Aspidothelium Vain.
Type : Aspidothelium cinerascens Vain.
Description : Thallus crustose effuse, with partly cartilaginous, cortex-like layer. Photobiont green, chlorococcoid. Ascomata perithecia, sessile, outer wall formed of intricate hyphae, expanded above, disc-like or with wart-like protuberances, colourless; inner wall colourless or sometimes darkened in upper parts, periphyses present. Hamathecium of simple paraphyses. Asci clavate, very thick-walled, 2–8-spored. Ascospores colourless, transversely septate to submuriform, ±fusiform, cells cylindrical or ±cubic. Conidiomata pycnidia, sessile or ±immersed. Conidiophores forming conidia apically. Conidia simple, oblong, colourless.
The genus Aspidothelium is characterised by: perithecioid ascomata, usually with disc-like or verruciform protuberances; clavate, fissitunicate asci, with very thick walls and a small but distinct ocular chamber; simple paraphyses; the occurrence of periphyses; transversely septate or muriform, fusiform to allipsoid ascospores; and a chlorococcoid photobiont (Sérusiaux & Lücking 2001). Species of Aspidothelium are most easily recognised by the pale perithecia not covered by thalline tissue, often with small papillae or teeth in the upper part; the bitunicate asci and the very elegant ascospores (Santesson 1952; Lücking 1992). The genus has foliicolous and corticolous taxa. The genus is placed in the family Aspidotheliaceae, together with Musaespora Aptroot & Sipmaniksson et al. 2004). Eleven species are known, mainly from Central and tropical South America (Santesson 1952; Lücking 1992), Zaire (Sérusiaux 1978), Isla del Coco and Juan Fernandez in the Pacific (Elix & McCarthy 1998), Papua New Guinea (Sérusiaux & Lücking 2001, who also present a key to all known species) and southern South America (Lücking et al. 2003). One species is recorded from New Zealand (Malcolm & Vězda 1995b).
