[5] Pleopsidium is a genus of crustose lichens, typically forming small, patchy crusts divided into separate, block-like sections (areoles).

The upper surface can be smooth or faintly wrinkled, and is most often a bright, vibrant yellow, though some specimens appear paler and slightly greenish.

The upper cortex—the thin protective "skin"” on top—is made of small, closely packed cells (prosoplectenchymatous), but there is no lower cortex on the underside.

[6] In addition to sexual reproduction through spores, Pleopsidium also reproduces via tiny, flask-shaped structures called pycnidia, which are hidden within the thallus.

Ecologically, these lichens are typically found growing on rocks (saxicolous) in cool and humid environments, where they can often be identified by their distinctive bright yellow crusts.