Erioderma borbonicum is a little-known species of corticolous (bark-dwelling), foliose lichen in the family Pannariaceae.

The lichen forms a dense, cushion-like thallus with a diameter of 3 to 4 cm, with flat, slightly overlapping lobes with a grey-brown upper surface and cream-coloured underside.

The collection site was about 3.5 km (2.2 mi) southwest towards Caverne Mussard, at an elevation of 1,980 m (6,500 ft) above sea level.

The inner layer, known as the medulla, is densely packed with vertical chains of Scytonema, a type of cyanobacteria, with individual cells roughly 10 μm in diameter.

The supporting structure beneath the spore-producing layer (hymenium), called the subhymenium, is brown and consists of densely interwoven hyphae measuring 60 to 80 μm wide.

Additionally, marginal pycnidia (conidia-producing structures) are present, appearing as brownish-black, wart-like formations up to 200 μm in diameter.