Acanthotrema has a grey-olive
thallus with a dense, that can occasionally split. The are , taking on angular-rounded to () forms, with a visible and a margin that is lobulate and merged.
Acanthotrema lacks a , and its has a , structure. -tipped are present, as are unbranched with spinulose tips. The of
Acanthotrema range from
septate to and come in shapes ranging from
fusiform to
ellipsoid, with thin septa and rectangular . They are non-
amyloid. This lichen genus does not contain any
secondary chemical compounds. Characteristics that differentiate
Acanthotrema apart from other genera that possess similar fruiting structures are its chroodiscoid apothecia, spinulose periphysoids, and paraphyses. Ascospores in
Acanthotrema have notably thin walls, a characteristic shared only with the genus
Chroodiscus. However,
Chroodiscus does not have periphysoids, possesses paraphyses with smooth apices, and is strictly
foliicolous (leaf dwelling). While certain
Chapsa species, such as
C. astroidea, may bear a resemblance to
Acanthotrema due to the similarity in apothecia and the near-thin-walled, non-amyloid ascospores, these taxa consistently have paraphyses with smooth apices. ==Species==