Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: foliose to subfruticose, usually forming small tufts of ascending lobes, up to 7 cm across, irregularly lobate lobes: linear spathulate or paddle-shaped, rarely branched, suberect, partially imbricate, up to 5 mm wide, convex, ciliate; cilia: prominent, usually simple, marginal whitish, up to 4 mm long upper surface: white to grayish white, mostly with cilia if not densely covered by pycnidia; soredia and isidia absent upper cortex: prosoplectenchymatous medulla: white lower cortex: absent lower surface: white or variegated ochraceous, apically sorediose, erhizinate Apothecia: common in epitype, terminal to subterminal, substipitate, 1-5 (-10) mm diam., lobulate, ciliate, situated at the end of the ascending lobes; disc: dark brown, densely pruinose asci: cylindrical to subclavate, 8-spored ascospores: brown, l-septate, narrowly ellipsoid to fusiform, Pachysporaria-type, without sporoblastidia, 31-34 x 13-15.5 µm Spot tests: cortex K+ yellow C-, KC-, P+ yellow; medulla K+ yellow, C-, KC-, P- Secondary metabolites: cortex with atranorin and chloroatranorin; medulla with atranorin, zeorin and an unknown ochraceous pigment. Substrate and ecology: growing on tree trunks and branches in fairly open but moist situations World distribution: known from Central and South America, Africa and Asia Sonoran distribution: not known from the Sonoran Desert region, but present in other parts of Mexico and might eventually be found in the Sonoran Desert area. Notes: Heterodermia comosa is recognized by its helmet-shaped lobes with cilia both on the margins and upper surface and the absence of soralia. Apothecia and pycnidia were not seen in Mexican material.