 1874

Cell enclosed in usually spherical, latticed organic capsule stalked in most species; no centroplast; microtubular stiffening elements, not discernible as axonemes, present in axopodia of some species; uni- or diflagellate zoospores.
Genus: Clathrulina

Order 2. ACTINOPHRYIDA Hartmann, 1913

No skeleton; no centroplast or axoplast; microtubular stiffening elements of axopodia usually discernible as axonemes by light microscopy; some with flagella or flagellated stage; sexuality known in some genera.
Genus: Actinophrys, Actinospharium, Ciliophrys

Order 3. TAXOPODIDA Fol, 1883

Bilaterally symmetrical, planktonic cells with siliceous spines; swimming by rowing action of axopodia arranged in parallel longitudinal rows; axopodia insert on complex, thick nucleotheca; small biflagellated species; marine.
Genus: Sticholonche

Order 4. CENTROHELIDA Kuhn, 1926

Frequently with a skeleton of siliceous plates and/or spines or of organic spicules; with centroplast or axoplast on which axonemes insert or, if centroplast absent, with large, eccentric nucleus; microtubular elements of axopodia frequently discernible by light microscopy as axonemes; some species with flagella or flagellated stages. (See: ref. ID; 4884)
Genus: Acanthocystis, Gymnosphaera, Raphidiophrys


[Notice] LABYRINTHOMORPHA phyl. n. was created by F.C. Page, with the diagnosis given in the body of this classification.

Trophic stage, ectoplasmic network with spindle-shaped or spherical, nonameboid cells; in some genera ameboid cells move within network by gliding; with sagenogenetosome, unique cell-surface organelle, associated with ectoplasmic network; heterokont zoospores produced by most species; saprobic and parasitic on algae, mostly in marine and estuarine waters.

Class 1. LABYRINTHULEA Levine & Corliss, 1963

With characters of the phylum.

Order 1. LABYRINTHULIDA Lankester, 1877

With characters of the class.
Genus: Labyrinthula, Thraustochytrium

Phylum III. APICOMPLEXA Levine, 1970

All species parasitic.

Phylum IV. MICROSPORA Sprague, 1977

Obligatory intracellular parasites in nearly all major animal groups.

Phylum V. ASCETOSPORA Sprague, 1978

All species parasitic.

Phylum VI. MYXOZOA Grasse, 1970 emend.

All species parasitic.

Phylum VII. CILIOPHORA Doflein, 1901

[Notice] The present classification of CILIOPHORA is a compromise between that of Corliss (1977) and that of de Puytorac et al. (1974). Publications, some 4 to 6 years ago suggested revolutionary changes in the concepts and bases for classification of the ciliates over the essentially Faurean scheme. Although, for the most part, the French and American proposals differed rather little, some additional refinements and/or criticisms have been made since the time of the original schemes, and still newer data have been accumulating. Thus, the Committee's ciliatologists have been faced with the formidable task of finding a single agreeable "compromise" classification for the present paper. To meet such a need and yet recognize the legitimacy of significant differences of opinion, footnotes have been used throughout this section-they generally contain comments of greatest value to specialists on the systematics of the groups concerned. In general, spellings of taxonomic names and data on authorships and dates conform to those used in Corliss (1977, 1979), except for the slight modification, here, of the suffixes on class and subclass names.

Simple cilia or compound ciliary organelles typical in at least one stage of life cycle; with subpellicular infraciliature present even when cilia absent; 2 types of nuclei, with rare exception; binary fission transverse, basically homothetogenic and generally parakinetal, but budding and multiple fission also occur; sexuality involving conjugation, autogamy, and cytogamy, nutrition heterotrophic; contractile vacuole typically preset; most species free-living, but many commensal, some truly parasitic, and large number found as symphorionts on variety of "hosts". (See: ref. ID; 1663, 4132)

Class 1. KINETOFRAGMINOPHOREA de Puytorac, Batisse, Bohatier, Corliss, Deroux, Didier, Dragesco, Fryd-Versavel, Grain, Groliere, Hovasse, Iftode, Laval, Roque, Savoie & Tuffrau, 1974

[Notice] Because of the large number of authors responsible for the names of this and some of the other ciliophoran taxa included in the present classification, all the author's names are given only once, in connection with the first name of their authorship cited in this scheme. Subsequently, this "authority" is referred to as "de Puytorac et al., 1974".

Oral infraciliature only slightly distinct from somatic infraciliature and differentiated from anterior parts, or other segments, of all or some of somatic kineties; stomatogenesis generally telokinetal; cytostome often apical (or subapical) or mid-ventral, on surface of body or at bottom of atrium or vestibulum; cytopharyngeal apparatus commonly prominent; compound ciliature, oral or somatic, typically absent.

Subclass 1. GYMNOSTOMATIA Butschli, 1889

Cytostomal area superficial, apical or subapical; circumoral infraciliature without kinetosomal differentiation other than closer packing of kinetosomes, insertion of supplementary segments of kineties, or pairing (not as dyads) of kinetosomes; cytopharyngeal apparatus of rhabdos type toxicysts common; somatic ciliation usually uniform.

Order 1. PROSTOMATIDA Schewiakoff, 1896

Cytostome apical or subapical; circumoral infraciliature involving anterior parts of all somatic kineties; typical polyploid independent macronucleus; body often large; commonly carnivorous.

Order 2. PLEUROSTOMATIDA Schewiakoff, 1896

Cytostome slit-like, lateral; circumoral infraciliature including anterior parts of only few somatic kineties and showing differentiation into left and right components; body often large, laterally compressed; macronucleus possibly of low ploidy number; voracious carnivores. (See: ref. ID; 7355)
Genus: Amphileptus, Litonotus, Loxophyllum

Incertae sedis in subclass GYMNOSTOMATIA

[Notice] The Incertae sedis category is used here advisedly, although with some reluctance. The problem of a homokaryotic ciliate has been complicated by preliminary findings in an ultrastructural (as yet unpublished) study of Stephanopogon - a number of its characteristics appear to be significantly flagellate -like! In the case if the karyorelictids, which French workers generally place in the order PLEUROSTOMATIDA, the location of Geleia has become particularly controversial: Nouzarede (1977) has recently created a new order for it, the PROTOHETEROTRICHIDA (not included in the present scheme), in the class POLYHYMENOPHORA.

Order PRIMOCILIATIDA Corliss, 1974

Nuclei homokaryotic, with prominent RNA-rich nucleolus or endosome; cytostome apical, slit-like; somatic ciliature sparse, ventral; small, marine benthic forms, thigmotactic, often algivorous.
Genus: Stephanopogon

Order KARYORELICTIDA Corliss, 1974

Macronucleus diploid (with possible exceptions) and nondividing; fragile, highly thigmotactic; oral area apical or ventral slit; somatic toxicysts; postciliodesmata characteristically present; contractile vacuoles absent; mainly interstitial sand-dwelling forms, often carnivorous. (See: ref. ID; 4875)
Genus: Geleia, Kentrophoros, Loxodes, Trachelocerca

Subclass 2. VESTIBULIFERIA de Puytorac et al., 1974

Apical or near-apical (occasionally at posterior pole) vestibulum commonly present, equipped with cilia derived from anterior parts of somatic kineties (normal or reorganized) and leading to cytostome; stomatogenesis sometimes involving 2 anlagen; cytopharyngeal apparatus resembling rhabdos; free-living or parasitic, especially in digestive tract of vertebrates and invertebrates.

Order 1. TRICHOSTOMATIDA Butschli, 1889

No reorganization of somatic kineties at level of vestibulum other than more packed alignment of kinetosomes or addition of supernumerary segments of kineties; many species endocommensals in vertebrate hosts.

Order 2. ENTODINIOMORPHIDA Reichenow, in Doflein & Reichenow, 1929

Oral and somatic ciliature functioning as syncilia; somatic ciliature in form of unique ciliary tufts of bands, otherwise body naked; oral area sometimes retractable; pellicle generally firm, sometimes drawn out into processes; skeletal plates in many species; stomatogenesis apokinetal; commensals in mammalian herbivores, including anthropoid apes.
Genus: Cycloposthium, Entodinium, Ophryoscolex, Troglodytella

Order 3. COLPODIDA de Puytorac et al., 1974

Vestibular ciliature and infraciliature highly organized by reorganization of parts of somatic kineties in vestibulum, but stomatogenesis basically telokinetal (sometimes involving 2 anlagen); body often contorted, rendering morphogenetics of division complex; somatic kinetids typically with kinetosomes in pairs; cysts common; mostly free-living, often in edaphic habitats. (See: ref. ID; 4692, 7466 (Grossglockneriids), 7537, 7706)
Genus: Colpoda, Platyophrya, Tillina, Woodruffia

[Notice] Platyophrya: Grain (in Dragesco et al., 1977) has recently proposed a new order, PLATYOPHRYIDA (in a superorder PLATYOPHRYIDEA), for this problematic genus and several alleged relatives (e.g., Cyrtolophosis and Woodruffia), placing it as the most primitive group in the subclass HYPOSTOMATA. Such a taxonomic arrangement, although endorsed by McCoy (1978) and others, is not followed here, awaiting further data with regard to the ultrastructure of the cytopharyngeal apparatus, especially.

Subclass 3. HYPOSTOMATIA Schewiakoff, 1896

[Notice] French workers (de Puytorac & Grain 1976, de Puytorac et al. 1974) have insisted on insertion of superordinal taxa among the several orders comprising this large subclass of kinetofragminophorans; these are adapted here, except for PLATYOPHRYIDEA and SUCTORIDEA, although Corliss (1977, 1979) maintains that they are of limited taxonomic value at the present state of our knowledge. The most striking and most extensive changes in the present ciliate scheme over that of the Society's earlier classification are to be seen among the groups here assembled under the HYPOSTOMATIA-dozens of significant papers have been published on them within the past 10-20 years, one of the most heuristic being Faure-Fremiet's (1967) succinct but perceptive contribution.

Cytostome nonpolar, on ventral surface; body cylindrical or flattened dorsoventrally, often with reduction of somatic ciliature; cytopharyngeal apparatus typically of cyrtos type; oral area may be sunk into atrium, with atrial ciliature present; morphogenesis often complex, with stomatogenesis of advanced telokinetal type or even para- or buccokinetal-like; some species astomatous free-living or ecto- or endocommensals, principally of invertebrates.

Superorder 1. NASSULIDEA Jankowski, 1967

[Notice] Two suborders, the SYNHYMENIIA and the NASSULOPSINA, have been recognized by some workers as comprising this order, following the original proposal of de Puytorac et al. (1974); but Corliss (1979) and others believe that more data are needed firmly to establish such a suprafamilial separation.

Hypostomial frange of many pats, running obliquely across anterior end of ventral surface, or extremely reduced to few adoral "pseudomembranelles" (sometimes in oral atrium); body often cylindrical, with complete somatic ciliature; cyrtos of numerous nematodesmata; free-living, most often in freshwater habitats.

Order 1. SYNHYMENIIDA de Puytorac et al., 1974

Parts of generally extensive hypostomial frange more or less fused (= synhymenium); kineties bipolar; body often cylindrical, with complete ciliation; stomatogenesis parakinetal-like. (See: ref. ID; 7403)
Genus: Nassulopsis, Orthodonella, Scaphidiodon

Order 2. NASSULIDA Jankowski, 1967

Parts of hypostomial frange individualized, limited to left side of ventral surface, sometimes reduced to few "pseudomembranelles", distinct preoral suture; stomatogenesis para- or buccokinetal-like.

Superorder 2. PHYLLOPHARYNGIDEA de Puytorac et al., 1974

Cyrtos complex, embedded in foliated or laminated phagoplasm; commonly relatively few but distinctive nematodesmata, often partly recurved, with "teeth-like" capitula; circumoral ciliature restricted to 3 short rows of kinetosomes near oral opening; somatic ciliature only on ventral surface, in 2 dissymmetric fields; preoral suture skewed to left; macronucleus commonly heteromerous.

Order 1. CYRTOPHORIDA Faure-Fremiet, in Corliss, 1956

Three rows of oral ciliature arising from kineties of left field, composed of pairs of kinetosomes with inverted polarity; body dorsoventrally flattened or laterally compressed; ventral ciliature often thigmotactic; many species with "glandular" adhesive organelle near posterior end.

Order 2. CHONOTRICHIDA Wallengren, 1895

Variously vase-shaped, sessile and sedentary forms; naked, except for ciliature of ventral surface (displaced to apical end of body); cytopharynx without nematodesmata; adhesive organelle active in stalk production; macronucleus heteromerous; reproduction by budding; marine and freshwater species, ectocommensal principally on crustaceans.

Superorder 3. RHYNCHODEA Chatton & Lwoff, 1939

Aberrant, small rostrate forms, with sucking tube and toxicysts; body of mature stage often nearly naked or with somactic ciliature limited to thigmotactic field; buds or "larvae" typically ciliated (in 2 fields); commensal or pathogenic, most commonly on gills of marine bivalves.

Order 1. RHYNCHODIDA Chatton & Lwoff, 1939

With characters of the superorder.
Genus: Ancistrocoma, Gargarius, Sphenophrya

Superorder 4. APOSTOMATIDEA Chatton & Lwoff, 1928

Cytostome inconspicuous or, in certain stages of polymorphic life cycle, absent; glandular complex (rosette) typically near oral area; in mature forms somatic ciliature spiraled, often widely space; commonly anterior thigmotactic ciliary field; stomatogenesis specialized, derived from telokinetal type; life cycle complex, sometimes involving alternation of hosts (unique in phylum); palintomy and cysts common; most species associated with marine crustaceans.

Order 1. APOSTOMATIDA Chatton & Lwoff, 1939

With characters of the superorder.

Subclass 4. SUCTORIA Claparede & Lachmann, 1858

[Notice] The SUCTORIA present at least 2 problems: (a) whether or not they should be considered taxonomically closer to the hypostomes [by incorporation there as a separate superorder, as originally suggested by de Puytorac et al. (1974) and (b) whether or not the order SUCTORIDA should be composed of 2 [after Corliss 1977), 3 [after Corliss 1979], or 7[after Batisse 1975] distinct suborders. The generally more conservative positions have been taken here; i.e., the subclass has been considered deserving a separate status at the subclass level (many workers have made the separation at even higher ranks; see reviews in Corliss 1968, 1979) and the number of suborders has been placed at the intermediate figure of 3 (formerly, none has been recognized).

Suctorial tentacles, generally multiple (polystomy), containing haptocysts; adult body sessile and sedentary, seldom with cilia; reproduction by budding; stalk commonly present, noncontractile, produced by scopuloid; conjugation of the involving micro- and macroconjugants; migratory larva ciliated (with right field and possibly vestigial left field), without tentacles or stalk; widespread on marine and freshwater organisms, occasionally endocommensal.

Order 1. SUCTORIDA Claparede & Lachmann, 1858

With characters of the subclass.

Class 2. OLIGOHYMENOPHOREA de Puytorac et al., 1974

Oral apparatus, at least partially in buccal cavity, generally well defined, although absent in one group; oral ciliature, clearly distinct from somatic ciliature, consisting of paroral membrane (stichodyad) on right side and small number of compound organelles (membranelles, peniculi, or polykineties) on left side; stomatogenesis parakinetal or buccokinetal; cytostome usually ventral and/or near anterior end, present at bottom of buccal or influndibular cavity; cysts not uncommon; various species loricate; colony-formation common in some groups. (See: ref. ID; 3915, 4125)

Subclass 1. HYMENOSTOMATIA Delage & Herouard, 1896

[Notice] Some workers (e.g., see Lynn et al. 1978) would elevate the hymenostomatid suborder PENICULINA of ordinal status, very likely a good idea (but arriving too late for detailed consideration by the Committee). French specialist (e.g., see de Puytorac et al. 1974, 1976) suggest amalgamation of the 2nd and 3rd scuticociliated suborders, with others (see Corliss 1979) arguing for their separation; all 3 orders are tentatively retained here.

Body ciliation often uniform and heavy; buccal cavity, when present, ventral; kinetodesmata regularly present, usually conspicuous; sessile forms and stalk, colony, and cyst formation relatively rare; freshwater forms predominant.

Order 1. HYMENOSTOMATIDA Delage & Herouard, 1896

Buccal cavity well defined, containing membranelles or peniculi with infraciliary bases typically 3-4 rows of kinetosomes wide; oral area on ventral surface, usually in anterior half of body; no scutica appearing during stomatogenesis.

Order 2. SCUTICOCILIATIDA Small, 1967

Body uniformly to sparsely ciliated; thigmotactic area common in many species buccal ciliature often dominated by tripartite (anterior, middle, and posterior segments) paroral membrane on right side; mucocysts, director-meridian, and caudal cilia common; stomatogenesis buccokinetal, with appearance of prominent unique scutica during morphogenesis; mitochondria long, interkinetal, sometimes fused to form gigantic "chondriome"; no nematodesmata and probably no trichocysts; cysts common. (See: ref. ID; 7213)

Order 3. ASTOMATIDA Schewiakoff, 1896

Body usually large or long, uniformly ciliated; mouth absent; complex infraciliary endoskeleton and often elaborate holdfast organelles (hooks, spines, or sucker) may be present at anterior end; silverline system resembling that of hymenostomatids; fission may be by budding, with chain-formation; cytoproct absent; contractile vacuoles present; all endoparasitic, mostly in oligochaetes (soil, freshwater, marine); few species in other annelids, molluscus, and turberllarians; one major group in caudate amphibians.
Genus: Anoplophrya, Cepedietta, Intoshellina, Radiophrya

Subclass 2. PERITRICHIA Stein, 1859

Oral ciliary field prominent, covering apical end of body and dipping into infundibulum; paroral membrane, generally called "haplokinety", and adoral membranelles, "polykineties", becoming "peniculi" in infundibulum present; somatic ciliature reduced to temporary posterior circlet of locomotor cilia; stomatogenesis buccokinetal; widely distributed species, many stalked and sedentary, others mobile, all with aboral scopula; dispersal by migratory telotroch (larval form); mucocysts and pellicular pores universal; myonemes associated with strong contractility of stalk or parts of body; conjugation total, involving fusion of micro- and macroconjugants.

Order 1. PERITRICHIDA Stein, 1859

With characters of the subclass.

Class 3. POLYHYMENOPHOREA Jankowski, 1967

[Notice] Several taxonomic problems remain unresolved at this time. Is Bursaria no longer to be recognized as a heterotrich [see the startling announcement by Fernandez-Galiano (1978)]? Should the order OLIGOTRICHIDA be raised to (a 2nd) subclass in the class? Is Strobilidium more properly assigned to the tintinnines than the oligotrichines? Should the hypotrichs be subdivided into more than 2 suborders? But some very important changes over earlier "spirotrich" classifications are agreed on: for example, (a) removal of the entodiniomorphids to the VESTIBULIFERIA, of class KINETOFRAGMINOPHOREA [following findings of Grain (1969), Noirot-Timothee (1969), and Wolska (1971)]; (b) recognizing 6 separate suborders of heterotrichs [based especially on works of Albaret (1974) and Jankowski (1964, 1967)]; (c) clarifying problems within the oligotrich and hypotrich taxa [see Borror (1972), Deroux (1974), Faure-Fremiet (1970), Faure-Fremiet & Ganier (1970), Grain (1972), Laval (1973), Radoicic (1969), Remane (1969), Tappan & Loeblich (1968) and Tuffrau (1972)].

Dominated by well-developed, conspicuous adoral zone (AZM) of numerous buccal or peristomial organelles (para- or heteromembranelles), often extending out onto body surface; on right side, one or several lines of "paroral" ciliature (mono- or diplo- or poly-stichomonads or pairs of kinetosomes); stomatogenesis parakinetal or apokinetal; somatic ciliature complete or reduced, or appearing as cirri; cytostome at bottom of buccal cavity or infundibulum; somatic infraciliature rarely including kinetodesmata; postciliodesmata common and prominent; cytoproct often absent; cyst, and especially loricae, very common in some groups; often large and commonly free-living, free-swimming forms in great variety of habitats.

Subclass 1. SPIROTRICHIA Butschli, 1889

With characters of the class. (See: ref. ID; 4111)

Order 1. HETEROTRICHIDA Stein, 1859

Generally large to very large forms, often highly contractile, sometimes pigmented; body dominated by AZM, but also commonly bearing heavy holotrichous ciliation; macronucleus oval or, often, beaded; parasitic and free-living species.

Order 2. ODONTOSTOMATIDA Sawaya, 1940

Laterally compressed, wedge-shaped, with armor-like cuirass and often posterior spines; somatic ciliature reduced; AZM with only 8 or 9 membranelles and no paroral membrane cytoproct absent; several small species, chiefly in putrefying organic matter in freshwater habitats, few marine.
Genus: Epalxella, Mylestoma, Saprodinium

Order 3. OLIGOTRICHIDA Butschli, 1887

Body ovoid to elongate, sometimes with tail; pellicle thickened, with perilemma external to cell membrane in many species; somatic ciliature reduced; AZM (of paramembranelles) extensive, often separable into one part inside buccal cavity and another on nearby body surface; paroral membrane and its infraciliary base single (monostichomonad); stomatogenesis apokinetal; macronuclear reorganization bands present; cytoproct absent; free-swimming, macrophagous, mainly pelagic. (See: ref. ID; 4356)

Order 4. HYPOTRICHIDA Stein, 1859

Dorsoventrally flattened, highly mobile (yet often thigmotactic), with unique cursorial type of locomotion body dominated by compound ciliary structures, consisting of prominent AZM (of numerous paramembranelles) near anterior end, multiple paroral lines (diplo- or polystichomonads) on right side of peristomial field, and cirri on ventral surface; rows of widely spaced "sensory-bristle" cilia common on dorsal surface; complex fibrillar system; some species loricate, few colony-forming; stomatogenesis typically apokinetal; macronuclear reorganization bands common; species numerous and very widespread. (See: ref. ID; 3630, 4386, 4889, 7307, 7354, 7590, 7679)

2. The Kingdom Protozoa

[ref. ID; 4887 (Thomas Cavalier-Smith: 1996/97 version)]

Subkingdom EOZOA Cavalier-Smith 1996

Flagellate, amoeboflagellate or rarely amoeboid protozoa having discoid, often rigid, mitochondrial cristae or hydrogenosomes bounded by two membranes; pseudopods usually (exception Dientamoeba) eruptive.


Phylum TRICHOZOA Cavalier-Smith 1996

Flagellates or rarely amoebae with hydrogenosomes and prominent Golgi dictyosomes; closed mitosis with extranuclear mitotic spindle. Constituent subphyla: Anaeromonada, Parabasala. The name TRICHOZOA (Greek trichos = hair) is chosen because the phylum consists predominantly of trichomonads and hypermastigotes, the latter having a very hairy appearance because of their numerous long cilia.

Subkingdom NEOZOA Cavalier-Smith 1996

Diagnosis as for infrakingdom NEOZOA Cavalier-Smith 1993.

Infrakingdom SARCODINA Hertwig & Lesser 1874 stat. nov. Cavalier-Smith 1996

Amoeboid Protozoa with non-eruptive pseudopods; mitochondrial cristae usually tubular, rarely vesicular or non-rigidly discoid; axopodia absent; mitochondria and peroxisomes rarely absent, but if so without hydrogenosomes.


Superphylum EOSARCODINA Cavalier-Smith 1996

Sarcodines with granular reticulopodia or with filose pseudopods and stalked aerial fruiting bodies.

Constituent phyla: RETICULOSA, MYCETOZOA


RETICULOSA were previously included in the NEOSARCODINA, but 28S ribosomal RNA trees suggest that they are not closely related to the testaceafilosian Gromia and branch well below the megakaryote radiation near to MYCETOZOA (Pawlowski et al. 1994). Pawlowski et al. (1996) give evidence from 18S rRNA for a similar or even lower position for foraminifera, and suggest that the sequence studied by Wray et al. (1995) that groups foraminiferans with Apicomplexa may actually be from a parasite, not the foram itself. I have therefore excluded RETICULOSA from the NEOSARCODINA, and group them instead with MYCETOZOA as the new superphylum EOSARCODINA, on the assumption that their common ancestor was a tubulicristate sarcodine with an anisokont flagellate stage. Although EOSARCODINA is a paraphyletic group it is possible that the ability of pseudopodia to fuse together as reticulopodia in RETICULOSA, and for separate amoebae to fuse together to make plasmodia in the Myxogastrea, has a common mechanistic basis; such capacity for pseudopodial fusion is relatively rare in NEOSARCODINA, being found only in some chlorarachnean and LOBORETICULATIDA.

Superphylum HAPLOSPORIDA Cavalier-Smith 1996

Diagnosis as for sole constituent phylum HAPLOSPORIDIA Caullery and Mesnil, 1899 (Cavalier-Smith 1993)

Superphylum NEOSARCODINA Cavalier-Smith 1993 emend. 1996

Sarcodines with filose or lobose pseudopods but no stalked fruiting bodies; unstalked fruiting bodies or non-granular reticulopodia very rarely present.

Phylum RHIZOPODA Dujardin 1835 stat. nov. Haeckel 1866 emend. Cavalier-Smith 1995

Emended diagnosis

Amoeboflagellates with variable pseudopods or non-ciliate amoebae usually with filose pseudopods or sarcodine phase an intracellular microplasmodium; mitochondria (usually with tubular cristae) and Golgi dictyosomes present. Extrusomes often present.

Phylum AMOEBOZOA Luhe 1913 stat. nov. Corliss 1984 emend. Cavalier-Smith 1995

Emended diagnosis

Non-ciliate amoebae with lobose pseudopodia, multiciliated amoebae, or uniciliate amoebae; mitochondrial cristae tubular or mitochondria and peroxisomes absent; extrusomes absent. (See: ref. ID; 4944, 6789)

Subphylum ARCHAMOEBAE Cavalier-Smith 1983 stat. nov.

Subphylum HOLOMASTIGA subphy. nov. Cavalier-Smith 1996

Class HOLOMASTIGA cl. nov. Cavalier-Smith 1996

Multiciliated amoebae; sole order HOLOMASTIGIDA Lauterborn 1895 (as suborder HOLOMASTIGINA) and family MULTICILIIDAE Poche (HOLOMASTIGIDAE Lemmermann 1914) and genus Multicilia Cienkowski 1881.

Subphylum LOBOSA Carpenter 1861 stat. nov. Cavalier-Smith 1996

Diagnosis as for class LOBOSEA (Cavalier-Smith 1993) (See: ref. ID; 7079). Constituent classes AMOEBAEA and TESTACEALOBOSEA.

Infrakingdom ALVEOLATA Cavalier-Smith 1991

Superphylum MIOZOA Cavalier-Smith 1987

Superphylum HETEROKARYOTA Hickson 1903 stat. nov. Cavalier-Smith 1993

Infrakingdom ACTINOPODA Calkins 1902 stat. nov. Cavalier-Smith 1996

Infrakingdom and phylum NEOMONADA Cavalier-Smith 1996

Non-amoeboid aerobic flagellates with peroxisomes, mitochondria and Golgi dictyosomes; cristae tubular or flat, never discoid; cortical alveoli, rigid tubular ciliary hairs, axopodia and locomotory pseudopodia all absent; cilia 1, 2 or many, rarely (Corallochytrea) absent.


MYCETOZOA were earlier grouped with OPALOZOA (See: ref. ID; 7292) as a superphylum OPALOMYXA and this taxon was grouped with CHOANOZOA as the parvkingdom CILIOMYXA (Cavalier-Smith 1993). However these two taxa now appear to be polyphyletic according to the recent molecular trees (Cavalier-Smith & Chao 1995, 1996) and are best abandoned. However, these trees also suggest that CHOANOZOA and APUSOZOA are more closely related to each other than to any other protozoan phyla (Cavalier-Smith & Chao 1995), so I have created the phylum and infrakingdom NEOMONADA for them. Both NEOMONADA and CHOANOZOA are monophyletic taxa, but are paraphyletic because of the derivation of both the kingdoms ANIMALIA and FUNGI from choanoflagellate ancestors (Cavalier-Smith 1987). NEOMONADA are all non-amoeboid zooflagellates and, as discussed below, probably arose from a neosarcodine amoeboflagellate by the loss of the amoeboid phase. Rather than retaining phylum rank for CHOANOZOA and creating a separate phylum for the other three neomonad subphyla, I have reduced CHOANOZOA in rank to subphylum in order to include all the non-alveolate and non-amoeboid neozoan zooflagellates in a single phylum, which will be more practically useful.

Infraphylum EXTRUMONADA Cavalier-Smith 1996

Apusozoans with extrusomes.

Infraphylum EURYMONADA Cavalier-Smith 1996

Apusozoans without extrusomes.

[ref. ID; 4924 (Thomas Cavalier-Smith: 2003 version)]

These new insights have come not just from molecular sequence studies but by integrating them with numerous other lines of evidence, genetic, structural and biochemical. The classical view developed over two centuries that reliance on a single line of evidence or character is often very misleading for phylogeny and systematics is at last penetrating the previously over-dogmatic and over-self-confident field of molecular systematics.


Subkingdom: SARCOMASTIGOTA Cavalier-Smith 1993 emend.

Phylum 1: AMOEBOZOA Luhe 1913 stat. nov. Corliss 1984 emend. Cavalier-Smith 1998

(See: ref. ID; 4944)

Subphylum 1: PROTAMOEBAE+ Cavalier-Smith 2004

Subphylum 2: CONOSA Cavalier-Smith 1998

Infraphylum 1: ARCHAMOEBAE Cavalier-Smith 1983 stat. nov. 1998

Infraphylum 2: MYCETOZOA De Bary stat. nov.

Phylum 2: CHOANOZOA Cavalier-Smith 1981 emend. 1998

Subkingdom BICILIATA subkingd. nov.

Ancestrally biciliate unicellular eukaryotes in which dihydrofolate reductase and thymidylate synthase genes, if present, are fused into a single unit of translation; lacking plastids in the cytoplasm with double envelopes and lacking plastids within the rough endoplasmic reticulum or tubular ciliary hairs; mitochondrial cristae usually tubular or discoid (i.e. all bikonts excluding Plantae and Chromista).

Infrakingdom 1: RHIZARIA Cavalier-Smith 2002 emend.

(See: ref. ID; 6795)

Phylum 1: CERCOZOA Cavalier-Smith 1998 emend. 2002

(See: ref. ID; 7130)

Subphylum 1: FILOSA Cavalier-Smith 2003