1	Saprobic or, if parasitic or predacious, having mycelium immersed in the host tissue	(Zygomycetes) 2
	Associated with arthropods and attached to the cuticle or digestive tract by a holdfast and not immersed in the host tissue	(Trichomycetes) 39
2 (1)	Mycelium ± regularly septate, septa with plugs; zygospores, where known, formed on undifferentiated hyphae	3
	Mycelium, septa and zygospores not as above	4
3 (2)	Merosporangia bispored, septal plugs with polar protuberance, dissolving in 2-3% KOH	(Dimargaritales) Dimargaritaceae
	Merosporangia unispored, septal plugs without polar protuberance, not dissolving in KOH	(Kickxellales) Kickxellaceae
4 (2)	Sporangia or 'conidia' forcibly released, or if not forcibly released then non-haustorial parasites of cicadas or nematodes with the latter producing two or more pedicellate, globose, spinose 'conidia' terminally and laterally from a coenocytic, erect pedicel	5
	Sporangia not forcibly released; if non-haustorial parasites of nematodes spores formed in chains or if solitary, not both globose and spinose; fertile hyphae often septate at maturity	6
5 (4)	Sporangiophore arising from trophocyst; sporangia multispored, thallus mycelial	(Mucorales, p.p.) 11
	Sporangiophore not arising from trophocyst; 'conidia' few- or unispored; thallus mycelial or consisting of hyphal bodies or protoplast-like cells	(Entomophthorales, p.p.) 28
6 (4)	Spores formed in sporocarps produced in soil or on organic material above ground, saprobes or ecto- or endomycorrhizal; or spores formed singly in soil, endomycorrhizal and forming arbuscules in roots of phycobiont	7
	Spores not formed as above; saprobes or parasites	10
7 (6)	Sporocarps formed	8
	Sporocarps not formed, spores formed singly in soil	(Glomales, p.p.) 33
8 (7)	Sporocarps containing only multispored sporangia	(Mucorales, p.p.) 11
	Sporocarps containing zygospores, azygospores or chlamydospores	9
9 (8)	Only zygospores present in sporocarp; saprobes or ectomycorrhizal	(Endogonales) Endogonaceae
	Sporocarps containing azygospores or chlamydospores; endomycorrhizal	(Glomales, p.p.) 33
10 (6)	Saprobes or facultative parasites; sporangiospores formed in sporangia, sporangiola, or less commonly merosporangia; arthrospores, chlamydospores and/or yeast-like cells sometimes present	(Mucorales, p.p.) 11
	Obligate haustorial or non-haustorial parasites of fungi or small animals or their eggs; sporangiospores formed in multispored or unispored merosporangia; chlamydospores sometimes formed	(Zoopagales) 35
11 (5)	Sporangia ± lageniform, multispored; sporangiospores hyaline, smooth-walled, without appendages	12
	Sporangia usually globose to obpyriform, never lageniform	13
12 (11)	Sporangia formed singly or in pairs; rhizoides present	Saksenaeaceae
	Sporangia borne verticellately; rhizoids absent	Mucoraceae (p.p.)
13 (11)	Sporangia formed in a sporocarp	Mortierellaceae (p.p.)
	Sporangia not formed in a sporocarp	14
14 (13)	Uni- or multispored merosporangia produced on a fertile vesicle	Syncephalastraceae
	Merosporangia not produced; sporangia and/or sporangiola present	15
15 (14)	Sporangiospores fusiform to broadly fusiform, often with hyaline, hair-like, polar appendages; sporangia non-apophysate, wall persistent, fracturing regularly into 2 or irregularly into 3-4 segments by a preformed suture	16
	Sporangiospores not with the above combination of characters, usually smooth-walled, rarely ornamented or appendaged; sporangium wall deliquescent' if persistent fracturing irregularly; sporangia sometimes absent and only sporangia produced	17
16 (15)	Sporangiospore wall pale brown to reddish-brown; sporangia only or sporangia and sporangiola (on separate sporangiophores) produced; orange pigment (carotene) usually produced in mycelium on rich media; zygosporangium smooth, thin, hyaline; zygospore reddish-brown, wall striate; suspensors apposed	Choanephoraceae (p.p.)
	Sporangiospore wall hyaline; sporangia only produced; mycelium hyaline; zygosporangium verruculose, blackish-brown; suspensors opposed	Gilbertellaceae
17 (15)	Sporangia uni- to multi-spored, acolumellate (columella-like structure septum-like or dome-shaped, never protruding into the sporangium); mycelium usually extremely fine	Mortierellaceae
	Not with the above combination of characters; sporangia columellate; sporangiola columellate or acolumellate, sometimes arising from a vesicle; mycelium more robust	18
18 (17)	Sporangia never formed; sporangiola uni- or multispored, pedicellate, arising from a fertile vesicle	19
	Sporangia formed; sometimes sporangiola also present	24
19 (18)	Fertile vesicles produced from primary vesicles present on uniseptate sporangiophore branch; uni- or multi-spored pedicellate or denticulate, acolumellate sporangiola present; zygospores where known smooth-walled, suspensors with appendages	Radiomycetaceae
	Not with the above combination of characters; fertile vesicles produced terminally on the sporophore or its branches or on a lateral vesicle; sporangiola columellate or acolumellate; sterile spines sometimes present	20
20 (19)	Sporangiola columellate, uni- or multi-spored; saprophytic or gall-forming mycoparasites; sporophore sometimes bearing sterile spines	21
	Sporangiola acolumellate, uni- or multi-spored; sterile spines on sporophore absent	22
21 (20)	Sporangiola uni-spored; sporophore bearing sterile spines	Chaetocladiaceae
	Sporangiola multi-spored; sterile spines on sporophore absent	Thamnidiaceae (p.p.)
22 (20)	Sporangiospore wall pale brown to reddish-brown, striate; zygospores with apposed suspensors	Choanephoraceae (p.p.)
	Sporangiospore wall hyaline, smooth or spinose; zygospore with opposed suspensors	23
23 (22)	Sporophore mostly branched; fertile vesicles terminal and lateral; sporangiola uni-spored, pedicel monomorphic, sporangiospores released by random fracture of the pedicel and/or dissolution of the sporangiolar wall; yeast-like cells absent	Cunninghamellaceae
	Sporophore simple or rarely once or twice branched; fertile vesicles terminal; sporangiola uni- or multispored, pedicel mono- or dimorphic, sporangiospores released by fracture of the pedicel at preformed cicumscissile zone, sporangiolum wall persistent, separable from the sporangiospore wall; yeast-like cells produced after spore germination on rich media	Mycotyphaceae
24 (18)	Deliquescent sporangia and persistent-walled sporangiola present	Thamnidiaceae (p.p.)
	Only sporangia produced, either with persistent or deliquescent wall	25
25 (24)	Sporangia ± apophysate	Mucoraceae (p.p.)
	Sporangia non-apophysate; sporophore sometimes vesiculate or constricted below the sporangium	26
26 (25)	Sporangium wall blackish-brown to black, persistent; trophocyst sometimes produced; subsporangial vesicle sometimes produced, globose or broadly ellipsoid; sporangium liberated whole by collapse of the subsporangial vesicle or by cicumscissile rupture of the junction between the sporangium wall and the sporophore, or sometimes forcibly discharged; zygospore usually yellowish, suspensors apposed, zygosporangium thin, hyaline	Pilobolaceae
	Sporangium liberation not as described above; subsporangial vesicles absent or small and hemispherical and then with a deliquescent sporangium; zygospore suspensors opposed or tongs-like	27
27 (26)	Sporophore unbranched, usually bluish-green; zygospore suspensors tongs-like, with branched appendages	Phycomycetaceae
	Sporophore branched or unbranched, never bluish-green; zygospore suspensors opposed, without appendages	Mucoraceae (p.p.)
28 (5)	Nuclei large, >10 µm long, not staining with aceto-orcein, with a prominent nucleolus; sporophores with a vesicle subtending the spore ('conidium'); gametangia, if present, with small, beak-like accessory cells; contents of secondary spores and somatic hyphae in some species may divide ad produce small protoplast-like cells (appearing multispored); all cells uninucleate	Basidiobolaceae
	Nuclei small, < 10 µm long, aceto-orcein nuclear staining and nucleolus visibility variable; sporophores without a subtending vesicle; gametangia, if present, without accessory cells; spores and mycelium not producing internal protoplast-like cells; cells not all uninucleate	29
29 (28)	Nuclei variable, 2-15 µm long during interphase, with much heterochromatin (staining readily in aceto-orcein and bismark brown); nucleolus not prominent; nucleus remaining visible during mitosis	Entomophthoraceae
	Not as above	30
30 (29)	Nuclei relatively large (> 5 µm long), nucleoplasm appearing granular (chromatin condensed at interphase); sporophores short and unbranched, arising from sporogenous cells; spores forcibly discharged by papillar eversion; obligate intracellular parasites of fern gametophytes	Completoriaceae
	Nuclei 2-5 µm long, with little heterochromatin (not staining in aceto-orcein or bismark brown), usually inconspicuous during mitosis; nucleolus prominent; spores discharged by papillar eversion, fluid discharge, or passively released; saprobes or parasites of insects, freshwater algae or soil invertebrates	31
31 (30)	Sporophores upright, simple, each bearing several spores; parasitic on soil invertebrates (nematodes and tardigrades)	Meristacraceae
	Sporophores usually unbranched, one spore borne terminally; saprobes or parasites of insects, soil invertebrates, freshwater algae or causing mycotic infections of animals	32
32 (31)	Spores (asexual spores and zygospores) tending to be melanized (pale grey to black); zygospores budding from conjugation point of two hyphal bodies; obligate parasites of mites and insects (esp. Homoptera)	Neozygitaceae
	Spores hyaline; zygospores formed in axis of parential hyphae as a result of conjugation between adjacent cells or scalariform conjugations between two hyphae; saprobes or obligate parasites of desmid algae, soil invertebrates, or facultative mycotic disease agents of animals	Ancylistaceae
33 (7)	Only arbuscules formed in mycorrhizal roots; azygospore-like bodies formed at the apex of sporogenous cells of fertile hyphae; auxiliary cells present	Gigasporaceae
	Arbuscules and vesicles formed in mycorrhzal roots; chlamydospores formed terminally and laterally on or within fertile hyphae; auxiliary cells absent	34
34 (33)	Chlamydospores formed apically	Glomaceae
	Chlamydospores formed from within the neck of a sporiferous saccule	Acaulosporaceae
35 (10)	Spores solitary, short pedicellate, formed on the surface of a vesicle or sessile and formed in pairs or chains from the coiled apex of a sporophore; spores of some taxa large, brown	36
	Spores solitary (unispored) or in chains (multispored) and borne in merosporangia, long or short pedicellate, or sessile, or arising from a head-cell or a secondary branchlet, if arising from a vesicle usually multispored; unispored merosporangia not large and brown; sporophore apex not coiled	37
36 (35)	Fertile hyphae several times dichotomously branched, septate, terminating in sterile spines; fertile vesicles pedicellate, arising in pairs from the cell at the branching point of the fertile hyphae; spores ± hyaline, relatively small; parasites of fungi	Sigmoideomycetaceae
	Fertile hyphae simple, coenocytic, without sterile spines; sporophore apex forming a fertile vesicle or not swollen and coiled; spores brown, large; parasites of microfauna or their eggs	Helicocephalidaceae
37 (35)	Haustorial mycoparasites, especially of Mucorales	Piptocephalidaceae
	Haustorial ectoparasites or non-haustorial endoparasites of soil microfauna	38
38 (37)	Predacious, with adhesive material on hyphae to trap prey; vegetative mycelium formed outside host	Zoopagaceae
	Ecto- or endoparasitic; vegetative mycelium within host, only sporophores formed outside host	Cochlonemataceae
39 (1)	Spores (trichospores) produced exogenously, usually bearing one or more basal appendages; zygospores produced in most genera	(Harpellales) 40
	Spores (sporangiospores) or amoeboid cells produced endogenously, or thallus breaking up into arthrospores; zygospores not present	41
40 (39)	Thallus unbranched, usually attached to the peritrophic membrane of the midgut (less common to the hindgut cuticle)	Harpellaceae
	Thallus branched, attached to the hindgut cuticle	Legeriomycetaceae
41 (39)	Thallus branched and septate, producing arthrospores	(Asellariales) Asellariaceae
	Thallus unbranched, or branched only at the base; non-septate; producing sporangiospores or amoeboid cells	42
42 (41)	No amoeboid cells; sporangiospores usually produced singly in basipetal series of terminal sporangia	(Eccrinales) 43
	Amoeboid cells produced at some stage; entire thallus functioning as sporangium, releasing spores or amoeboid cells more or less simultaneously	(Amoebidiales) Amoebidiaceae
43 (42)	Thalli producing directly only one type of spore; sporangia sometimes germinating in situ	Palavasciaceae
	Thalli usually producing at least two types of spores; sporangia not germinating in situ	44
44 (43)	Primary infestation spores produced in thalli that become converted entirely or partly into multispored sporangia	Parataeniellaceae
	Primary infestation spores produced singly in series of terminal sporangia	Eccrinaceae