Acanthotrema is a genus of lichens in the family Graphidaceae. The genus was circumscribed by German lichenologist Andreas Frisch in 2006, with Acanthotrema brasilianum assigned as the type species. Acanthotrema species are commonly found in rainforests ranging from lowland to montane environments.

Description
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

Species Fungorum accepts six species of Acanthotrema:
Acanthotrema alboisidiatum 
Acanthotrema bicellulare 
Acanthotrema brasilianum 
Acanthotrema frischii 
Acanthotrema kalbii 
Acanthotrema minus  – Brazil

References

Graphidaceae
Lichen genera
Lecanoromycetes genera
Taxa described in 2006