Thallus: foliose, up to 5 cm in diam., +orbicular lobes: elongate and more or less irregularly crenate-laciniate, 0.5-1.5(-2) mm broad, flat to weakly concave, prostrate upper surface: tan-green to olive-green, olive-brown to brown centrally, epruinose, rather shiny at the periphery and dull inward, the lobe edges with inconspicuous whitish pseudocyphellae, without soredia or isidia upper cortex: paraplectenchymatous medulla: white lower cortex: paraplectenchymatous lower surface: almost white to pale tan, smooth to weakly rugose, +dull; rhizines: sparse, simple, more or less concolorous with the lower surface or darkening Apothecia: numerous, up to 3.5(-4.5) mm in diam.; margin: becoming crenate-papillate (with pseudocyphellae) ascospores: ellipsoid, 7-9 x 4-5 µm Pycnidia: black, weakly to moderately emergent (but definitely broader than they are tall), mostly marginal or submarginal but some also laminal conidia: not seen Spot tests: cortex and medulla all spot tests negative Secondary metabolites: caperatic acid. Substrate and ecology: pine bark World distribution: southern Mexico Sonoran distribution: not yet known for the Sonoran area. Notes: Although Tuckermanella fendleri is generally a much smaller species, the largest specimens (from e.g. northern Mexico) do overlap in size with T. subfendleri. The two can be distinguished with certainty using chemistry, but are not known to be sympatric. Another species with caperatic acid is T. pseudoweberi, but that species has a distinctly brown coloration and more conspicuous marginal pseudocyphellae. Most of the thalli in T. pseudoweberi also have a distinctive pale yellow to ochre yellow pigment (K+ violet) in part or all of the medulla.