Megalospora galapagoensis has a
thallus with a yellowish grey to whitish grey colouration, with a glossy and thick texture. It displays an uneven to slightly surface, expanding up to 20 cm in diameter. The species is characterised by the presence of
soredia, which initially appear as coarse, corticated before merging into confluent and (spotted) formations. The species'
apothecia are round, measuring 0.5–1.5 mm in diameter and reaching up to 0.6 mm in height. The apothecial start as concave in young specimens, flattening or becoming slightly convex as they mature. These discs are grey-black to black, glossy, and lack any . The margins of the apothecia are prominent and thick, with a black colouration. The is brownish, with the having a reddish-brown colour and a thickness of 10–20
μm. The brown stands at a height of 100–130 μm. The
hymenium of the species reaches a height of 200–250 μm, is
hyaline (translucent), strongly , and has an
amyloid reaction. As for the , they are singular, hyaline, contain from 3 to 5
septa (internal partitions), and measure 45–75 by 15–25 μm. The secondary chemistry of
Megalospora galapagoensis includes
usnic acid and
zeorin. ==Habitat and distribution==