taxonID	type	description	language	source
8216B8D6441E582F8C4A6246820A53C0.taxon	description	Fig. 15 A	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
6C109797D84E5511A6E4EF002C31A16D.taxon	description	Fig. 15 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
DFC421925F7E551186E7B465E65644F2.taxon	description	Figs 15 C, 16 A, 17	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
9725B022BF905AFA8723674317E7B365.taxon	description	Fig. 15 D	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
D99900F80113563E9B0C8A4F7609E136.taxon	description	Fig. 15 E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
B0D6C74F057B54819C6727677100FF9E.taxon	type_taxon	Generic type. Adustochaete rava R. L. M. Alvarenga & K. H. Larss. Adustochaete was described to encompass two Heterochaete - like species, A. rava and A. interrupta. These species turned out to be phylogenetically distant from the generic type of Heterochaete, H. andina, as well as other Heterochaete s. lato species reclassified among Eichleriella, Hirneolina, Heteroradulum, and Tremellochaete (Alvarenga et al. 2019), and were therefore placed in their own genus. Subsequently, four more species were introduced in Adustochaete, viz. A. nivea from Brazil (Hyde et al. 2020), as well as A. yunnanensis, A. albomarginata, and A. punctata from China (Li and Zhao 2022; Dong et al. 2024). Here we add six more species to the genus and reintroduce A. rava and A. nivea based on more extensive material from Argentina (for the species-level phylogeny of the genus, see Figs 13, 14). See also remarks on Exidia punctata under Excluded and insufficiently known species below. Although Adustochaete spp. form a strongly supported clade (Figs 1, 2) and are clearly separated from the rest of the genera in the Exidia clade in our phylogenies, the morphological definition of Adustochaete is not easy. Originally, the genus was defined as containing monomitic, cystidia-bearing species with grayish or brownish, spinulose or tuberculate hymenial surface and four-celled, ellipsoid-ovoid or nearly obconical basidia which possess thick sterigmata (Alvarenga et al. 2019). However, expanding Adustochaete with more species described makes it difficult to maintain the original concept of the genus. In particular, adding four completely or nearly smooth species (A. fumida, A. gloeoapicata, A. hiemalis, and A. scalena) blurs the borders between Adustochaete and some other genera containing the former Exidiopsis and Heterochaete spp. Of them, the reinstated Leiostroma is strongly reminiscent of Adustochaete. Both genera include resupinate species with spinulose or smooth, grayish or brownish, easily crumbling, arid basidiomata and richly encrusted hyphae. Moreover, their hyphae and hymenial cells are sometimes brownish, evidently due to the color of the cytoplasm. The contents of these coloured cells clearly stain in CB (cyanophilous) in Adustochaete spp. while they normally stay unchanged or show only a weak cyanophilous reaction in Leiostroma. Another trait separating the two genera is the crystalline incrustation on hyphae. Species of both genera produce abundant, small, angular or sand-like (fine-grained) crystals; these crystals, however, mostly remain discrete in Adustochaete and often fuse together and produce continuous shields, especially on basal hyphae and apical branches of hyphidia, in Leiostroma. Furthermore, Leiostroma spp. have well-differentiated basidia-bearing hyphae which are as a rule wider than the surrounding subhymenial hyphae; no such differentiation was observed in the Adustochaete spp. studied by us. Differences between Adustochaete and another similar-looking genus, Proterochaete, are more obvious. Proterochaete spp. possess tougher basidiomata than those of Adustochaete, which consist of densely arranged, partly glued hyphae. Along with angular crystals, hyphae and hymenial cells of many Proterochaete spp. also bear brownish, cyanophilous grains fusing in large amorphous bodies in mature and especially senescent basidiomata. See further remarks under Adustochaete hiemalis.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
4BA78139DC635873BCC88C1A04604FBF.taxon	description	Fig. 15 F	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
DB577AA417295482861592B3C91BE1DD.taxon	description	Fig. 15 G	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
8D87440FC0675EB4943FE8015ABD5954.taxon	description	Figs 15 H, 16 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
721BFD3FAB4B5682905B34280079853F.taxon	type_taxon	Generic type. Tremella thuretiana Lév. The genus is introduced here to accommodate two Exidia s. lato species, E. repanda and E. thuretiana, which cluster together outside of the main Exidia clade (Figs 1, 2). These species differ from almost all genuine Exidia species in having a rather loose epihymenial layer which is composed of smooth (i. e. non-encrusted) apical branches of hyphidia. Moreover, E. repanda and E. thuretiana do not produce spine-like projections on the hymenial surface, which are characteristic of the great majority of Exidia s. str. species. See further remarks under Exidia. The exidioid representatives of Ulocolla (i. e. Exidia saccharina and related species) often lack these projections, too. However, the epihymenial layer in these species consists of variably thick-walled and often inflated, pigmented (brownish) hyphidia. Moreover, jelly-like species of Ulocolla occur exclusively on coniferous hosts while the two Descidia spp. are restricted to angiosperm wood.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
47ECF90A050B535FB8049428734DAA86.taxon	description	Figs 15 I, 16 C, 18	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
2AE58E1CCB5553E38DB1E52D86582621.taxon	type_taxon	Generic type (lectotype). Eichleriella incarnata Bres. (selected by Burt 1915: 743). In our earlier treatment of Eichleriella and related genera (Malysheva and Spirin 2017), the genus Amphistereum was introduced to encompass two stereoid, dimitic species, A. leveilleanum and A. schrenkii. In the ITS – LSU-based phylogeny, they clustered with Eichleriella s. str., although without statistical support, and so were placed in a separate genus. Our current data (Figs 1, 2) show that A. leveilleanum is part of a strongly supported Eichleriella clade. Amphistereum is therefore considered a later synonym of Eichleriella.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
B7EA698807505530958D8C6DAD3583DC.taxon	description	Fig. 15 J	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
11D617F470915C85885BD5BA3E19BE23.taxon	type_taxon	Generic type. Elmericium alabastrinum Spirin & Malysheva. This genus was recently introduced as monotypic, with the East Asian E. alabastrinum as the sole species (Spirin et al. 2025). Here we expand it with the newly described E. spinosum from Africa (see Suppl. material 5).	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
E5F049CE585E561B8EF727966D5687BB.taxon	description	Fig. 36 H	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
5B6B20FB3DF159CE98D36951030F03D2.taxon	description	Fig. 16 D, E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
18E0648FCE6D5AE7B64AC7FC9855AAAD.taxon	description	Fig. 19 A	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
9F38A79DE5755655ACED4153828124C7.taxon	description	Figs 16 F, 19 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
AC0ADB04B0D95CE49B7E70203F5BFE79.taxon	description	Figs 19 C, 20 A	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
80B1606A17C055CDA5E9A86E27BFBD62.taxon	description	Figs 19 D, 20 B, 21	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
6E45EB4649405BB89512A0C84DB571A0.taxon	description	Figs 19 E, 20 C, 22	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
74193FDE0917586CBE2488E91EB2F2A8.taxon	description	Fig. 19 F	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
B80B37C83F715AA1ADB9F4EF99E00BF6.taxon	description	Figs 19 G, 19 H, 20 E, 20 F	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
3342BF438EC054E6B4A45B2FCCF320AD.taxon	description	Figs 19 I, 20 D	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
284045812D8E5024941E0753E4EDBC18.taxon	description	Figs 20 G, 23 A, 23 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
1937603E4290500EB2AD1FCC82A486F8.taxon	description	Fig. 23 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
12A0AC9A5D3B55628DC51D0BAE8D0E38.taxon	description	Figs 20 H, 23 C	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
8F81AAE3FB83541393A6228EF96FB766.taxon	description	Figs 23 D, 24 A	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
83068EC904035A79AB35144CE43C688B.taxon	description	Fig. 23 E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
37245CC175255648B0C9B757B32E537E.taxon	description	Figs 23 F, 24 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
5FDAC009473C5930AECA0DFC70462126.taxon	description	Fig. 23 G	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
ED5154B274405AAD95BFC8B17C67324E.taxon	description	Figs 23 H, 24 C	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
1539721AB6395FE9AD529AB78F82FFE3.taxon	description	Figs 23 I, 24 D	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
EFC09F504C8A5728A2D916FCEE2E09F2.taxon	description	Fig. 24 E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
E67E65E820B458B3A92740859FFCA319.taxon	description	Figs 23 J, 24 F	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
26560DEFADDF5E4DA51E9F4652B44F41.taxon	description	Figs 25 A, 26, 27 A, 27 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
0CC5F046C2BA5CD28DC74789F1007F4D.taxon	description	Figs 25 B, 27 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
C03165B89CC35F50B1628683E17C1C90.taxon	type_taxon	Generic type. Exidia effusa Bref. Our data show that the generic type of Exidiopsis, E. effusa, is not closely related to any other previously described Exidiopsis species. Instead, it is sister to Heteroradulum (Figs 1, 2; see Results) and, probably, Heterochaete s. typi (Malysheva and Spirin 2017); however, their phylogenetic relationships must be investigated further, with a much larger taxon sampling than used in the present study. In the current scope, the genus contains two species, E. effusa and E. perflua, introduced below. These two species differ from other species previously assigned to Exidiopsis in having pale and thin, waxy-gelatinous basidiomata, usually with a pink or lilac hue, ellipsoid-ovoid basidia with a clearly tapering base, long and curved basidiospores, as well as in lacking cystidia and distinctive encrustation. The taxonomic history of the genus is complicated. Exidiopsis was first introduced by Brefeld (1888) as a subgenus of Exidia for a single species, Exidia effusa. However, the species name was given in his text as ‘ Exidiopsis effusa ’, and this naming became the source of subsequent controversy. Donk (1958) correctly cited Brefeld’s binomial as Exidia effusa and considered it as validly published. However, he changed his mind eight years later (Donk 1966) and cited Brefeld’s species as Exidiopsis effusa Bref. ‘ n. v. p. ’ (= not validly published). The reasons for this later interpretation were not provided. Most likely, Donk switched to a more literal interpretation of Brefeld’s description and considered Exidiopsis effusa as a new species described by Brefeld without introducing the appropriate genus for it, i. e. as invalid. This viewpoint was accepted by Index Fungorum and MycoBank (as of December 1 st, 2025), both listing Brefeld’s binomial as the invalidly published Exidiopsis effusa. However, Brefeld’s explanations in the protologue of Exidiopsis effusa clearly show that he found no grounds to raise Exidiopsis to the genus rank and even argued against this option (Brefeld 1888: 94 – 95). It is therefore evident that Brefeld ascribed his new species to Exidia and merely followed the fashion of the time in using subgenera along with generic names in the species descriptions. Hence, Exidia effusa. Vuillemin (1890: 30) was the first author who used the name Exidiopsis at the genus level. He introduced a new species under the name Exidiopsis quercina and compared it with ‘ Exidiopsis effusa Bref. ’ By using the latter binomial, Vuillemin in fact created a new combination, Exidiopsis effusa (Bref.) Vuillemin, as was already noted by Donk (1958). Donk (ibid.) further stated that the new species E. quercina and the new combination E. effusa were not validly published by Vuillemin because he ‘ did not mention separately’ the generic name, i. e. Exidiopsis, at its new rank. However, this is not necessary under the current version of the Code: the indication ‘ Exidiopsis effusa Bref. ’ in Vuillemin’s description constitutes an indirect reference not only to Exidia effusa Bref. (Art. 38.14) but also to Exidiopsis as a validly published subgenus of Exidia (Art. 41.3). In other words, Vuillemin simultaneously combined Exidia effusa in Exidiopsis and raised the latter name to genus rank, thus fulfilling the requirements of Art. 41.2. Therefore, the generic name must be cited as Exidiopsis (Bref.) Vuillemin, while Exidiopsis (Bref.) Möller is merely its later isonym.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
2AE2B030B61C5255949F43361D513DED.taxon	description	Figs 25 C, 27 C, 28	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
0170A89F61B45B0F9C7DE9D16E17A72C.taxon	type_taxon	Generic type. Thelephora acerina var. abietis Fr. (= Corticium abietis (Fr.) Romell) (see comments below). As reintroduced here, Leiostroma encompasses four species having soft, easily crumbling, effused basidiomata with more or less pronounced tints of gray or brown. The same colouration is also characteristic for the contents of (at least some) hyphae and hymenial cells. All included species lack cystidia and possess very characteristic, abundant, hyaline, sand-like crystalline encrustation. These encrusting bodies are often very densely arranged, which makes microscopic structures difficult to observe. They form continuous shields on subicular hyphae and, in mature basidiomata, also on subhymenial hyphae and occasionally on hymenial cells (Fig. 28). These features, as well as the lack of cystidia, separate Leiostroma spp. from the similar-looking smooth Adustochaete species. Moreover, basidia-bearing hyphae are well differentiated in Leiostroma and usually clearly wider than subhymenial hyphae; in Adustochaete spp., no perceptible difference between these hyphal types was observed. Some Proterochaete spp. (P. furfurosa, P. letendreana, and P. mucedinea) macroscopically similar to Leiostroma can be differentiated by their more densely arranged, partly glued hyphae (vs. spaced in the latter genus), as well as the presence of cystidia (except for P. letendreana) and granular, brownish, cyanophilous deposits on hyphae and hymenial cells. Differences between the two genera are discussed in more detail under Proterochaete. Mature, faded basidiomata of Tegmenticium peritrichum can be mistaken for Leiostroma spp.; however, it has cystidia and is devoid of incrustation on hyphae and hymenial cells. Here we reinstate the generic name Leiostroma to encompass, to some extent, a species, formerly known as Exidiopsis calcea in North Europe, as well as three closely related species from the southern part of Europe, Macaronesia and Africa. Liu et al. (2022) uncritically took E. calcea and, without clarifying its identity, combined it in their newly described genus, Alloexidiopsis. The genus was typified with the simultaneously introduced A. schistacea, an effused, Heterochaete - like species from the southern part of China. The latter species is probably identical with Heterochaete cretacea Pat. from Vietnam (Patouillard 1924). Although it was shown by Liu et al. (2022) as forming a strongly supported clade with the so-called E. calcea and several other species, the question about their relationships, in our opinion, cannot be solved solely on the basis of the ribosomal gene-based phylogenies. Available ITS sequences of A. schistacea reveal a relatively low similarity (less than 94 %) with E. calcea s. auct. and three other species dealt with below. LSU sequences of this species provide no additional information because they show A. schistacea to be very close to and, at the same time, equally distant from E. calcea s. auct. with its closest relatives on one hand and Heteroradulum spp. on another (98.5 – 98.7 % similarity). Due to the lack of the specimens suitable for obtaining additional genetic markers, we leave the question about the phylogenetic placement of A. schistacea open. In the following paragraphs, we argue for resurrecting the genus name Leiostroma for E. calcea s. auct. and its closest relatives; our arguments in favor of discarding the species name Thelephora calcea Pers. (basionym of E. calcea) are provided under Leiostroma farinellum. The genus Leiostroma was introduced by Fries (1819) without any species assigned to it (“ Species plures ”). Two years later, Fries (1821) lowered the rank of Leiostroma to the section in the genus Thelephora and described six species therein, i. e. Thelephora acerina, T. cinerea, T. fallax, T. maculaeformis, T. amphibolia, and T. sterilis. It seems this list reflects his original views on the scope of Leiostroma because the description of the section in Systema expands the earlier generic description of Leiostroma and does not contradict it. Donk (1957) treated Leiostroma sensu Fries 1821 as a subgenus of Thelephora and typified it with T. maculaeformis. He argued that T. maculaeformis was a ‘ constant member’ of Leiostroma, while two other candidates for typification, T. cinerea and T. acerina, had been subsequently removed by Fries himself and placed in other sections or genera. Later Donk (1963) detected that Leiostroma was published as a genus already in 1819; he, however, maintained his earlier typification of it with T. maculaeformis, providing no new arguments. The type material of T. maculaeformis was studied by Eriksson (1950) who found it to be conspecific with Peniophora polygonia (Pers.) Bourdot & Galzin. The latter species is a member of Peniophora in the current sense (Hallenberg et al. 1996). Before 1982, Donk’s typification looked harmless because Leiostroma was considered a devalidated name, i. e. that published prior to Fries’ Systema Mycologicum and therefore having no priority over generic names introduced afterwards. However, after changing the starting point for validly published fungal genera in 1982, Leiostroma becomes an older name for Peniophora, a large and widely accepted genus of crust fungi. This name change looks very unfortunate, and we therefore argue in favor of abandoning Donk’s typification and conserving Leiostroma with another generic type. Under Code Art. 10.2, any of the six mentioned species mentioned by Fries (1821) is suitable for lectotypification of the genus. However, the first five species are currently classified among well-established genera of corticioid fungi, i. e. Dendrothele Höhn. & Litsch. (T. acerina), Peniophora Cooke (T. cinerea, T. fallax, and the already mentioned T. maculaeformis), and Phanerochaete P. Karst. (T. amphibolia). Selecting any of these species as a lectotype of Leiostroma would result in discarding one of these currently accepted corticioid genera (Dendrothele, Peniophora, or Phanerochaete) from use because it is older than any of them. As far as we know, no authentic specimens of the sixth species, Thelephora sterilis, exist. In the subsequent reintroduction of the section Leiostroma, Fries (1828: 224) retained four species from the previous treatise (T. acerina, T. maculaeformis, T. amphibolia, and T. sterilis) and added seven more species, i. e. T. corrugata, T. laevigata, T. episphaeria, T. bufonia, T. circinata, T. typhae, and T. epiphylla. Again, choosing any of these species as the generic type of Leiostroma is problematic: T. corrugata and T. episphaeria are currently treated under Hydnoporia, T. laevigata is a species of Amylostereum, T. circinata is the generic type of Sarcopodium (Ascomycota), T. typhae is the generic type of Epithele, and T. epiphylla is that of Athelia. All these currently accepted generic names (except Athelia and Sarcopodium) are younger than Leiostroma. As for T. bufonia, its identity remains uncertain. There are five specimens in Persoon’s herbarium in Leiden identified as T. bufonia, representing various bark-inhabiting fungi. It seems that Fries was uncertain about identity of this species, and it was certainly not the source of his concept of Leiostroma. This leads us to a conclusion that there are no species associated with Leiostroma which could be suitable for the typification of this genus without causing problems for the current classification of fungi. Therefore, we have to return to the original description of the genus by Fries in 1819. The Code Art. 10.2 provides us with a choice: either to select a lectotype of Leiostroma among the species associated with its later reintroduction as a section in the genus Thelephora, or to choose the type otherwise. The first option looks inconvenient because – as we demonstrated above – it would lead to a disposal of the currently accepted and well-defined genera. So, we follow the second option aligning it, as much as possible, with Fries’ concept of Leiostroma as he developed between 1819 and 1828. In both Systema and Elenchus, Fries listed Thelephora acerina as the first species in the section Leiostroma. He most likely viewed it as the most “ typical ” representative of the section because the most important features of its introduction (basidiome shape and consistency, hymenium configuration) in Systema repeat those in the section’s description. The species was introduced with four varieties, of which the first, T. acerina var. abietis, is of special interest for the present study. It certainly refers to a taxon macroscopically similar to Dendrothele acerina but occurring on Picea and clearly implies a widely distributed conifer-dwelling species which was treated as Sebacina or Exidiopsis calcea after Bresadola (1898) and Wells (1961). In our opinion, the latter name is inapplicable to T. acerina var. abietis (see remarks under Leiostroma farinellum) and must be interpreted otherwise. Romell (1895) was the first who clarified the identity of var. abietis, and we see no reasons to reject his interpretation. He raised it to the species level; however, his Corticium abietis is preceded by Xerocarpus farinellus by Karsten (1882) which we reinstate as a species of Leiostroma below. Nevertheless, this fact does not make T. acerina var. abietis unsuitable for the typification of the genus. We therefore propose to conserve it as a type of Leiostroma. A conservation proposal has been submitted to the Nomenclatural Committee for Fungi.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
ADE2A655E6055883BD47DEC8DA24F19A.taxon	description	Figs 25 D, 27 D	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
69007F3F317655FA90B506D09EDF72F0.taxon	description	Figs 25 E, 27 E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
A6C281944F6F506CB3962F9814D3F784.taxon	description	Fig. 27 F	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
C5C6998461145A2EB3E71A97C1B72A96.taxon	description	Figs 25 F, 29	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
20257706F16F50EA8B9A63C0F4C5CFF3.taxon	type_taxon	Generic type. Pholiobasidion senex. Our data show that Pholiobasidion is sister to the rest of the Auriculariaceae (Figs 1, 2). Whether it belongs to the family or should be treated separately from the Auriculariaceae is a question which cannot be solved without a much denser sampling among the residual Auriculariales. Morphologically, Pholiobasidion is strikingly similar to Basidiodendron spp. due to its small, broadly ellipsoid or subglobose basidia grouped together and covered by remnants of collapsed hymenial cells. However, the remaining morphological traits point elsewhere. In particular, there are no differentiated fishbone-like basidia-bearing hyphae in Pholiobasidion which are so characteristic of the core Basidiodendron spp. Moreover, cystidia of P. senex lack oily, strongly cyanophilous contents and should thus be considered as normal cystidia. In contrast, all species of Basidiodendron possess easily detectable gloeocystidia. Basidiospores of Pholiobasidion have a conventionally located, rather small and symmetric apiculus (Fig. 29) – they therefore look quite different from the spores of Basidiodendron (cf. Spirin et al. 2020, 2021). Phylogenetically, the core Basidiodendron spp. are related to Protohydnum and form a clade which is very distant from the Auriculariaceae (Spirin et al. 2025).	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
43BF5EAEF8DB5A01A59AD51ED2CCBDB8.taxon	description	Figs 31, 32 A	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
9C2AD4D7F6CB554E9AA7CBFB6BD3B710.taxon	description	Fig. 32 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
B5A14CA17EA15683B28DC87D067001E8.taxon	description	Fig. 32 C	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
DB8FAE903965554F896A431B723F35A0.taxon	description	Figs 30, 32 D, 33 A, B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
A1E6D424386053BB859ED1B6B71E28C5.taxon	description	Fig. 32 E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
ED3EBB2C8FA95FE0B1C228C15AC42128.taxon	description	Fig. 32 F	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
F740719BBD585ECC867AC9EA27CC6276.taxon	description	Fig. 32 G	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
63614E48E05B5320A99CF50A8D580ADB.taxon	type_taxon	Generic type. Sebacina adusta Burt. The genus Proterochaete was introduced as monotypic, with Sebacina adusta as the sole species and generic type (Alvarenga et al. 2019). It was justified via phylogenetic evidence which showed that the species is quite isolated from the rest of the Auriculariaceae genera sampled at the time. Morphologically, Proterochaete was separated from the rest of the Exidiopsis - like taxa because of a highly peculiar combination of macroscopic traits in the type species, i. e. spinulose hymenophore and partly detaching, fimbriate and occasionally rhizomorphic basidiome margin. However, our current data impel us to expand the genus with ten more species, none of which has the aforementioned macroscopic features. In the current scope, Proterochaete can be separated from the other Exidiopsis / Heterochaete - like genera of the Auriculariacae (Adustochaete, Eichleriella, Exidiopsis s. str., Heteroradulum, Leiostroma, and Ulocolla pr. p.) due to the following characters. First, all but two Proterochaete spp. possess abundant, small, as a rule angular crystals on their hyphae and hymenial cells. This feature rules out Eichleriella, Exidiopsis, Tegmenticium, and Ulocolla spp. Basidia of many Proterochaete spp. vary from ellipsoid-ovoid to obconical; in the latter case, they are reminiscent of the basidial cells in Heteroradulum. They are, however, devoid of the well-developed basal stalk characteristic of Heteroradulum spp. Moreover, most Heteroradulum spp. are dimitic while all species of Proterochaete are strictly monomitic. Differences between Proterochaete and Adustochaete are discussed under the latter genus. As for Leiostroma, it differs from the outwardly similar Proterochaete spp. (P. africana, P. furfurosa, P. letendreana, and P. mucedinea) in having softer basidiomata consisting of rather loosely arranged, not glued hyphae which often bear solid crystalline incrustation. In addition, hyphae and hyphidia of the listed Proterochaete spp. bear brownish amorphous granules well visible in CB (Fig. 30); these deposits are especially common in mature and senescent basidiomata where they fuse together and form large, amorphous, distinctly cyanophilous concretions. Moreover, most Proterochaete spp. have true cystidia and basidia-bearing hyphae of some species are poorly differentiated from the surrounding subhymenial hyphae. In contrast, all Leiostroma spp. described above are acystidiate and their basidia-bearing hyphae are wider than the subhymenial ones and thus easily detectable. See further remarks under P. letendreana. Proterochaete abstrusa and P. adusta are the only species in the genus with a somewhat deviating morphology. They are totally devoid of a coarse crystalline encrustation, and their mature basidiomata are at least partly gelatinized, not waxy-arid as in other Proterochaete species. They are, however, otherwise very similar to other representatives of the genus, especially to P. macrogyna and P. paniculata. The superficially similar Eichleriella spp. can be separated from the mentioned Proterochaete species due to a distinctive subicular layer consisting of variably thick-walled, predominantly subparallel, spaced (not glued) and often brownish hyphae.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
3C01854D21E6541586E3DCCFAEF68BC3.taxon	description	Fig. 32 H	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
1206350529225C39A1B92EE061C2368D.taxon	description	Fig. 34	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
FC0E283DE01C52628A05BF42BF1B87EC.taxon	type_taxon	Generic type. Scrupulispora perparvula. This genus is introduced here as monotypic, with S. perparvula as the single species. It belongs to Auriculariaceae and is probably related to Oliveonia (Fig. 2). The two genera share some important morphological traits, such as ephemeral, inconspicuous basidiomata, tapering hymenial cystidia, and small basidia with rather long sterigmata. The presence of acanthophyses in Scrupulispora makes it similar to Heteroacanthella. However, all known Heteroacanthella species are devoid of cystidia and their basidia are one-celled, bearing one or two sterigmata (Oberwinkler et al. 1990; Roberts 1999). Moreover, the basidiospores of Oliveonia and Heteroacanthella spp. are smooth; in S. perparvula, their wall usually bears small, sand-like, cyanophilous, irregularly distributed deposits. We were able to observe this encrustation in both turgid and half-collapsed, empty spores. Therefore, we suppose that the presence of these deposits is more or less permanent, and it may serve as a diagnostic trait of S. perparvula. Among the Auriculariales, only a few Basidiodendron spp. also have ornamented basidiospores. They, however, do not belong to the Auriculariaceae (Spirin et al. 2021, 2025).	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
E11E6F853B715E79883BF034A6738C55.taxon	description	Figs 33 C, 35, 36 A	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
305E479CB8225585B0B94FAD2A6B73A5.taxon	type_taxon	Generic type. Sebacina peritricha Bourdot & Galzin. This genus is introduced here for a single species, Exidiopsis (Sebacina) peritricha, which is currently synonymized with E. effusa. Our data (Figs 1, 2) show that these species should be treated separately and that they are not closely related. Tegmenticium peritrichum is different from other European species formerly treated under Exidiopsis due to its well-developed cystidia, as well as its rather small basidia and basidiospores. Its mature basidiomata are clearly gelatinized and covered by a whitish-grayish, easily removable deposit. Thus, they can be mistaken for E. effusa. The latter species, however, lacks cystidia and has larger basidia and, in most specimens, longer basidiospores. Moreover, it possesses spine-like outgrowths on its hymenial surface, although they can be detected only in fresh or rehydrated specimens. Differences of T. peritrichum from the outwardly similar Exidia repleta and E. saturata are discussed above, under E. repleta. Proterochaete abstrusa occasionally bears cystidia which are similar to those of T. peritrichum. However, P. abstrusa can be easily recognized due to its slenderer basidiomata, larger basidiospores and basidia, as well as thicker sterigmata. See further notes under Ulocolla corticioides.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
A568E1E54F8E58539A14FB97E39BDC5A.taxon	type_taxon	Generic type. Exidia saccharina Fr. (selected by Clements and Shear 1931: 342). The genus Ulocolla was described by Brefeld (1888) for two species, U. saccharina and U. foliacea. The first species was explicitly based on E. saccharina by Fries, while the second one was often considered as a recombination of Tremella foliacea Pers. (currently Phaeotremella foliacea (Pers.) Wedin et al., Tremellales). Brefeld’s description of U. foliacea clearly refers to U. saccharina with more distinctly lobate, foliaceous basidiomata and not to P. foliacea. However, his reference to Persoon’s T. foliacea in the beginning of the Ulocolla chapter of his book (Brefeld 1888: 95) makes it, formally, a new combination based on Persoon’s species. Clements and Shear (1931) selected E. saccharina as the generic type of Ulocolla. As reintroduced here, Ulocolla encompasses seven species with rather divergent macroscopic traits. Three of them (U. pinicola, U. saccharina, and U. subrepanda) were classified in Exidia, two (U. grisea and U. griseobrunnea) in Exidiopsis, and one more (U. corticioides) was considered merely a variety of the broadly defined Sebacina calcea (as var. corticioides). These species groups have never been discussed in connection to each other before or recognized as belonging to a joint monophyletic lineage. Our data firmly place them together (Figs 1, 2). Despite their various macroscopic habits, Ulocolla spp. share several important anatomical traits which allow morphological recognition of this genus. First, basidiomata of most species show more or less pronounced brown pigmentation caused by yellowish or brownish cytoplasm of hyphae and hymenial cells and, in most cases, by the presence of amorphous yellowish-brownish exudates cementing apical branches of hyphidia and sometimes spreading among hymenial cells. Second, Ulocolla spp. have much more irregularly inflated hyphae than any other taxa treated in this study (except for Exidia repleta, E. saturata, and Exidiopsis s. str. spp.), which often show rather sharp transitions between normally looking, narrow and strongly widened, inflated hyphal segments. All Ulocolla spp. have ellipsoid-ovoid, often obliquely septate basidia sometimes having a tapering, stalk-like base and bearing slender sterigmata. Four exidioid Ulocolla species (U. orbiculata, U. pinicola, U. saccharina, and U. subrepanda) differ from the similar species of Exidia s. str. by the lack of granular encrustation on their hyphae and hyphidia. Moreover, they have hyphidia with variably thick-walled, brownish and often strongly inflated stems. No such structures have been observed in the brown-colored Exidia spp. (E. candida and the E. recisa complex). In turn, hyphidia of the superficially similar Descidia repanda have narrow, hyphoid, rather evenly outlined stems.	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
641E65D55E515C6BA5606B53AFF4C93A.taxon	description	Figs 33 D, 36 B	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
DD2F0ACFD4C159B9996C93C5E507B3D6.taxon	description	Figs 36 C, 37	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
E5BB709CCCDA5CE1AAF197E2D05FB308.taxon	description	Figs 33 E, 36 D	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
ED3282CAE3D05C3AA7E4A05C445AE0F1.taxon	description	Fig. 36 E	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
36520E82065259A68431793084DD23ED.taxon	description	Figs 33 F, 36 F, 38	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
6EBF40BD052951099496856489992C47.taxon	description	Figs 33 G, 36 G	en	Spirin, Viacheslav, Malysheva, Vera, Schoutteten, Nathan, Savchenko, Anton, Rivoire, Bernard, Olsson, Jan, Læssøe, Thomas, Ryvarden, Leif, Grootmyers, Django, Kulju, Matti, Vlasák, Josef, Vignale, María Victoria, Viner, Ilya (2026): Exidia and Exidiopsis (Auriculariales, Basidiomycota): a reconsideration. IMA Fungus 17: e 189042, DOI: 10.3897/imafungus.17.189042
