Sicut Crustospathula macrocarpa Aptroot & Schumm, sed ascosporis minoribus, stipitibus sorediigeris brevioribus et materia chemica differt.

Type:— THAILAND. Nakhon Ratchasima Province: Pak Chong District; Khao Yai National Park, at km 33, in a pristine ‘ Dry Evergreen Forest’, ± 810 m, 14°27’48’’ N, 101°22’14’’ E, 12 March 2011, K. Kalb & K. Buaruang (holotype RAMK, isotype hb. Kalb 38798).

Etymology:—The new lichen is named after the National Park where the type was collected.

Thallus scurfy, green, grey-green to grey, consisting of agglutinating globular to flattened patches 25–50 µm wide, growing on a webby, white hypothallus, very similar to those present in many species of Malmidea. Soralia numerous, whitish, with a greenish tinge in part, with many tiny crystals, globose, 15–25 µm wide, originating from the tips of stalks. Stalks cartilaginous, beige to off-white, unbranched, cup-shaped, 80–110 µ m high and 200–300 µ m wide. Apothecia numerous, ± round, 0.6–1.2 mm diam., solitary, sessile to appressed, medium brown to dark brown, margin paler, dull, not raised above the disc, 0.1 mm wide; disc flat to strongly convex with age, not pruinose. Excipulum hyaline, without algae, with many tiny crystals that are also present under most of the apothecium. Hymenium clear, 50–75 µm high, yellow but tinted orange in lower part. Hypothecium orange brown, 20–30 µm high. Asci 8-spored, Bacidia - type. Ascospores hyaline, rod-shaped to small-ellipsoid, straight, distinctly 1-septate, 11–16 × 2–3 µm. Pycnidia not seen. Chemistry: an unknown substance with ± the same R f -values in solvents A, B’ and C (Elix & Ernst-Russell 1993) as atranorin, but showing an ice-blue fluorescens in UV before and after charring. Atranorin, lobaric acid and 2’- O -methylperlatolic acid could not be detected by means of TLC.

Notes:— Crustospathula was initially described as a monotypic genus (type species: C. cartilaginea Aptroot) to accomodate an enigmatic lichen from Papua New Guinea (Aptroot 1998) with peculiar stalked, cartilaginous soralia. Aptroot & Schumm (2009) subsequently described two further species, namely C. macrocarpa Aptroot & Schumm from the Philippines and Crustospathula sp. from French Guiana. Kalb (2011) described an additional species, C. humboldtii Kalb from Venezuela, which differed from the closely related C. macrocarpa by the presence of atranorin and from C. cartilaginea by the absence of 2’- O - methylperlatolic acid. Crustospathula khaoyaiana is closely related to C. macrocarpa, but differs in having shorter stalked soralia (80–110 µm versus 0.7 mm high), shorter ascospores (11–16 µm versus 17–22(–25) µm long) and alternative chemistry. Lobaric acid is present in C. macrocarpa, but is absent in C. khaoyaiana which contains an unknown substance.