Defining features of this lichen include the unique crescent-shaped structure of its hyphophores (spore-producing organs), the single-spored asci, and the relatively small size of the ascospores.

The lichen species Gyalideopsis aptrootii was formally described and classified by Amanda Barreto Xavier-Leite, Marcela Cáceres, and Robert Lücking in 2018.

[2] The type specimen was discovered by Cáceres and Aptroot in the Parque Estadual do Acaraí [pt], located in São Francisco do Sul, Santa Catarina, Brazil.

The white to pale grey crustose thallus lacks clusters of calcium oxalate crystals and has a cartilaginous, corticiform layer, giving it an uneven appearance.

[2] At the time of its original publication, Gyalideopsis aptrootii had only been identified in a preserved coastal forest habitat in the extratropical portion of southern Brazil.