The sole species of Crutarndina was first formally described in 1995 by Per Magnus Jørgensen and Irwin Brodo, who originally classified it in the genus Thelotrema.

[3] Sittiporn Parnmen, Robert Lücking, and H. Thorsten Lumbsch circumscribed the genus Crutarndina in 2012 to contain the species after molecular phylogenetics analysis showed that it represented a unique lineage.

[4] The exciple varies in composition, being hyaline (transparent) at the base but becoming carbonised (turning to a black, carbon-rich compound) towards the top.

The ascospores, which are the reproductive spores formed in the asci (spore-producing cells), are fusiform (spindle-shaped) and transversely septate, meaning they have multiple cross walls (septa).

[4] Crutarndina petractoides is predominantly found in oceanic regions, growing on the somewhat shaded, smooth bark of trees, especially Corylus (hazel) and Sorbus (rowan).