Bolbitius titubans

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Given the gill colour, I wonder if this is a species of Bolbitius - or something else in the Bolbitiaceae.

@Heino1 hmm, that is a possibility. The shape is unlike any Bolbitius I've seen, did you have a species in mind? You're right, the gill colour is not right for this family - I'll rescind my confirmation.

All that I can suggest is an aged Bolbitius titubans. A search for that species turned up a number of photos (on mycologically reliable websites) that have similarities with this sighting. On his MushroomExpert website Michael Kuo makes this interesting observation: Robust specimens are found on dung and in heavily fertilized soil, while flimsy specimens can be found in grassy areas with less nitrogen. He also refers to a 2015 molecular study of Bolbitius in Russia which found four groups within Bolbitius titubans. A little while ago I read the discussion parts of that paper and here are some of the authors’ observations:

(Group 1) Brightly coloured and fragile basidiocarps with a distinct yellow tint in combination with large, thick-walled basidiospores.

(Group 2) Faded basidiocarps with whitish, pale yellowish or beige pileus, without bright yellow tones, and white or pale lemon-yellow stipe.

(Group 3) Characterised by muted colouration of basidiocarps, not containing vivid yellow tones, but having greyish yellow, yolk-yellow, or olive-yellow pileus, wrinkled or venous at center. Thue authors found no clear taxonomic criterion, apart from pileus colouration, to separate this collection from the other groups.

(Group 4) There is no convincing morphological evidence of its independent status within the whole B. titubans complex other than significantly smaller basidiospores, with dimensions not overlapping those in other studied collections.

The authors refrained from equating the four groups to four distinct species, saying that their study was not sufficient to justify such a step. Naturally there is the question of what a comparable study across a broader geographical area would show. Today I have read more about Bolbitius titubans than the sum of all that I had previously read about this species!

@Heino1 wowza! As always, fantastic information! So, shall we label this as a Bolbitius?

Yeah, I'll go with titubans (and have also done so with Bolbitius titubans (Yellow Fieldcap Mushroom)).