On the road to the Upton State Forest

Today we came across an impressive mushroom with rusty brown spores and caps up to 18 inches across. This looks like a Gymnopilus, but which one? According to the description on MushroomExpert.com, this could be G. ventricosus, but that is supposedly restricted to the west coast. MushroomObserver has lots of records of G. ventricosus, but they are mostly from California, Oregon and Washington, with one observation from Arizona (scroll down for GBIF and MycoPortal records, which include one observation in Colorado).

It’s been a crazy weather year, with a long drought in the summer and lots of rain recently. Subjectively, it seems that a lot of the mushrooms that have come up recently are larger than usual (particularly ectomycorrhizal taxa). Perhaps this is just a big specimen of the widely distributed G. junonius?

Anyone with ideas is invited to send e-mail. This was in the front yard of a house with a prominent “no trespassing” sign, so we did not collect the fruiting body (but now we know where it lives). Click images for full-size versions.

Update: I went back to (discreetly) collect a piece of the mushroom, and Alfredo Justo checked the spores, which are 8-10 x 4.5-6.5 um. This fits pretty well with G. junonius, but it is out of the range for G. ventricosus (7.5-9 x 4-5.5 um). So, this is probably G. junonius. Too bad. I was hoping for a dramatic range extension, but it is still a cool find.




Here are the distribution maps from GBIF for G. ventricosus (left) and G. junonius (right):


Here is the Colorado collection from the MycoPortal, with a link to the specimen record and a nice image: