Cora undulata is a rare species of basidiolichen in the family Hygrophoraceae. It is found in Colombia. Its dark olive-green thalli are foliose, measuring up to 9 cm and comprising 5 to 15 semicircular . This lichen gets its name from the wavy, rippled surface of its lobes and is characterised by whitish to pale orange-brown fertile patches on its underside that form rings mirroring the ridges above. Described as new to science in 2014 from a single location in Casanare Department at 1400 metres elevation, it is currently known only from its type locality where it grows on rocks among mosses in semi-exposed habitats.
The lichen was formally described as a new species in 2014 by Leidy YasmÃÂn Vargas, Bibiana Moncada, and Robert Lücking. The type specimen was collected in Finca El Paraiso (Vereda Centro Sur, Chámeza) at an elevation of . The lichen is only known to occur at the type locality, where it grows on rocks, often associated with bryophytes in semi-exposed microhabitats. The specific epithet undulata refers to the (wavy) surface of the lobes.
Cora undulata grows as a leaf-like (foliose) lichen directly on bare rock or nestled among mosses that coat rock faces. A single thallusâ the integrated body formed by fungal and cyanobacterial partnersâÂÂcan reach about 9 cm in diameter and consists of five to fifteen semicircular lobes. Each lobe is 1âÂÂ3 cm wide and 1âÂÂ2 cm long, often forking once or twice; the seams (sutures) where branches divide are faint or absent. When the lichen is moist the upper surface is a deep olive-green, drying to a whitish grey in herbarium specimens. It is smooth yet marked by fine concentric ridges that give a gently rippled appearance, and its edges are broadly even rather than toothed. The underside is plain white whether wet or dry.
A vertical section through a lobe reveals three main tissue layers with a combined thickness of about 250âÂÂ350 micrometres (üm). The outer (50âÂÂ100 üm) is a protective skin of fungal threads (hyphae) arranged parallel to the surface above and roughly perpendicular below. Beneath this, the (140âÂÂ180 üm) houses the cyanobacterial partner in tight spherical clusters 30âÂÂ40 üm across. Each cyanobacterial cell, 12âÂÂ18 üm in diameter and vivid emerald-green, is wrapped in a sheath of interlocking fungal cells, while additional hyphae 5âÂÂ7 üm thick weave through the layer. The innermost medulla (60âÂÂ100 üm) is a looser mesh of mainly parallel hyphae that provides structural support.
Unlike many lichens, C. undulata bears its fertile tissue (the hymenophore) on the underside. It appears as whitish to pale orange-brown, felt-like patches 1âÂÂ2 mm long and up to 0.4 mm wide, arranged in rings that mirror the ridges on the upper surface. In section these patches are 100âÂÂ150 üm thick and consist of a basal brick-like layer () topped by upright cylindrical hyphae. No mature basidia or spores have yet been observed, and thin-layer chromatography detects no secondary metabolites ( lichen products), so the species is identified chiefly by its distinctive shape, colour changes and underside patches.