Sixteen species and two varieties of lichenicolous fungi are reported from Rhizoplaca s. lat. Four species and one variety are described as new to science: Caeruleoconidia ahtii Zhurb. (on Rhizoplaca s. str.), with hyaline to pale greyish turquoise, comparatively large conidia; Cercidospora mongolica Zhurb. & Cl. Roux (on Rhizoplaca s. str.), with a reddish brown (above) to pale brownish grey to colourless (below) exciple, mostly 4-spored asci, and (0‒)1(‒2)-septate ascospores, mostly 23‒28.5 μm long; C. tyanshanica Zhurb. & Cl. Roux (on Protoparmeliopsis and Rhizoplaca s. str.), with a uniformly grey exciple, mostly 4-spored asci, and (0‒)1(‒2)-septate ascospores, mostly 25.5‒31.5 μm long; Stigmidium pseudosquamariae Zhurb. (on Protoparmeliopsis), inducing brown cerebriform galls, with consistently immersed ascomata and well-developed pseudoparaphyses of type b sensu Roux & Triebel (1994); and Arthonia clemens var. peltatae Zhurb. (on Protoparmeliopsis), with a brown epihymenium without grey shade. An unidentified species of Leptosphaeria growing on Protoparmeliopsis peltata, and Lichenostigma cf. chlaroterae growing on P. peltata and Rhizoplaca chrysoleuca are briefly characterized. Arthonia clemens is newly reported for Kazakhstan, Kyrgyzstan and the Republic of Sakha (Yakutia) in Russia; Cercidospora melanophthalmae is new to Kazakhstan, Kyrgyzstan and Mongolia; Didymocyrtis rhizoplacae is new to Russia; Lichenoconium lecanorae and Muellerella erratica are new to Kyrgyzstan; Stigmidium squamariae s. lat. is new to Kazakhstan, Kyrgyzstan and Turkmenistan. Didymocyrtis rhizoplacae is documented for the first time on Rhizoplaca subdiscrepans, and Pyrenidium actinellum s. lat. on Protoparmeliopsis. A key to 36 species of lichenicolous fungi and lichens known to occur on Rhizoplaca s. lat. is provided.

Clypeococcum wedinii, a pyrenocarpous ascomycete growing on the lichen genus Bunodophoron in Chile and New Zealand, is described as new to science. It differs from other Clypeococcum species in the combination of the following characteristics: a conspicuous gall formation, scattered, loose to dense stromatic growths sometimes looking like a clypeus, an ascomatal wall composed of both textura intricata and angularis in surface view, a non-amyloid hymenium, an absence of ostiolar filaments, 8-spored asci, and 1-septate ascospores arranged biseriately in the ascus. An updated key to the species of the lichenicolous genus Clypeococcum is provided.

Two species of lichenicolous fungi are described as new to science: Lichenotubeufia etayoi Zhurb. (on Trachyderma), with light orange perithecia up to 360 μm diam., non-fasciculate excipular hairs, and 10–13-septate ascospores, 110–162 × 3–5 μm; and L. tibellii Zhurb. (on Coccocarpia), with light orange perithecia up to 275 μm diam., non-fasciculate excipular hairs, and 5–12-septate ascospores, 50–100 × 3–4.5 μm. An updated key to the species of Lichenotubeufia is provided.

Five species of lichenicolous fungi are described as new to science: Buelliella ohmurae Zhurb. & Diederich (on Icmadophila), with a non-granulose epihymenium, not or only slightly enlarged, pale brown apical cells of paraphysoids and 1-septate, smooth ascospores; Catillaria japonica Zhurb. & Hafellner (on Dibaeis and Pseudobaeomyces), with a medium to dark reddish brown epihymenium, exciple and hypothecium, rather frequently branched and anastomosed paraphyses with only slightly enlarged apical cells without a dark cap, and Catillaria-type asci; Cryptodiscus ihlenii Zhurb. (on Dibaeis), with persistently immersed ascomata, non-amyloid asci and hymenium, not or only slightly enlarged apical cells of paraphyses and narrowly obovate, 1-septate ascospores; Llimoniella chilensis Zhurb. (on Dibaeis and a sterile microsquamulose lichen), with a K+ green exciple and epihymenium and aseptate, broadly ellipsoid ascospores; and Stigmidium phyllobaeidis Zhurb., Etayo & Flakus (on apothecial discs of Phyllobaeis), with a hemiamyloid interascal gel, not previously reported in that genus, well-developed, 1‒2(‒4)-celled periphysoids, elongate asci and hyaline, 1-septate ascospores. An undescribed species of Arthonia (on Pseudobaeomyces) is briefly characterized. Sphaerellothecium coniodes is newly reported for Asia. A key to the 32 species of lichenicolous fungi and lichens known to occur on baeomycetoid lichens and Icmadophila is provided.

Sixteen species of lichenicolous fungi are documented from Siphula-like lichens. Two new genera based on new species are introduced. Amylogalla Suija, Motiej. & Kantvilas, characterized by I+ blue, K/I+ violet vegetative hyphae and ascomatal wall, immersed, cleistohymenial, yellowish to orange ascomata, unitunicate, non-amyloid, 8-spored asci and hyaline, ellipsoid, aseptate ascospores, is described from Parasiphula in Tasmania. Saania Zhurb., characterized by superficial, stromatic, multilocular ascomata, non-amyloid hymenial gel, persistent periphysoids, bitunicate, non-amyloid, 4(–8)-spored asci and narrowly obovate to ellipsoid, 1(–3)-septate, initially hyaline and smooth-walled, later sometimes brown and verruculose ascospores, is described from Siphula in South Africa. Four additional species are described as new: two from Siphula (Cercidospora santessonii Motiej., Zhurb., Suija & Kantvilas and Stigmidium kashiwadanii Zhurb.) and two from Parasiphula (Endococcus hafellnerianus Motiej., Suija & Kantvilas and Pyrenidium macrosporum Motiej., Zhurb., Suija & Kantvilas). Additional hosts and/or expanded geographical ranges are reported for Aabaarnia siphulicola, Epigloea soleiformis, Plectocarpon gayanum and Pyrenidium actinellum. The Southern Hemisphere is the centre of species richness for siphulicolous fungi, with 12 species restricted to this region. Taxa recorded for the Northern Hemisphere are Sphaerellothecium siphulae (arctic and boreal) and the subcosmopolitan Epigloea soleiformis and Pyrenidium actinellum, both of which are also known from various lichen hosts. The distribution of siphulicolous fungi strongly underpins the current generic classification of Siphula-like lichens, with five species being confined exclusively to Parasiphula and nine to Siphula. A key to the taxa occurring on Siphula and Parasiphula is provided.

The lichenicolous fungi Endococcus cladiae Zhurb. & Pino-Bodas, Lichenopeltella soiliae Zhurb. & Pino-Bodas and Lichenosticta hoegnabbae Zhurb. & Pino-Bodas are described as new to science from New Zealand growing on podetia of Cladia species. In addition to their host selection, Endococcus cladiae is distinguished by its ascospore size, (9·9–)11·5–14·1(–15·7) × (2·7–)3·1–3·9(–4·6) μm, Lichenopeltella soiliae by ascomata without ostiolar setae and production of 4-spored asci and 1-septate ascospore, occasionally with three pairs of setulae, and Lichenosticta hoegnabbae by comparatively long, bacilliform to fusiform conidia, (7·8–)9·1–10·9(–12·6) × (1·9–)2·1–2·3(–2·7) μm. Niesslia cladoniicola is reported for the first time from Australasia on C. aggregata in New Zealand. A key to the lichenicolous fungi growing on Cladia is provided.

The new lichenicolous genus Ameroconium (dematiaceous hyphomycetes), with its type species A. cladoniae and the new lichenicolous species Phoma psoromatis (pycnidial coelomycetes), are described, discussed and illustrated. Phoma lobariae is recorded for the first time from the Arctic, Russia and Asia on Lobaria linita.

Cecidiomyces santessonii gen. & sp. nov., found on Stereocaulon species on the subantarctic Macquarie Island (Tasmania, Australia), is described, illustrated and compared with other morphologically similar genera and species. It is characterized by a lichenicolous habit, gall-formation, caespitose to sporodochial colonies, semi-macronematous, monoblastic, determinate conidiophores reduced to conidiogenous cells, solitary, 0–1-euseptate, pigmented conidia, and schizolytic conidial secession.

Twenty species of lichenicolous fungi are reported on Thamnolia species and discussed. Epithamnolia karatyginii gen. et sp. nov., Capronia thamnoliae sp. nov., Cercidospora epithamnolia sp. nov., C. thamnogalloides sp. nov., C. thamnoliae sp. nov., and Sphaerellothecium thamnoliae sp. nov. (var. thamnoliae, var. taimyricum) are described from Thamnolia. Dacampia thamnoliicola and Phoma thamnoliae are introduced ad interim. Cercidospora lecidomae is reduced to synonymy with C. punctillata. Polycoccum vermicularium is new to Asia, Odontotrema santessonii and O. thamnoliae are new to North America, Cladosporium licheniphilum is new to the Arctic, Thamnogalla crombiei is new to Greenland and Svalbard, Stigmidium frigidum is new to Mongolia and confirmed in the USA, Lichenopeltella thamnoliae is new to Bolivia. Cladosporium licheniphilum and Phaeospora arctica are newly documented on Thamnolia and Lichenopeltella thamnoliae on Thamnolia papelillo var. subsolida. Thamnolia vermicularis, supporting 23 species of lichenicolous fungi, is shown to be the 15th most hospitable lichen species in the world. A worldwide key to 23 species of fungi known to occur on Thamnolia is provided.