Anamorph: conidiomata pycnidia, 80–170 µm diam., black. Peridium 10–40 µm thick, composed of 3–6 layers of irregularly flattened cells. Conidiogenous cells lining the conidiomatal cavity, 6.5–12 x 4–7.5 µm, ellipsoidal to ampulliform, without annellations. Conidia (6.5–) 9–11.5 (–16.5) x (4.5–) 6.5–8.5 (–10) µm, broadly obovoid to subglobose, usually truncate at the base, aseptate, smooth-walled, hyaline or golden brown (pigmentation most intensive in walls), guttulate.
Teleomorph: stromata absent. Ascomata perithecia, (60–)100–220 (–280) µm diam., usually in large clusters and often tightly packed and confluent, subglobose to broadly ellipsoidal, erumpent to ± superficial and then almost sessile, dark brown to black, glossy, tuberculate and often rugose. Ostiole 10–50 µm diam., sometimes forming as an irregular split. Peridium orange-brown or reddish-brown, 20–70 µm thick in exposed parts, 10–35 µm in immersed parts, composed of 4–9 layers of irregularly flattened angular cells 3-12 µm diam., the outer layers pale to dark brown and very thick-walled and the inner layers hyaline. Interascal tissue of persistent septate scarcely branched and anastomosed pseudoparaphyses 1.5–3.5 µm diam., not swollen at the apices, interascal gel I-, K/I-. Asci (66–) 75–90 (–100) x (10–) 12–14 (–15) µm, ± cylindrical to cylindric-clavate, short-stalked, fissitunicate, tholus 0.5–3 mm tall, apical beak often distinct, short, sometimes refractive, cytoplasm becoming intensively yellowish brown to brownish orange with I and K/I, (6–) 8-spored. Ascospores uniseriate or partially biseriate, (11–) 14.5–19 (–24.5) x (4.5–) 5.5–7 (–9) µm, ellipsoidal to narrowly ellipsoidal, the ends rounded, (0–) 1-septate, the upper cell often larger, often constricted at the septum, at first hyaline but finally becoming pale yellowish brown, smooth (sometimes slightly roughened when overmature), without a gelatinous sheath or appendages.
Not formally assessed. Known from four collections made between 2003 and 2014, possibly overlooked though the host lichen is conspicuous and of conservation interest. Perhaps an assessment as Data Deficient would be appropriate.
No sequences are available, and it has been suggested that neither Polycoccum nor Endococcus provide an appropriate generic placement. There is some doubt as to whether GB&I material is conspecific with collections from Alaska (these parasitize Lobaria apothecia, not the thallus as in British collections). The species was originally described from Central America and no recent collections are available from that region.
In GB&I, forming colonies in living thalli of Lobaria pulmonaria.
In GB&I, reported from VC98 Argyll, VC101 Kintyre and VC105 W Ross.