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Armillaria spp.
I think you mean this study:
Molecular Phylogeny of Northern Hemisphere Species of Armillaria, James B. Anderson and Elida Stasovski. Mycologia, Vol. 84, No. 4 (Jul. - Aug., 1992), pp. 505-516
Common mushroom guides just leave it to level of genus, so I think that should be fine here too.
yes you're right, borealis is more common as the solidipes but they are very similare ( Armillaria borealis is a species of mushroom in the Physalacriaceae family. Phylogenetic analysis of ribosomal DNA has shown that within the genus Armillaria, this species is most closely related to A. solidipes and A. gemina ). And they are look alike. but both borealis/solidipes are to seperate from A. mellea.
i would suggest, armillaria solidipes, because of the somewhat big flakes/spikes, most common in ger. and nl. are the armillaria species: solidipes and mellea.(finnland isn't that different at fungi) when you have seen both 2-3 time, it get easier to seperate them. good luck for the next spotting meik