Byssoloma spinulosum

Byssoloma spinulosum was first scientifically described by Belgian lichenologist Emmanuël Sérusiaux in 2011. He collected the type specimen in a montane forest in the Owen Stanley Range (Northern Province) at an altitude between 2,100 and 2,400 m (6,900 and 7,900 ft). The species epithet spinulosum—derived from the Latin word for "tiny spines"—alludes to the characteristic pycnidia that appear like small spines along the leaf margins.[2]

This lichen species typically grows along the margins and scars of living leaves, forming irregularly shaped patches that are whitish to pale bluish in colour. When viewed under high magnification, the thallus appears cottony, with a white prothallus sometimes visible between the patches.[2]

The apothecia are rounded and measure 0.3 to 0.6 mm in diameter, with a pale yellowish to whitish margin that is typically byssoid, especially in young apothecia. The disc of the apothecia is initially slightly concave before becoming flat and bluish-black.[2]

A key distinguishing feature of Byssoloma spinulosum is the presence of beaked pycnidia, which are predominantly developed along the margins of leaves. These structures are conical or nearly so, with a short, distinct beak measuring 0.15 to 0.25 mm in height and around 0.2 mm in diameter.[2]

Byssoloma spinulosum is primarily found in the understory of montane rainforests. It has been documented in two localities within the mountains of Papua New Guinea, including the Northern Province and Madang Province. The lichen grows on living leaves, often forming patches that are more than 1 cm (2⁄5 in) in diameter.[2]