Observation 67102: Agaricus crocodilinus Murrill

growing in grass along treeless roadside, near coastal shrubs.

Species Lists


note giant spores!
short gills, loooooong context.
margin slightly inrolled even at maturity.

Proposed Names

95% (4)
Eye3 Eyes3
Recognized by sight: large firm white cap with stiff peaks like an Amanita magniverrucata, but with free, chocolate brown gills and a short stipe.
Based on microscopic features: giant spores (some up to 15 microns in length!)
Based on chemical features: smelled mushroomy (like portobella), with a very slight hint of almond.
KOH: negative on cap and context.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
By: Jacob Kalichman (Pulk)
2016-09-23 16:09:07 MST (-0700)

Observation pages are for an individual observation of a mushroom – one finding of a species in one place by (usually) one person. Click “Create Observation” in the navigation bar to post your own photos.

By: MushroomNut
2016-09-23 16:05:55 MST (-0700)

Sorry, I didn’t know how to add a photo of the Agaricus crocodilinus I have. :(

Agaricus crocodilinus
By: MushroomNut
2016-09-23 16:04:59 MST (-0700)

I just found this today in central Idaho, just north of Ketchum under a pine tree. At least I believe that’s what it is. I am doing a spore print on a smaller specimen. Could you please ID from the photo. I would like to try eating this, if it’s possible to get a correct ID from my photos.


Amazing specimen!!
By: Charles Seltenright Sr (Shroomin Yooper)
2011-06-13 02:13:08 MST (-0700)
It is growing
By: Alan Rockefeller (Alan Rockefeller)
2011-06-12 19:50:28 MST (-0700)

I gave my friend some gills from this collection and he was able to get the spores to germinate on peroxide agar.

Big is right!
By: Martin Livezey (MLivezey)
2011-05-11 12:25:45 MST (-0700)

So I see there are both big and smaller spores here…, Is this a smash mount or spores collected from a drop? Is this croc. atypical? The top looks mature, but the short gills – are they immature? I would think an Agaricus like this one would be making deep spore prints every three hours…, Christian – maybe you should try these under your ’scope! Thanks Deb, this is almost as good as being there!

By: Christian (Christian Schwarz)
2011-05-10 19:50:53 MST (-0700)
By: Debbie Viess (amanitarita)
2011-05-10 19:38:54 MST (-0700)

A few comments from Rick Kerrigan (with permission):

“I don’t think the species [A. crocodilinus] has been confirmed from any further south than from your locality. Regarding spore size, here are my measurements on 280 spores from 13 specimens:

SPORES dark brown, ellipsoid, (8.6-) 9.2-11.2 (-12.8) × (5.8-) 6.2-7.7 (-8.6) um (longer on bisporic basidia) (N=280, C=13).

“Stresses including slow dessication can result in abnormal (including long) spores in many species.”


micro shots added.
By: Debbie Viess (amanitarita)
2011-05-10 10:28:16 MST (-0700)

still no sporedrop, tho. gill smash mount showed many enormous immature spores, some up to 15 micrometers! in water at 1000×.

note absurdly narrow gill width in comparison to context.

note inrolled cap margin, even at age.

KOH negative.

well Martin…
By: Debbie Viess (amanitarita)
2011-05-10 08:11:17 MST (-0700)

since my report of the average sized spores (“only” up to 11 microns) was underwhelming to some, I am in process of getting a spore drop to see if I can’t find some of those super-gigantic spores. my first slide was a mere smash mount, and no doubt had lots of immature spores.

another curious aspect to this Agaricus is that the gills were extremely short…only a third of the length of the cap context! I’ll post that photo today, too.

still rockin’ the croc…;)

I love the excitement here, but…,
By: Martin Livezey (MLivezey)
2011-05-10 07:07:41 MST (-0700)

Where is the microscopy? The microscopically challenged would love to see these big spores…, How ’bout it Deb? Great find either way!

no yellowing that I noticed…
By: Debbie Viess (amanitarita)
2011-05-09 11:10:17 MST (-0700)

I’ll check again when I section it for the dryer.

any yellow bruising?
By: Britney Ramsey (Riverdweller)
2011-05-09 10:36:02 MST (-0700)

Agaricus crocodilinus ‘var. mutabilis’ Isaacs nom. prov.

Agaricus crocodilinus Murrill var. crocodilinus Mycologia 4: 300. 1912

Which is this?

I wish I lived closer….
By: Tim Sage (NMNR)
2011-05-09 10:27:42 MST (-0700)

So I could go and touch it!

Time to reassess, Tim!

Super Wild!
By: damon brunette (damonbrunette)
2011-05-09 10:23:42 MST (-0700)

Never heard about it or seen such a thing. Rod T. always says about spores varying a lot….. Must say though, that when physically touching mushrooms presents a thrill, one might need to reassess.

What a cool Agaricus!
By: caphillkid
2011-05-09 10:17:48 MST (-0700)
By: Debbie Viess (amanitarita)
2011-05-09 09:48:33 MST (-0700)

“up to 14 microns” is the outer range for giant spores; 8-11 is the norm. this is without a doubt crocodilinus, but I’m sure that Bruns can run the DNA if he so desires.
Come to the May BAMS meeting Erin, and I’ll let you touch it! A little piece of myco-history…;)

By: Erin Page Blanchard (CureCat)
2011-05-09 09:35:46 MST (-0700)

Is “up to 11 µm” really a match for “somewhere around 14 µm”?

spores are a match.
By: Debbie Viess (amanitarita)
2011-05-09 09:01:35 MST (-0700)

up to 11 microns in length.

Check the spores
By: Christian (Christian Schwarz)
2011-05-08 20:33:54 MST (-0700)

They should be huge (for Agaricus) somewhere around 14 µm long.

PS – Totally badass! Nice find.

Created: 2011-05-08 20:20:12 MST (-0700)
Last modified: 2016-09-23 18:22:20 MST (-0700)
Viewed: 1888 times, last viewed: 2018-08-18 06:08:12 MST (-0700)
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