[1] It is found only in Antarctica, where it forms pale-coloured, circular patches on rock surfaces, typically 1–3 cm (3⁄8–1+3⁄16 in) across, with distinctive finger-like projections that break down into powdery structures.

These circular patches can occasionally grow up to 6 cm (2+3⁄8 in) in diameter, with edges that show neat, fan-like folds and can appear either swollen or slightly flattened.

The species shows particular success on rock surfaces, where it commonly grows alongside other lichens such as Lendemeriella exsecuta, Lepraria neglecta, and Pannaria hookeri.

However, detailed examination of Southern Hemisphere Placopsis material revealed that P. parellina (in the strict sense) is actually a squamulose, non-sorediate species restricted to dry, disturbed habitats in central Chile's coastal ranges, and does not occur in Antarctica or New Zealand.

[2] The species shows morphological similarities to Placopsis fuscidula but can be distinguished by its distinctive laminal dactyls, which are nodular, swollen structures that erode at the tips to form soredia.

These dactyls are easily dislodged by environmental factors such as wind, water, or mechanical abrasion, leaving distinctive pitted holes with eroded, powdery edges.

Placopsis species, including P. antarctica, serve as pioneer colonisers in recently deglaciated Antarctic soils, with molecular evidence showing greater photobiont diversity in specimens from areas that have been ice-free for longer periods.

However, DNA studies have revealed that Antarctic lichen diversity is still incompletely characterised, with new molecular evidence sometimes contradicting earlier phenotypic identifications.

This protected area, covering 1.3 km2 (0.50 sq mi) of ice-free terrain, was established to preserve its diverse biota and geological features as a representative example of maritime Antarctic terrestrial, limnological, and littoral habitats.

Within this protected area, the species occurs at elevations ranging from 65 to 190 m (213 to 623 ft) above sea level, particularly on Chopin Ridge, along Bystry Creek, and on exposed rock outcrops.

[3] Experimental studies using open-top chambers on King George Island have demonstrated that P. antarctica shows significant sensitivity to warming conditions.

Its status as a pioneer coloniser in recently deglaciated areas makes it particularly important for monitoring climate change impacts, though its limited temperature tolerance may affect its role in early soil development and ecosystem succession as warming continues.

[11] The species' vulnerability to future climate change appears particularly pronounced if warming leads to altered precipitation patterns or increased evaporative demand.

This susceptibility is especially significant given P. antarctica's role in colonising newly exposed surfaces following glacial retreat, suggesting potential cascading effects on Antarctic terrestrial ecosystem development.

These protective responses begin to engage when the thallus water content falls below 20%, allowing the lichen to maintain cellular function even under severe desiccation.

The cephalodia maintain photosynthetic capacity at lower water contents than the green algal regions, suggesting a complementary survival strategy that may help the species optimise resource use under varying environmental conditions.

[3] Studies on the Potter Peninsula, King George Island, have demonstrated that P. antarctica is one of the pioneer species that colonises newly deglaciated areas.

Notably, P. antarctica's ability to fix nitrogen through its cyanobacterial partner in cephalodia may play an important role in facilitating subsequent colonisation by other species.