Gyalideopsis ellipsoidea is a crustose lichen, meaning it grows as a thin crust closely adhering to its substrate. It features a shiny grey thallus that is very thin and follows the contours of the bark surface. The thallus is surrounded by a narrow black prothallus line (a border-like structure). The reproductive structures (ascomata) are superficial, appearing on the surface rather than embedded in the thallus. These structures range from round to elongated, measuring 0.2–0.4 mm wide and 0.2–0.6 mm long. They have a concave dark grey disc that is not pruinose (lacking a powdery coating). The margin around the disc is raised, sometimes curving inward, and pale grey, approximately 0.1 mm wide.[2]
Under microscopic examination, G. ellipsoidea has distinctive features including:[2]
- A black hypothecium (the tissue beneath the spore-producing layer) that extends between the hamathecium (sterile tissue among the asci) and the excipulum (outer protective layer)
- Lax paraphyses (sterile filaments) that are mostly unbranched with gnarled, brown tips
- Cylindrical-clavate asci (spore-producing cells) containing eight ascospores each
- Hyaline (colorless), broadly fusiform to somewhat clavate ascospores with 3 septa, measuring 11–13 by 5.5–6.5 μm
The species does not produce any secondary metabolites detectable by standard chemical tests or thin-layer chromatography.[2]
It differs from similar species like Gyalideopsis philippiae by its dark grey disc, black hypothecium, and ascospores with three septa. While many Gyalideopsis species have richly anastomosing (interconnecting) paraphyses, G. ellipsoidea has mostly unbranched paraphyses, which appear to correlate with its numerous asci.[2]
