Cyclothyriella Jaklitsch & Voglmayr, Stud. Mycol. 85: 41 (2016).
Index Fungorum number: IF 817773; Facesoffungi number: FoF 08193, 1 morphological species (Species Fungorum 2022), 5 species with molecular data.
Saprobic on host. Sexual morph: Ascomata and pycnidia clustered in valsoid configuration within KOH-positive tissue in bark, more or less globose, black, peridium pseudoparenchymatous. Brightly colored ostiolar discs present, ostioles periphysate. Hamathecium of apically free paraphyses and narrow branched and anastomosing, trabeculate pseudoparaphyses. Asci cylindrical, bitunicate, fissitunicate but relatively stable in water mounts, with thick endotunica, small ocular chamber, short stipe and furcate base, containing 8 uniseriate to overlapping ascospores. Ascospores ellipsoid, oblong to fusoid, with several thick and dark eusepta, straight or curved, dark brown when mature, verruculose. Asexual morph: pycnidial, morphologically similar to ascomata. Conidiophores absent. Conidia cylindrical, oblong to ellipsoid, 1-celled, hyaline when immature, turning dark brown, smooth, produced on variously shaped phialides (adapted from Jaklitsch and Voglmayr 2016).
Type species: Cyclothyriella rubronotata (Berk. & Broome) Jaklitsch & Voglmayr
Notes: Cyclothyriella is characterised by ascomata clustered in valsoid configuration, cylindrical, bitunicate, fissitunicate asci, and ellipsoid, oblong to fusoid ascospores. The asexual morph of Cyclothyriella is characterised by pycnidia which are morphologically similar to the ascomata, and cylindrical, oblong to ellipsoid, 1-celled conidia. Cyclothyriella rubronotata was described from Ulmus (Ulmaceae) under the name Thyridaria rubronotata however the latter was not congeneric with T. broussonetiae, the type species of Thyridaria. Saccardo (1883) referred the conidial stage of Cyclothyriella as Phoma ulmicola which was wrongly identified as P. ulmigenum by Tulasne and Tulasne (1863). Höhnel (1917) incorrectly combined P. ulmigenum as Melanconiopsis ulmigena (Berk.) Höhn. Petrak (1923) proposed Cyclothyrium for the asexual morphs of Thyridaria and accommodated species such as C. ulmigenum and C. incrustans which has wrongly been placed in Melanconiopsis. Petrak and Sydow (1927) treated Cyclothyrium as a subgenus of Cytoplea which is morphologically similar to Cyclothyrium. Petrak and Sydow (1927) used Cyclothyrium for the asexual morph of Thyridaria rubronotata and proposed that the type species must be C. juglandis based on Naemospora juglandis Schum as the genus is most common on Juglans. This treatment was not followed by other authors as Petrak and Sydow (1927) did not examine the specimen Naemospora juglandis nor Phoma ulmicola and did not consider the chance of host specificity and ignored the fact that Thyridaria rubronotata was found from Ulmus (Chesters 1938; Wehmeyer 1941). Molecular markers available for Cyclothyriella are ITS, LSU, SSU, RPB2 and TEF-1.