And no negativity felt, I appreciate the info, always hard to work with determinations for species I’ve no previous experience with. Back to the drawing board! And soon back to the outcrop, there are several others, with varying degrees of serpentine, and all with very well developed crustose communities. Sure makes you think about growth rates, and what actually happens over decades or centuries, or longer, to the species compositions.

But both Peltula obscurans var. obscurans and var. deserticola are abundant in the Mojave portion of our study area in eastern Nevada. And none of our specimens come anywhere close to this. They should be crustose species, not squamulose. I always think they’re Acarospora in the field! Yes, var. hassei is squamulose, but then as you say, the epihymenium is wrong. And don’t forget your spores are way too big for any of the above.

I wonder if you have a new species. Doesn’t look close to any known species. It approaches some forms of Endocarpon pulvinatum… but not with apothecia!! I’ve seen material like this without perithecia or apothecia… now I wonder if they were the same thing as yours. I wasn’t so lucky and didn’t get fertile material. I’ve been holding my nose and lumping it all into Endocarpon pulvinatum(!)

My observation of “soredia” I believe is a mistake, although there are some scurfy granules on the lobe tips. With that, the trail to this ID is pretty straight forward with the squamulose thallus, large number of spores per ascus, ellipsoid spore shape, and K+R epithecium. I have previously identified_Peltula obscurans var. hassei_ in this region (observation 242820 and _observation 258067). But for some reason it looks like I didn’t do micro on these. Looks like I’ll have to dig those up and finish the analysis. I bet I just went on range, because P. obscurans obscurans is not known north of Los Angeles, a couple hundred miles south of here.

The Lichen Family Heppiaceae in North America. Annals of the Missouri Botanical Garden 57(2): 158-209.

Haven’t committed to this being sorediate, but it seems like it on some lobes. Spores alone don’t fit with anything in the Sonoran Flora, so I’m in a hold pattern until I get some better references.

Ok, so this is presumably a Peltula, but I can’t match it to anything. Updated description below. I’ll get some close ups of the lobes and soredia.

Thalli are discrete, effigurate, about 0.2-1.2 cm, composed of dull dark brown squamules, with imbricate lobes creating a humped form with marginal lobes spread loosely flat on the rock surface. Lobe tips somewhat scalloped, sorediate, with soredia on the underside of the lobe tip as well as the margin. Apothecia rare, immersed, open reddish disk. Pycnidia common, immersed, showing as black punctiform dots. Lower cortex is pale. Rhizines sparse. Hymenium and hypothecium hyaline, epihymenium yellowish-brown, K+R. Hymenial gel K/I+Blue. Asci broadly clavate, tholus K/I+dark blue. Photobiont a blue-green algae.

Spores many per ascus, small, simple, ellipsoid, hyaline. 11.4×3.7, 10.8×4.5, 9.6×4.1, 10.9×4.1, 8.9×3.8. Average 10.3×4.0µm

Except for possible minor disturbance by quick grassland fires, a community like this could be untold eons old. I bet it’s full of all sorts of interesting parasites, too. I love exploring places like this! (Nevada is chock full of them. Let’s hear it for “useless” land! :)