#177: Coprinoid Mushrooms

Coprinoid mushrooms are easy to recognize, at least in theory. Many coprinoid mushrooms have gills that liquefy (“deliquesce”) at maturity, which readily distinguishes them from normal agarics. These fungi produce purple-brown to black spores, so liquefied gills often end up looking like an inky mess. As a result, coprinoid mushrooms are often called “Inky Caps.” Coprinoid mushrooms with gills that do not deliquesce can be identified by their central stipes, dark spores, and relatively thin and fragile flesh.

Description

If classic, toadstool-type mushrooms are like golf umbrellas, then coprinoid mushrooms are like parasols. Coprinoid mushrooms have a central stipe and a pileus that is usually conic to bell-shaped. In some species, the pileus becomes flat in age and maybe even upturned. These mushrooms generally have thin, fragile flesh, but there are a few more substantial species. The gills are either free or attached to the stipe and often liquefy at maturity.¹ If the gills deliquesce, it proceeds from the outside in so that the gills liquefy just as the spores become mature.² Because of the thin flesh and deliquescence, these mushrooms are ephemeral. I find they often disappear completely by noon. Coprinoid mushrooms produce very dark spore prints, which helps distinguish the group from most other mushrooms. The spores range in color from black to purple-brown.¹ The mushrooms may or may not have a partial veil and/or universal veil. Currently, inky caps are divided among four genera: Coprinellus, Coprinopsis, Parasola, and Coprinus.^1,2

Coprinellus and Coprinopsis make up the bulk of the inky caps and most closely match the general description above. The two genera are very similar, so you should use a recent key to accurately differentiate between the two genera.² As far as I can tell (based on information from 2006), Coprinellus does not have a partial veil (and therefore has no ring) and lacks deliquescent gills while Coprinopsis has a partial veil that leaves a ring and has deliquescent gills.¹ Additionally, Coprinopsis species more often produce universal veils that leave warts or patches.³

Parasola includes tiny mushrooms that most closely resemble parasols. The mushrooms have very thin flesh and usually feature deep radial grooves that extend from near the center of the pileus to the cap margin. This arrangement immediately calls to mind an image of a flimsy umbrella. Parasola mushrooms also have gills that deliquesce slowly. Additionally, these mushrooms never produce a universal veil and therefore lack any kind of warts, patches or granules. Unfortunately, this last feature cannot be used by the identifier rule out other coprinoid genera, since the mushrooms may have lost their pileal adornments due to rain or another external factor.^1,2

Coprinus is characterized by large, sturdy inky caps. These mushrooms have thick flesh compared to other coprinoid mushrooms but their gills do liquefy, making it impossible to confuse them with any other group.¹ Coprinus species also have a partial veil that leaves a ring, a cord-like bundle of hyphae that runs up the center of the stipe, and gills that often start pinkish before turning black.² Many Coprinus mushrooms, such as the well-known C. comatus, feature scaly caps that are nearly cylindrical before they begin to open.¹

The genera Psathyrella and Panaeolus are sometimes included in the coprinoid mushrooms. I decided to include them here because they are closely related to the main group of coprinoid mushrooms⁴ and because they generally have darker spore prints than the strophariaceae.¹ None of the mushrooms in Psathyrella or Panaeolus have deliquescent gills, so they’re usually not called “Inky Caps.”

Psathyrella mushrooms have a thicker pileus than most coprinoid mushrooms, but their stipes are distinctly flimsy. This genus is known for producing mushrooms with stipes that snap in half cleanly and easily. These mushrooms are small to medium in size, are brown to gray in color, have a conic to bell-shaped to convex pileus, have gills that are attached to the stipe, and produce black to purple-gray to brown spores. Many Psathyrella species are hygrophanous, meaning they change colors as they dry out.^1,4,5

Panaeolus consists mainly of “Little Brown Mushrooms” (LBMs). These mushrooms are small, are grayish or brownish, have thin flesh, have conic or bell-shaped pilei, produce a purple-brown to black spore print, and have gills that are mottled with various shades of black.^1,6 Their small size means that they display relatively few features and are not particularly interesting.

Coprinoid mushrooms are all saprobic and spend their time decaying various plant and animal matter. Inky caps grow on a variety of substrates, including: dung, grass, wood, and leaf litter.^1,2 Psathyrella species generally grow on various types of plant debris, although the group includes at least one mycotroph.^1,5 Panaeolus is commonly found on horse and cow dung but may also appear on other animal feces, in grassy areas, and on leaf litter.^1,6,7

Identifying Coprinoid Mushrooms to Species

Most coprinoid mushrooms are difficult to identify down to species. There are a few species in each genus that are easy to pick out. Most people learn a few edible species and ignore the rest. Beyond that, things get complicated very quickly. One problem you’ll encounter is that morphological features quickly disappear in deliquescent species. Even if you have a good specimen, you may be stymied by the heavy reliance on microscopic examination or by the lack of good keys to species in your region. If you’re determined to try and identify your (not distinctive) mushroom down to species, be prepared for a lot of work. Before you get in too far, try the keys linked at the bottom of this page. For delving into the inky caps, try this site, which uses names that are now out of date. For an in-depth study of Psathyrella, check out The North American Species of Psathyrella by Alexander Smith (available online here).

Similar Species

Black-spored coprinoid mushrooms without deliquescent gills are difficult to confuse with any other group of mushroom. The closest match would be the Gomphidiaceae (FFF#178), which have gray to black spore prints but feature thick flesh and decurrent gills. Coprinoid mushrooms are much more dainty and have free or attached gills.¹

Coprinoid mushrooms that produce lighter spores and do not deliquesce are more difficult to separate from other mushroom groups. The spore print color could also be found in Agaricus (FFF#174) or the stropharioid mushrooms (FFF#185). However, Agaricus produces stocky mushrooms with thick flesh, which means you are unlikely to confuse them with the dainty inky caps. Unfortunately, there is more morphological variety among stropharioid mushrooms. Most stropharioid mushrooms have thicker flesh than inky caps, but both groups include LBMs. Panaeolus can often be separated from other LBMs thanks to its mottled gills. Most Psathyrella species can be distinguished by stipes, which easily snap in half. If your LBM doesn’t key out with the coprinoid mushrooms, try looking at stropharioid mushrooms.^1,8 LBMs are not very well treated in field guides because they are notoriously difficult to separate from one another. If you really want to identify your LBM, you’ll need a good key and a microscope.

Edibility

Coprinoid mushrooms include edible species as well as poisonous species with a wide variety of toxins. The three most commonly eaten coprinoid mushrooms are probably Coprinus comatus, Coprinopsis atramentaria, and Coprinellus micaceus. Of these, C. comatus is the most sought-after. Obviously, you should collect only young specimens for the table. Liquefied coprinoid mushrooms do not make a pleasant meal. Some coprinoid species, such as the “edible” C. atramentaria, contain the toxin coprine (FFF#095) and can make you sick if you drink alcohol with your mushrooms. Panaeolus includes some species that produce the hallucinogenic compounds psilocybin and psilocin (FFF#098). Apparently, some people eat those for their hallucinogenic properties. However, given that most Panaeolus species are LBMS, I think most people would consider them too small to bother with.^1,7

Taxonomy

Thanks to DNA sequencing, the inky caps recently went through a few taxonomic changes. Up until the 1990’s, all inky caps were placed in the genus Coprinus. In 1994, mycologists sequencing mushroom DNA discovered that the DNA of C. comatus was very different than that of most other inky caps. Amid mounting evidence to support that finding, the genus was split into four genera in 2001. Coprinellus, Coprinopsis, and Parasola contained the bulk of the inky caps and were assigned to the family Psathyrellaceae. Coprinus ended up with a mere handful of species and was assigned to the family Agaricaceae. This makes Coprinus more closely related to Agaricus (FFF#174) and the lepiotoid mushrooms (FFF#173) than to any other inky caps. The other genera are more closely related to Panaeolus and Psathyrella, which I described above. Since the inky caps belong to two different lineages, deliquescent gills must have evolved at least twice, providing yet another great example of convergent evolution.^2,3

So why did Coprinus end up with just a few inky caps? Since it was the original inky cap genus, shouldn’t it have gotten most of them? The reason Coprinus ended up so small is that its type species was C. comatus. When taxonomists create a new genus, they have to assign that genus a “type species,” or a particular species they think is most typical of that genus. This is useful because it tells future taxonomists, “genus X should include all the species that are similar to species Y.” Long before 2001, mycologists decided that C. comatus was the quintessential Coprinus. So, when it came time to split up the genus, the mycologists had to remove all the mushrooms that were unlike C. comatus. Unfortunately, that included the majority of the species in Coprinus. In 2007, some mycologists proposed changing the type species of Coprinus to C. atramentarius,* which would have kept the name Coprinus with the largest genus of inky caps. This change was not made and we ended up with the four genera as they are today.³

Genetic studies of coprinoid mushrooms are ongoing, so many of the mushrooms in these genera are likely to get shuffled around in the future. The most important mushrooms, such as the popular edibles, are probably the most thoroughly studied and will probably keep their names. More complete genetic studies may also result in new genera. Psathyrella is currently a very large genus, which means mycologists will probably split it up. For example, some Psathyrella mushrooms will probably get moved into the genus Lacrymaria.^2,5

Kingdom	Fungi	Fungi
Division	Basidiomycota	Basidiomycota
Subdivision	Agaricomycotina	Agaricomycotina
Class	Agaricomycetes	Agaricomycetes
Subclass	Agaricomycetidae	Agaricomycetidae
Order	Agaricales	Agaricales
Family	Agaricaceae	Psathyrellaceae
Genus	Coprinus Pers.9	Coprinellus P. Karst.10 Coprinopsis P. Karst.11 Panaeolus (Fr.) Quél.12 Parasola Redhead, Vilgalys & Hopple13 Psathyrella Fr. ex Quél.14

* I referred to C. atramentarius earlier, but then I called it C. atramentaria. Why did the name change slightly? Down here, I am talking about the mushroom being considered part of the genus Coprinus. Based on the rules of Latin, that genus name is male and the specific epithet must also be male: Coprinus atramentarius. Today, the mushroom belongs to the genus Coprinopsis, which is female. When that change happened, mycologists had to change the ending of the specific epithet to match the gender of its new genus: Coprinopsis atramentaria.