The loosely attached grey, whitish, or brownish-grey
thallus of
Pyxine profallax reaches a diameter of up to . A mat of shiny black
rhizines attach the thallus to its bark . The making up the thallus are up to about 1 mm wide, and divide more or less . They have
pseudocyphellae on the margins and a upper surface texture. Neither
soredia nor
isidia occur in this lichen, but it does have
ascomata of the
obscurens-type, measuring 0.5–1 mm in diameter, with black . The , which number eight per
ascus, have a single
septum and measure 16–20 by 6.5–8
μm.
Pyxine profallax contains
norstictic acid as a major compound,
testacein (submajor), and
atranorin as a minor
secondary metabolite.
Thin-layer chromatography shows that it also contains the same chemical array of
terpenes that are found in its namesake,
P. fallax. ==Habitat and distribution==