Thalli of
Rhizoplaca parilis usually form tightly attached,
rosettes that can be mistaken for
R. melanophthalma: they have radiating lobes with slightly up-turned tips, an upper surface suffused with yellow-green
usnic acid, and a dark, often glossy when
apothecia (fruiting bodies) are present. Minute features such as lobe width, marginal (scalloping) or provide no reliable separation from lookalike taxa. Instead, identification rests on a combined assessment of chemistry and
DNA sequence data.
Thin-layer chromatography typically reveals usnic and
psoromic acids as major constituents, accompanied by
constipatic,
dehydroconstipatic and
dehydroprotocetraric acids. Many thalli also contain
lecanoric and
orsellinic acids in significant quantities, while
gyrophoric acid and several
O-demethylated
derivatives appear sporadically. No single metabolite profile is diagnostic, but the suite involving orsellinic-series compounds is otherwise unknown in the complex. Superficially the lichen presents as a compact crust; however, rare collections possess slightly looser margins that suggest an incipient tendency toward a vagrant life-form. The is a
green alga of the genus
Trebouxia. Microscopic examination shows one-celled
ascospores typical of the genus, but these fall within the range of dimensions reported for allied species and therefore offer little taxonomic utility. ==Habitat and distribution==