Leptogium burnetiae C.W. Dodge

Image location: Kalatope wildlife Sanctuary, Dalhousie, Himachal Pradesh, India

There are a few possibilities. Several species of Leptogium are characterized by dense white “tomentum” underneath, just like this — L. saturninum and L. burnetiae are common and widespread, for example. Coccocarpia palmicola can also have white “tomentum” sometimes (undescribed species?). But that species is much smaller and the lobes are (in my experience) much more appressed than this. It’s hard to get an idea of scale from your photos, but I’d lean toward Leptogium. I see L. burnetiae is on the Bhutan checklist, but not L. saturninum. (Of course, there are one or two other species on the list I don’t know, as well.)

[Oh, and all the species mentioned can and frequently do grow on both rock and trees — no help there.]

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