This is a key to a very heterogeneous group of species which are superficially similar in having biatorine apothecia, polysporous asci and simple ascospores. The following genera are included:
1) Biatorella De Not. - This genus, which is included in the Biatorellaceae within the Lecanorales, comprises c. 30 species. Other species formerly included in Biatorella have been transferred to Sarcosagium (having smaller, marginate apothecia with a well-developed true exciple), Biatoridium (asci with a multilayered K/I+ blue outer apical dome), Sarea and Tromera (non-lichenised resinicolous fungi). Biatorella was poorly collected in Italy, both for the rarity of the species, and because they are easily overlooked.
2) Biatoridium Körb. - A small genus that was resurrected to accommodate 3 species differing from Biatorella and Strangospora in the clearly multilayered asci with a K/I+ blue apical dome (Hafellner 1994). Its taxonomic position within the Lecanoromycetes is still unclear.
3) Piccolia A. Massal. - A small genus of crustose lichens with only 7 species, characterised by the presence of anthraquinone pigments in the apothecia. Its taxonomic position within the Lecanoromycetes is still unclear. For further details on the only species occurring in Italy see Hafellner (2004).
4) Sarcosagium A. Massal. - A monotypic genus including an inconspicuous, ephemeral species appearing in autumn on soil and decaying mosses in disturbed sites, including urban wastelands and mine spoil heaps. The genus is currently classified in the Thelocarpaceae, but its precise phylogenetic placement within Pezizomycotina still remains unknown (Miadlikowska & al. 2014).
5-6) Sarea Fr. and Zythia Fr. – These two genera were formerly treated under Sarea, and include resinicolous, non-lichenised fungi that have been often treated by lichenologists due to superficial similarities with the genus Biatorella. In early studies, Sarea was placed in the Acarosporaceae, based on the polysporous asci and the thickened ascus apex (Poelt 1974). Because the genus closely resembled Agyrium Fr., Hawksworth and Sherwood (1981) proposed its placement within Agyriaceae. Ultrastructural observation of the ascus apex by Bellemére (1994) placed the genus in an uncertain position within Lecanorales. In their phylogenetic molecular study, Reeb & al. (2004) showed that Sarea did not group with Lecanoromycetes and treated the genus as Pezizomycotina incertae sedis. Subsequently, Hodkinson & Lendemer (2011) provisionally placed Sarea in Trapeliaceae based on morphology, as they believed that the sequences generated by Reeb & al. (2004) could potentially have been contaminated. Miadlikowska & al. (2014) confirmed the placement of Sarea outside Lecanoromycetes. Finally, the study by Hashimoto & al. (2021) showed that S. difformis and S. resinae belong to Xylonomycetes, a group which was morphologically re-circumscribed to comprise a single family (Xylonaceae) with four genera (Sarea, Trinosporium, Tromera, and Xylona). Although Tromera has been considered a synonym of Sarea based on the superficial resemblance of the sexual morph, these authors showed that they are distinct genera and Tromera should be resurrected to accommodate T. resinae. However, Mitchell & al. (2021) stated that Tromera A. Massal is an invalid name (Art. 38.1), the earliest available name being Zythia Fr.
7) Strangospora Körb.- The taxonomy of this small genus, also after the segregation of Piccolia, is rather poorly known. Schmull & al. (2011) suggest that at least S. pinicola is part of Ostropomycetidae, being related to Schaereria fuscocinerea, but without significant support. Currently, the genus is included in the Strangosporaceae, of uncertain position within the Pezizomycotina.
The key includes all species known to occur in Italy (Nimis 2016), plus a few species known from neighbouring countries in the Alps (Nimis & al. 2018) and which should be looked for in Italy, for a total of 15 species.

References

Bellemere, A. (1994). Documents et commentaires sur l’ultrastructure des asques polyspores des Acarospora, de quelques genres de la famille des Acarosporaceae et de genres similaires. Bul. Linnean Soc. Provence, 45: 355-388.
Hafellner J. 1994b. On Biatoridium, a resurrected genus of lichenised fungi (Ascomycotina, Lecanorales). Acta Bot. Fenn., 150: 39-46, 1994.
Hafellner J. 2004. A revision of Maronella laricina and Piccolia ochrophora. Symb. Bot. Upsal., 34, 1: 87-96.
Hashimoto A., Masumoto H., Endoh R., Degawa Y., Ohkuma M. 2021. Revision of Xylonaceae (Xylonales, Xylonomycetes) to include Sarea and Tromera. Mycoscience, 62, 1:47-63.
Hawksworth D. L., Sherwood,M. A. 1981. A reassessment of three widespread resinicolous discomycetes. Can. J. Bot., 59: 357-372.
Hodkinson B. P., Lendemer J. C. 2011. The orders of Ostropomycetidae (Lecanoromycetes, Ascomycota): recognition of Sarrameanales and Trapeliales with a request to retain Pertusariales over Agyriales. Phytologia, 93, 407-412.
Miadlikowska J., Kauff F., Högnabba F., Oliver J.C., Molnár K, Fraker E., Gaya E., Hafellner J., Hofstetter V., Gueidan C., Otálora M.A.G., Hodkinson B., Kukwa M., Lücking R., Björk C., Sipman H.J.M., Burgaz A.R., Thell A., Passo A., Myllys L., Goward T., Fern 2014. A multigene phylogenetic synthesis for the class Lecanoromycetes (Ascomycota): 1307 fungi representing 1139 infrageneric taxa, 317 genera and 66 families. Mol. Phylogenet. Evol., 79: 132-168.
Mitchell J.K., Garrido-Benavent I., Quijada L., Pfister D.H. 2021. Sareomycetes: more diverse than meets the eye. IMA Fungus, 12:6. https://doi.org/10.1186/s43008-021-00056-0
Nimis P.L. 2016. The lichens of Italy. A second annotated catalogue. EUT, Trieste, 740 pp.
Nimis P.L., Hafellner J., Roux C., Clerc P., Mayrhofer H., Martellos S., Bilovitz P.O. 2018. The Lichens of the Alps. An Annotated Catalogue. Mycokeys, 31: 1-634.
Poelt J. 1974. Classification. In: V. Ahmadjian, M. E. Hale (eds.), The lichens. London: Academic Press.
Reeb V., Lutzoni F., Roux C. 2004. Contribution of RPB2 to multilocus phylogenetic studies of the euascomycetes (Pezizomycotina, Fungi) with special emphasis on the lichen-forming Acarosporaceae and evolution of polyspory. Molec. Biol. Evol., 32: 1036-1060.
Schmull M., Miadlikowska J., Pelzer M., Stocker-Wörgötter E., Hofstetter V., Fraker E., Hodkinson B.P., Reeb V., Kukwa M., Lumbsch H.T., Kauff F., Lutzoni F. 2011. Phylogenetic affiliations of members of the heterogeneous lichen-forming fungi of the genus Lecidea sensu Zahlbruckner (Lecanoromycetes, Ascomycota). Mycologia, 103, 5: 983-1003.

Last modified: August, 20, 2021

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