Menegazzia fortuita

The lichen forms an irregular rosette or spreading patch up to about 3 cm across. It is foliose, meaning the thallus resembles tiny, leafy lobes rather than a crust. Those lobes are hollow, extremely fragile and measure 0.5–1.5 mm wide, branching in a rather untidy, forked fashion. Their upper surface ranges from off-white through grey-brown to almost black, often becoming glossy with age, and lacks any powdery soredia or finger-like isidia. Scattered oval to round perforations (0.1–0.6 mm) pierce the surface; their rims show flecks of the white inner tissue (medulla). Because the species is saxicolous (rock-dwelling), the entire thallus lies close against or slightly lifted from its substrate.^[1]

Rounded fruit-bodies (apothecia) are frequent. They sit flush with, or a little above, the lobe surface and mature into discs up to about 0.7 mm across, with a dull brown-black interior ringed by a similar-coloured margin. Microscopic examination shows clavate asci that hold just two colourless, ellipsoid spores – each longer than 60 micrometres (μm) and often packed with tiny oil droplets. Chemical spot tests yield cortex K+ (yellow) and medulla K+ (yellow), confirming atranorin in the outer layer and a stictic acid complex in the medulla; reactions with C and KC are negative. Immersed flask-shaped pycnidia produce slender, rod-shaped conidia (4.5–7.5 × 0.7–1 μm) that provide a second means of asexual dispersal.^[1]

Menegazzia fortuita is known to occur only in four sandstone outcrops in Morton National Park, south-eastern New South Wales. It grows on Hawkesbury sandstone blocks and ledges within open Eucalyptus woodland, conditions that provide intermittent shade, regular moisture from run-off, and a generally nutrient-poor, siliceous substrate. Associated lichens include rock-dwelling species of Buellia, Lecanora, Pertusaria, Ramboldia and Xanthoparmelia, indicating a community adapted to the exposed but not fully coastal sandstone environments of the Southern Tablelands. All collections lie within a relatively small area of the park, suggesting the species may be a local endemic.^[1]