Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, up to 2 (rarely 3) cm in diam., +orbicular lobes: rounded-crenate to slightly elongate, 1-3 mm broad, flat to weakly pitted, sometimes weakly canaliculate, prostrate or weakly ascending upper surface: tan-brown to brown or occasionally dark brown, epruinose, dull or weakly shiny, frequently becoming papillate in mature areas; papillae and the lobe edges: +conspicuously whitish pseudocyphellae, without soredia or isidia upper cortex: paraplectenchymatous medulla: white lower cortex: paraplectenchymatous lower surface: almost white or pale tan to pale brown, +smooth to weakly trabeculate or rugose, dull or weakly shiny near the periphery (rarely with a patchy white pruina); rhizines: sparse but usually +scattered across the lower surface Apothecia: frequent and often becoming numerous, up to 3.5 mm in diam., +concave or irregularly convex with age, margin becoming crenate-papillate, bearing pseudocyphellae on the papillae ascospores: ovoid to more usually ellipsoid, 6-8 x 4-5 µm Pycnidia: black, weakly emergent, submarginal and often laminal conidia: bifusiform, 5-6.5 x 1 µm Spot tests: cortex and medulla all spot tests negative (medulla sometimes reacts CK+ pale yellow, slowly) Secondary metabolites: 2-3 lichesterinic acid type fatty acids (high Rf). Substrate and ecology: bark or wood, often on twigs World distribution: western North America from central Mexico northwards to Canada Sonoran distribution: eastern Arizona and Chihuahua. Notes: Before the apothecia become numerous and crowded, Tuckermanella arizonica might be mistaken for a small specimen of Tuckermannopsis orbata. It differs from that species by its smaller, more prostrate, loosely appressed or weakly ascendant thallus with sparse rhizines usually all the way to the lobe ends. Also, the marginal whitish pseudocyphellae on lobe edges of T. arizonica are missing in T. orbata. Tuckermanella arizonica commonly grows on twigs, where it is often smaller and more compact, bearing numerous crowded apothecia, and thus having a superficial resemblance to Tuckermannopsis sepincola, a northern species which has not been found in the Sonoran region. Tuckermannopsis sepincola has ascendant lobes, even when young, and the lobe margin and thallus upper surface remain rather smooth (not or weakly crenate, without papillae). Also, in T. sepincola, the pycnidia are +directly on the lobe margins, distinctly emergent and sometimes taller than they are broad (only c. 50 µm broad). In T. arizonica, the pycnidia may be largely concentrated on or near the lobe margins, but laminal pycnidia are also common on occasional lobes or thallus regions. These pycnidia are black but are only weakly emergent (and often two to three times as broad as they are tall), unlike the distinctly emergent pycnidia of the Tuckermannopsis species. Several unusually prostrate specimens had narrower, flatter lobes than the typical specimens, and resembled Tuckermanella weberi, which can be distinguished by positive spot tests in the medulla and less conspicuous marginal pseudocyphellae.