Tetrapyrgos sp.
Tetrapyrgos sp.
Tetrapyrgos sp. is a tiny white forest mushroom with a black wire-thin stem, found on fallen leaves and twigs across warm regions worldwide. The label covers a genus of more than twenty accepted species rather than a single mushroom. Its spores are four-pointed, a shape unusual enough that the genus name translates roughly as "four towers".
Tetrapyrgos E. Horak 1987 — Family: Marasmiaceae (Campanellaceae in NCBI) — Order: Agaricales
Tetrapyrgos sp. is a genus-level label, used when a culture has been placed in Tetrapyrgos but not resolved to one of its species. That distinction matters here more than in most genera. The genus was created in 1987 as a replacement name, was cut down to nine species in 2015, gained six more in 2020, and gained another in 2025. Its members are small white litter agarics with a black stipe base and four-pointed spores. This guide covers what is documented for the genus, what is documented only for individual species, and where the published record is genuinely empty.
What Is Tetrapyrgos sp.?
Tetrapyrgos sp. refers to a living isolate assigned to the genus Tetrapyrgos without a species name attached. The abbreviation "sp." is standard mycological shorthand for one unidentified species inside a named genus. On a culture label it usually means the genus placement is secure while the species placement is not, and in this genus that is an honest admission rather than a shortcut. Roughly eight undescribed Tetrapyrgos lineages already sit in the NCBI sequence database under informal tags such as 'FL01', 'antipodes' and 'alboviridis'.
The mushrooms themselves are easy to overlook. A typical fruit body is a white cap under two centimetres across, sitting on a stem thinner than a pencil lead that turns grey-black to blue-black from the base upward. Cap and stem often look dusted with fine white flour. They grow on dead leaves, twigs, small fallen branches and nut shells in hardwood and mixed broadleaf forest, singly or in scattered rows, and they are saprotrophs, meaning they feed on dead plant matter rather than on a living host.
What makes Tetrapyrgos sp. worth a page of its own is the spore. The genus is defined by hyaline, inamyloid basidiospores that are distinctly tetrahedral, meaning the spores are colourless under the microscope, do not stain blue-black in iodine, and carry three to five points instead of the usual smooth ellipse. Michael Kuo describes them as triangular or jack-shaped, around eight to nine micrometres at the widest point. Under a microscope they are among the most immediately recognisable spores in the Agaricales, the order that contains most gilled mushrooms.
The rest of the generic definition is a four-part package. A Tetrapyrgos sp. has a well-developed central to off-centre stipe, a black to bluish-black stipe base seated on a small pad or disc, those tetrahedral spores, and cheilocystidia that are bulbous at the tip with a branching central axis. Cheilocystidia are sterile cells along the gill edge, and in this genus they look like tiny bottle brushes. The cap flesh and cap surface layer are not gelatinous, or only weakly so, which is the character that separates the genus from its closest relatives.
Most popular writing treats Tetrapyrgos nigripes as the core of the genus because it is the species North Americans actually find. Nomenclaturally that is wrong. The type species, the one the genus name is permanently anchored to, is Tetrapyrgos atrocyanea, described from Madagascar in 1949 and given an epitype in 2017.
Interested in this species? Out-Grow carries a liquid culture.
Tetrapyrgos sp. Liquid CultureHow Is Tetrapyrgos sp. Classified?
| Rank | Classification |
|---|---|
| Kingdom | Fungi |
| Division | Basidiomycota |
| Class | Agaricomycetes |
| Subclass | Agaricomycetidae |
| Order | Agaricales |
| Suborder | Marasmiineae |
| Family | Marasmiaceae (Index Fungorum, Species Fungorum, GBIF) or Campanellaceae (NCBI Taxonomy) |
| Genus | Tetrapyrgos E. Horak 1987 |
| Type species | Tetrapyrgos atrocyanea (Métrod) E. Horak |
| Species | 25 names in the genus, 21 currently flagged as accepted |
Tetrapyrgos naming history and the Marasmiellus synonym
Tetrapyrgos was erected by Egon Horak in Sydowia volume 39, page 101, published in 1987 on a volume dated 1986. It is a replacement name, a nomen novum, for Pterospora Métrod 1949. That earlier name was illegitimate because Pterospora Nutt. 1818 had already been used for a flowering plant. Index Fungorum carries the genus as record 25145.
The species most growers will encounter has an unusually long synonym trail. Tetrapyrgos nigripes was combined by Horak in the same 1987 paper, and GBIF lists it under seven earlier names reflecting two centuries of reshuffling. Those include Agaricus nigripes, Marasmius nigripes, Chamaeceras nigripes, Heliomyces nigripes, Pterospora nigripes and, most importantly, Marasmiellus nigripes. That last name is the one still printed on vendor labels, older field guides and herbarium slips, so a plate sold as Marasmiellus nigripes and a plate sold as Tetrapyrgos nigripes are the same fungus.
Tetrapyrgos species boundaries and the 2015 recircumscription
The single most important taxonomic paper on the genus is Honan, Desjardin, Perry, Horak and Baroni in Phytotaxa 231(2), 2015. They analysed 80 collections and 85 dried herbarium specimens across 16 species plus synonyms, and retained only nine species in Tetrapyrgos. Two were described as new, T. longicystidiata and T. parvispora, and most of the rest were moved into Campanella or left unresolved.
That contraction did not last. Komura, Oliveira and Moncalvo added six Amazonian species in Phytotaxa 440(3) in 2020, and a seventh species, T. chukeatirotei, was published in Phytotaxa 718(3) in 2025 from dead wood in a coffee plantation in Yunnan. Three of Horak's original combinations have since moved out of the genus entirely, into Metacampanella. Species Fungorum now returns 25 names for the genus with 21 flagged as accepted.
One boundary is actively contested. The 2020 Amazonian paper synonymized T. longicystidiata with the type species T. atrocyanea, but Index Fungorum has not adopted that change and still returns T. longicystidiata as a current name. Anyone working from a database rather than the primary literature will get a different answer depending on which database they open.
Tetrapyrgos family placement dispute
The family question is unsettled, and the disagreement is between major reference databases rather than between a database and a fringe opinion. Index Fungorum, Species Fungorum and GBIF all place Tetrapyrgos in Marasmiaceae. NCBI Taxonomy places it in Campanellaceae, within the suborder Marasmiineae, under genus taxid 182061.
Campanellaceae is not an informal label. It was validly published in 2024 by Oliveira, Desjardin and Moncalvo, and it appears in the 2024 fungal outline updates. Independent workers already treat Campanella, Tetrapyrgos and Metacampanella as a Campanellaceae group inside Marasmiineae. An older result adds a third option. Mata, Petersen and Hughes in 2005 recovered Tetrapyrgos inside a gymnopoid lineage alongside Lentinula, Rhodocollybia and Mycetinis, which is the assemblage that became Omphalotaceae. That 2005 tree is the origin of the occasional claim that Tetrapyrgos belongs in Omphalotaceae, and current sequence-based work does not support it.
Tetrapyrgos database identifiers
For anyone tracing a culture back to source records, the useful numbers are as follows. Index Fungorum genus record 25145. T. nigripes Index Fungorum record 131354 and GBIF taxon key 2537483, under genus key 2537457. T. atrocyanea MycoBank MB 131349 and Facesoffungi 03427. NCBI genus taxid 182061, with T. nigripes at taxid 182062.
How Do You Identify Tetrapyrgos sp.?
Identification of a Tetrapyrgos sp. runs in two stages. The field characters get you to a small white litter agaric with a blackening stem, which narrows the field considerably. The microscope then confirms the genus, because the pointed spore is the character no lookalike shares. Species-level identification is a third stage again, and usually requires sequencing.
Tetrapyrgos nigripes morphology and measurements
The type species is a different animal. T. atrocyanea has a cap 5 to 25 mm across and a stipe 10 to 36 mm long by 1 to 2 mm thick, and it is non-insititious, meaning the stem rises from a visible bluish-black mycelial pad instead of being plugged straight into a leaf. Desjardin and colleagues published full spore statistics for it, at 10 to 11.8 by 7 to 9 µm, with a mean of 11.0 by 7.9 µm and a mean length-to-width ratio of 1.41 across 20 measurements. Comparable statistics for T. nigripes have not been published.
Two microscopic characters are worth flagging as unresolved. Clamp connections, the small bridging structures found at the septa of many basidiomycete hyphae, are not confirmed present or absent for T. nigripes in any source consulted for this guide. And a 2025 paper argues that many spores in this group are truly triangular in profile rather than strictly tetrahedral, so "tetrahedral" is best read as the diagnostic tendency of the genus, not a geometric absolute.
Tetrapyrgos lookalikes and how to separate them
Marasmiellus candidus
The closest confusion in the field. Similar small white cap on similar litter, but the stipe stays white all the way to the base, while a Tetrapyrgos sp. blackens from the base up. The cap is also larger on average.
Marasmius species
Separated microscopically rather than in the field. Marasmius has a hymeniform cap surface, meaning a layer of rounded cells like a gill face, and smooth spores. A Tetrapyrgos sp. has angular pointed spores and a cutis-type cap surface.
Campanella species
Sessile or almost stemless, strongly gelatinous in cap flesh and cap surface, with ordinary ellipsoid spores. A Tetrapyrgos sp. has a well-developed stipe and non-gelatinous or only weakly gelatinous tissue.
Metacampanella olivaceonigra
Formerly placed in Tetrapyrgos and still catalogued that way in older keys. The stipe is off-centre to lateral rather than central, and the genus is sister to Tetrapyrgos rather than part of it.
Unlabelled small white agarics
No poisoning has ever been attributed to Tetrapyrgos, but small white litter mushrooms as a group include genuinely dangerous species. Nothing in this guide should be used to clear an unknown collection for eating.
Other Tetrapyrgos species
Separating species within the genus is not a field exercise. Mean ITS similarity within Tetrapyrgos is about 94.7 percent, so species calls need vouchered reference sequences rather than the nearest database match.
What a Tetrapyrgos sp. culture most likely is
On the balance of occurrence data, an unlabelled Tetrapyrgos sp. culture reaching a hobbyist in North America is overwhelmingly likely to be T. nigripes. That species accounts for 2,499 of 3,605 GBIF genus records and 5,836 of 7,737 iNaturalist genus observations, and it is the only member of the genus found on commercial offer anywhere during research for this guide. Likely is not the same as confirmed. The identification can only be settled by spore geometry plus ITS sequencing.
Where Does Tetrapyrgos sp. Grow?
Tetrapyrgos species are litter and small-wood decomposers. T. nigripes fruits on leaf litter and twigs in hardwood forest, alone or in groups. Japanese sources record it from mixed broadleaf forest on small fallen branches, fallen leaves and other dead plant material, often in rows. Other observers add wood and nut shells. The guild assignment is not guesswork. The species was included in a dedicated panel of Agaricales litter decomposers selected for genome sequencing, which is independent confirmation of how it feeds.
Tetrapyrgos substrate attachment and microhabitat
One microhabitat detail is diagnostic and easy to check. In T. nigripes the stipe base is insititious, meaning it is inserted directly into an oak leaf or twig with no basal mat of mycelium around it. Several observers note the complete absence of visible mycelial mass, although Japanese material sometimes shows black rhizomorphs, which are cord-like strands of bundled mycelium, rising alongside the fruit body. The type species behaves differently and grows from a bluish-black pad.
Tetrapyrgos geographic range
GBIF holds 3,605 occurrences for the genus, distributed very unevenly between species. T. nigripes takes 2,499 of them, followed by T. alba at 155, T. olivaceonigra at 148, T. subdendrophora at 98, T. subcinerea at 74, T. atrocyanea at 53, T. simulans at 42, T. longicystidiata at 33 and T. parvispora at 32. Most of the Amazonian and tropical species sit in single digits.
| Country | T. nigripes GBIF records |
|---|---|
| United States | 1,945 |
| French Guiana | 101 |
| Canada | 68 |
| Brazil | 56 |
| Japan | 52 |
| Costa Rica | 29 |
| Australia | 28 |
| Mexico | 26 |
| Colombia | 18 |
| Argentina | 16 |
| Scattered | India, Thailand, South Africa, China, Malaysia, Mauritius, Seychelles, DR Congo, South Korea |
Kuo describes T. nigripes as widely distributed east of the Mississippi. Japanese sources give Honshu southward, plus North and South America, and note that it is chiefly a tropical to subtropical fungus. In India it is reported as frequent in the Mangalore University botanical garden and arboretum. Texas records cluster around June and September.
Tetrapyrgos fruiting season
GBIF month facets for T. nigripes peak sharply in August with 695 records and July with 594, then fall through September at 351, October at 232 and June at 230. A long low tail across the remaining months reflects tropical collections, where seasonality is weaker. This matches summer and autumn for North America and early summer through autumn for Japan. The practical reading is that this is a warm and wet fruiter, which is a useful cue for anyone attempting to fruit it indoors. No IUCN or national red-list assessment exists for any species in the genus.
Can You Cultivate Tetrapyrgos sp.?
Tetrapyrgos sp. is not a commercially cultivated mushroom, and no peer-reviewed cultivation protocol exists for any species in the genus. That is the honest starting position, and everything below is either evidence that the fungus can be grown in pure culture or a clearly flagged vendor-grade claim. Nobody should publish or follow a confident "how to grow Tetrapyrgos" protocol, because there is no trial data underneath one.
Why Tetrapyrgos is not grown commercially
The reasons are inferential but well grounded. The fruit bodies are tiny, with caps between three millimetres and two centimetres and stems under two millimetres thick. The flesh is thin and the stipe is tough enough to resist tearing. Odour and taste are not distinctive, and Japanese reference material rates T. nigripes as unsuitable for eating. The natural substrate is thin leaf litter and twigs rather than the bulk hardwood or straw that commercial systems are built around. No yield, biological efficiency or fruiting trial figure exists for any species in the genus.
Presented honestly, that makes Tetrapyrgos sp. a culture-collector and hobbyist-mycology species rather than a food crop. It is bought to be grown on agar, studied, photographed and maintained, not harvested.
Evidence that Tetrapyrgos sp. can be grown in pure culture
The strongest evidence is institutional rather than anecdotal. T. nigripes exists as living reference strain CBS 291.85, and that strain was grown, DNA-extracted and whole-genome sequenced at Lund University as part of a litter-decomposer genome panel. A fungus that can be maintained in a public culture collection and taken to roughly 46-fold genome coverage is unambiguously culturable in vitro. The published paper defers strain handling to supplementary methods, so the specific medium, incubation temperature and growth rate used there are not on the public record.
Tetrapyrgos agar and liquid culture starting conditions
Only one real-world source describes conditions for a live Tetrapyrgos culture. An Etsy seller offers a T. nigripes plate on malt extract agar in a 90 by 15 mm dish, describes it as expandable to other plates, grain spawn and liquid cultures, names the strain "Summer", and warns that the culture is cold sensitive and should be kept at room temperature. Treat malt extract agar at room temperature as a working hypothesis, not a protocol. The cold-sensitivity claim is at least consistent with a fungus centred on tropical and subtropical latitudes, but it has not been tested in any publication.
A second useful anchor comes from outside the genus. Marasmiellus inoderma grows at 27.99 plus or minus 0.58 mm per day on malt extract agar. Because T. nigripes spent decades filed under Marasmiellus, that figure is a plausible order-of-magnitude expectation for a fast litter saprotroph. It is not a Tetrapyrgos measurement, and it should not be quoted as one.
Start on malt extract agar
Malt extract agar is the only medium a live Tetrapyrgos sp. culture has been documented on. Pour standard plates and keep a sealed master plate back as a reference.
Hold at room temperature
Do not refrigerate. The one vendor account of a live culture warns explicitly that it is cold sensitive, which implies that cold storage may kill it rather than merely slow it.
Expand into lean liquid culture
Out-Grow's general method is distilled water with light malt extract, dextrose or honey at 0.5 to 1 percent by weight, roughly 5 to 10 grams per litre, pressure sterilized in a jar with a filter and injection port.
Watch for bacterial competition
Leaner sugar is better. Residual sugar left after mycelial uptake feeds bacteria that outcompete the culture, and light malt extract keeps the broth clear enough to see contamination early.
Trial hardwood substrates
Genome work confirmed this genus carries the enzymatic toolkit for attacking lignocellulose, so supplemented hardwood is the rational substrate to test. No fruiting trial has been published.
Record everything
Colony morphology, growth rate, temperature response and medium comparison are all unpublished for this genus. A carefully logged plate experiment is genuinely novel data.
What the Tetrapyrgos sp. liquid culture is for
This liquid culture contains live mycelium of a Tetrapyrgos isolate suspended in sterile nutrient broth, ready to inoculate agar or grain. The realistic applications are agar expansion and strain maintenance, growth-rate and temperature experiments on a genus with no published cultivation data, lignocellulose and enzyme work, ITS sequencing to resolve the isolate to species, and outdoor hardwood or leaf-litter bed trials. It is not a route to a harvest, and no honest source will tell you otherwise. Liquid-culture colonization times, growth morphology and shelf life have never been published for this genus, so anything you record is new.
What Bioactive Compounds Does Tetrapyrgos sp. Contain?
No compound has been isolated from, or characterized in, any Tetrapyrgos species. There is no reported metabolite, no extract assay, no minimum inhibitory concentration, no half-maximal inhibitory concentration and no antioxidant value for the genus. This is not an oversight in this guide. It reflects the total published record.
The scale of that record explains the gap. A PubMed search for "Tetrapyrgos" returns three papers in total. One is the 2025 Metacampanella study, one is a 2016 study of fire effects on macrofungal diversity in southwest India, and one is Mata and colleagues from 2005. Three papers is an extraordinarily small footprint for a genus with more than 3,600 georeferenced occurrences.
Isolated compounds
None. No secondary metabolite has been isolated from any Tetrapyrgos species in the published literature.
Antimicrobial assays
None performed. No minimum inhibitory concentration value exists for any extract of any species in the genus.
Antioxidant assays
None performed. No DPPH radical scavenging, FRAP reducing power or total phenolic content figure has been published.
Lignocellulose enzymes
The one real chemistry-adjacent finding. Genome analysis showed T. nigripes carries the GH6, GH7, AA9 and AA3_1 cellulose-degrading gene families that white-rot fungi have and brown-rots lack.
Because the genus sat inside Marasmiellus and Marasmius for so long, it is tempting to import marasmane sesquiterpene chemistry from those relatives. Do not. Marasmane sesquiterpenes are documented from Russula foetens, drimane sesquiterpenoids from a Marasmius species, and eudesmane sesquiterpenes from Marasmiellus ramealis. All of these are findings about other genera. None is evidence about Tetrapyrgos.
Tetrapyrgos clinical evidence
There is none. A ClinicalTrials.gov query for "Tetrapyrgos" returns zero registered studies. There are no randomized controlled trials, no human pharmacokinetic data, no dosing information and no human safety data for any species in the genus. Any health claim made for a Tetrapyrgos sp. product is unsupported by definition.
Is Tetrapyrgos sp. Safe to Eat?
Treat a Tetrapyrgos sp. as inedible and cultivate it for study, not for the table. There is no published record of poisoning by any species in the genus and no toxin has been identified in it, but that absence is not a clearance.
Published edibility rating
Japanese reference material rates T. nigripes as unsuitable for eating. No mechanism, toxic compound, poisoning symptom or toxicity class is given alongside that rating.
Poisoning records
None. No poisoning by any Tetrapyrgos species appears in the literature consulted for this guide.
Toxicological testing
None performed. For a genus with three PubMed records and zero isolated compounds, the honest position is that toxicity is untested rather than absent.
Practical assessment
Fruit bodies around a centimetre across, thin flesh, tough stems and no distinctive flavour. Even if it were proven harmless, there is nothing to eat.
No reported toxicity is not evidence of safety. Kuo's account of T. nigripes carries no edibility information at all, and neither do the other field references consulted. Nothing in this guide should be used to decide that a wild collection is safe to eat, and small white litter agarics as a group include species that are not.
Tetrapyrgos traditional and medicinal use
There is no recorded traditional medicinal use, folk use or ethnomycological record for any Tetrapyrgos species, in any culture, including in the regions where the genus is common. Nothing in the sources consulted attributes medicinal, ritual, dye, tinder or food use to it anywhere in eastern North America, Japan, Amazonia or India. Given a genus that only received its current name in 1987 and that most collectors have never heard of, that silence is unsurprising rather than suspicious. Any medicinal claim encountered online for "Tetrapyrgos" should be treated as unverified and most likely transferred from Marasmius-genus marketing copy.
What Makes Tetrapyrgos sp. Remarkable?
The Tetrapyrgos four-pointed spore
The spore is the headline. Tetrapyrgos translates loosely as "four towers", and the genus is defined by hyaline, inamyloid, distinctly tetrahedral basidiospores. Field literature describes them as three to five pointed and jack-shaped, and Japanese sources call them cross-shaped and warted. Whichever description you prefer, the practical point is the same. Very few agarics produce a spore with corners, and a single microscope slide separates this genus from every white litter mushroom growing beside it.
Tetrapyrgos spore discharge and what remains untested
A Tetrapyrgos sp. is a ballistosporic agaric, meaning it actively fires its spores rather than releasing them passively. The mechanism is the standard basidiomycete surface-tension catapult. A tiny droplet forms at the spore base, nucleated by a femtomole quantity of mannitol and other sugars, and draws water from the air until it coalesces with a film on the spore surface. That sudden shift in the spore's centre of mass launches it off the sterigma at accelerations near 25,000 g, fuelled by solutes amounting to about one percent of spore mass.
What nobody has measured is what the four points do. No study has recorded discharge distance, velocity or aerodynamic behaviour for a Tetrapyrgos spore specifically, and no published work explains the function of the geometry. It is a legitimately open question, and a better answer than a fabricated aerodynamic story.
Tetrapyrgos bioluminescence claims and the evidence against them
No Tetrapyrgos species has ever been confirmed bioluminescent. The rumour probably spreads by association with luminous marasmioid relatives, and four independent surveys close it off. Desjardin and colleagues reviewed 64 luminescent species in 2008 across the Omphalotus, Armillaria and mycenoid lineages and listed none from this group. A 2024 review of 122 luminous species did not list it. A 2025 review of 132 luminous taxa did not list it either, and notably re-diagnosed two Japanese luminous Marasmiellus species as misplaced members of the Omphalotus lineage. The standing list of bioluminescent fungi includes neither Tetrapyrgos nor Campanella.
The oversized Tetrapyrgos nigripes genome
The T. nigripes CBS 291.85 assembly, GCA_013368315.1, runs to 99,142,376 base pairs in 702 contigs, released in June 2020 by Lund University. It was sequenced alongside six other Agaricales litter decomposers, and every one of those six came in between 45 and 60 megabases. At roughly 99 megabases, this tiny litter agaric carries a genome about twice the size of its ecological peers. No source located offers an explanation, which makes genome expansion another open question in a genus full of them.
Tetrapyrgos as an active research frontier
Few genera have moved this much this fast. Nine species were retained in 2015, six Amazonian species were added in 2020, T. chukeatirotei arrived from Yunnan in 2025, and at least eight unnamed lineages already sit in NCBI awaiting description. GenBank holds 782 nucleotide records for the genus and 645 for T. nigripes alone, which is more than enough sequence data to support a population-genetic study that nobody has yet run. Anyone working with a Tetrapyrgos sp. culture is working at the edge of the published record, which is either the attraction or the drawback depending on what they bought it for.
Also available as a culture plate from Out-Grow.
Tetrapyrgos sp. Culture PlateFrequently Asked Questions About Tetrapyrgos sp.
What does "Tetrapyrgos sp." mean on a culture label?
It means the isolate has been placed in the genus Tetrapyrgos but has not been resolved to a species. The abbreviation sp. is standard mycological shorthand for one unidentified species within a named genus. The label is more honest than it looks here, because mean ITS similarity within the genus is around 94.7 percent, at least eight undescribed lineages already sit in NCBI under informal tags, and species boundaries have shifted three times since 2015. On occurrence data alone, a North American isolate is most likely Tetrapyrgos nigripes.
Is Tetrapyrgos the same thing as Marasmiellus nigripes?
Marasmiellus nigripes is an old synonym of Tetrapyrgos nigripes, so a culture sold under either name is the same fungus. GBIF lists seven historical names for the species, including Agaricus nigripes, Marasmius nigripes, Chamaeceras nigripes, Heliomyces nigripes and Pterospora nigripes. Horak published the current combination in 1987. The Marasmiellus name is the one most likely to appear on vendor labels, older field guides and herbarium slips, and both English vernacular names for the species still contain the obsolete genus Marasmius.
Does Tetrapyrgos glow in the dark?
No Tetrapyrgos species has ever been confirmed bioluminescent. Four independent surveys of luminous fungi exclude it. Desjardin and colleagues covered 64 luminescent species in 2008, a 2024 review covered 122, a 2025 review covered 132 across five lineages, and the standing list of bioluminescent fungi includes neither Tetrapyrgos nor Campanella. The rumour most likely spreads by association with luminous marasmioid relatives, and the 2025 review reinforced that point by reassigning two luminous Japanese Marasmiellus species to the Omphalotus lineage.
Is Tetrapyrgos sp. edible?
Treat it as inedible. Japanese reference material rates Tetrapyrgos nigripes as unsuitable for eating, with no mechanism or toxic compound named. No poisoning has ever been recorded for any species in the genus, but no toxicological study has been performed either, so toxicity is untested rather than ruled out. Practically it is also pointless. The caps are around a centimetre across, the flesh is very thin, the stems are tough enough to resist tearing, and the odour and taste are not distinctive.
Can you grow Tetrapyrgos sp. mushrooms?
You can grow the mycelium. You cannot reliably fruit it. No peer-reviewed cultivation protocol exists for any species in the genus, and there is no published substrate formulation, spawn-run duration, fruiting trigger, flush count, yield or biological efficiency figure. What is certain is that the fungus is culturable, because Tetrapyrgos nigripes strain CBS 291.85 is a publicly deposited reference strain that was grown and whole-genome sequenced. The only real-world conditions on record are a vendor's malt extract agar plate held at room temperature.
What family does Tetrapyrgos belong to?
The reference databases disagree. Index Fungorum, Species Fungorum and GBIF place Tetrapyrgos in Marasmiaceae, while NCBI Taxonomy places it in Campanellaceae within the suborder Marasmiineae. Campanellaceae is a validly published family from 2024 and appears in the 2024 fungal outline updates, so this is a genuine disagreement rather than a database error. A 2005 study using nuclear large-subunit data recovered the genus inside the gymnopoid lineage that became Omphalotaceae, which is where the occasional Omphalotaceae claim comes from. Current sequence work does not support it.