Blue-tinged Cortinarius?

[NickWood]

Bit of a mystery this fungus, so I'm hoping you can help.
Cap: 6cm+, domed, brown top, lighter brown tinged with blue at edge, thinly fibrous, edge inrolled. Darkening to chocolate when wet but not viscid.
Gills: Adnate, close, light brown, darkening with age (because of spores?).
Flesh: Light grey-cream, tinged with blue below surface of cap. No obvious bruising. Had a cold so couldn't smell!
Stem: 75 x 18mm, greyish cream, scales on surface, flesh a little brittle.
Spores: Ochre/rust, 8.5-12 x 5.5-7.5, oval to pip-shaped.
Habitat: Found in loose clusters under oak, in birch/oak woodland.
Maybe it's not a Cortinarius, and the dry cap maybe suggests not.

[NickWood]

To revisit this frustrating fungus, I've added some photos of the early and later stages.
Given the overall features and the web remnants, I'm pretty sure it's a Cortinarius - but here the problems start. According to MushroomExpert.com: "Cortinarius is the largest genus of mushrooms in the world, containing an astounding number of species..." Yikes!
This specimen is hygrophanous, darkening to chestnut/chocolate when wet, and neither the stem nor cap is viscid or glutinous. This seems to narrow it down to the subgenus Telamonia. For the subgenus, this specimen is relatively large, with no umbo and with largish spores. The closest I can find is the Stocking Webcap (C. torvus) but mine is stockingless and the stem somewhat different.
If anyone has any ideas - great - otherwise I'll just have to leave it at that.

[Chris Yeates]

Hi Nick
yes it's a Cortinarius, but there the problems start. The few experts in this group do not agree on a lot of species deliminations and it's now down to sequencing to sort them out and see if there are any constant morphological characters which may help mere mortals in the future. There are (or appear to be) Cortinarius species which can be identified by careful study, but it really is a difficult area.
Chris

[NickWood]

Hi Nick
yes it's a Cortinarius, but there the problems start. The few experts in this group do not agree on a lot of species deliminations and it's now down to sequencing to sort them out and see if there are any constant morphological characters which may help mere mortals in the future. There are (or appear to be) Cortinarius species which can be identified by careful study, but it really is a difficult area.
Chris

Many thanks for your comments, Chris. I’d guess many non-experts like myself naively assume that, armed with camera, microscope and references, every distinctive fungus is identifiable. Clearly not so.

I’ve just come across the article "Cortinarius, subgenus Telamonia, section Disjungendi, cryptic species in North America and Europe" (Liimatainen, et al, 2014) and the authors, who used ITS sequences, add a pertinent conclusion: “This study demonstrates how difficult it can be to identify species only on the basis of morphology, and emphasizes the importance of molecular studies of type and of other specimens, particularly in groups with cryptic taxa.”

Thanks, again, and all the best.

[Logic_AL]

With Birch I would say this is a serious contender for C.anomalus.