Amundsenia austrocontinentalis

The lichen has an areolate growth form, reaching a diameter of up to 3 cm (1.2 in) in diameter; the individual areoles comprising the thallus are 0.2–0.8 mm wide and 0.1–0.3 mm high. The colour of the thallus is deep yellow to pale orange, although abraded or dead specimens can become whitish. The apothecia are either lecanorine to zeorine in form, measuring 0.2–1.5 mm wide, with a flat to slightly concave pale orange disc that often has orange pruina. Ascospores number eight per ascus, and are ellipsoid and polaridiblastic (pierced by a narrow channel) with dimensions of 8–13.5 by 4.0-6.5 μm.^[2]

The species is restricted to continental Antarctica, with confirmed records from the Vestfold Hills, the Windmill Islands and multiple localities in southern Victoria Land, including Ross Island and the McMurdo Dry Valleys. It occurs from the supralittoral zone at 8 m elevation up to roughly 750 m on inland nunataks and valley walls, and can be locally abundant.^[2]

Amundsenia austrocontinentalis is strictly saxicolous, favouring hard siliceous substrates such as granite, dolerite felsenmeer, moraine pebbles or scoria rubble. Thalli are often tucked into narrow fissures or beneath exfoliating flakes where transient melt-water, shelter from katabatic winds and strong insolation create slightly milder microhabitats. It frequently grows alongside other cold desert lichens, for example Austroplaca darbishirei, Lecidea cancriformis and Rhizoplaca melanophthalma. Both the areoles and the apothecia may develop micro-stipes, a trait interpreted as reducing contact with the intensely frozen rock surface in this extreme environment.^[2]