<8) MycoKeys MycoKeys 120: 339-392 (2025) DOI: 10.3897/mycokeys.120.155492 Research Article Additions to the taxonomy of the Auriculariales (Basidiomycota) with pedunculate basidia Viacheslav Spirin'’?, Vera Malysheva’, Ilya Viner?, Renato Lucio Mendes Alvarenga”, Tine Grebenc™, Gérald Gruhn®®, Anton Savchenko”, Django Grootmyers®®, Leif Ryvarden®, Josef Viasak'’™®, Karl-Henrik Larsson™’2©, R. Henrik Nilsson’® eo ON DW oO FP WO YS - Department of Biological and Environmental Sciences, Box 463, University of Gothenburg, 405 30 Gothenburg, Sweden Finnish Museum of Natural History, University of Helsinki, PO Box 7, 00014 Helsinki, Finland Shatelena str. 20/75, 194021 St. Petersburg, Russia Departamento de Micologia, Universidade Federal de Pernambuco (UFPE), Avenida da Engenharia s/n, Recife, Pernambuco, 50740-600, Brazil Slovenian Forestry Institute, Vecna pot 2, 1000 Ljubljana, Slovenia Office National des Foréts, 5 avenue Mirandol, 48000 Mende, France Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, Netherlands Department of Ecology and Evolutionary Biology, University of Tennessee, 1406 Circle Drive, Knoxville, Tennessee 37996, USA Institute of Biological Sciences, University of Oslo, PO. Box 1045, Blindern, N-0316 Oslo, Norway 10 Biology Centre, Academy of Sciences of the Czech Republic, Branigovské 31, CZ 37005, Ceské Budéjovice, Czech Republic 11 Natural History Museum, University of Oslo, RO. Box 1172, Blindern, 0318 Oslo, Norway 12 Gothenburg Global Biodiversity Centre, University of Gothenburg, Box 461, 40530 Gothenburg, Sweden Corresponding author: Viacheslav Spirin (viacheslav. spirin@helsinki.fi) OPEN Qaceess Academic editor: Maria-Alice Neves Received: 10 April 2025 Accepted: 18 July 2025 Published: 19 August 2025 Citation: Spirin V, Malysheva V, Viner |, Alvarenga RLM, Grebenc T, Gruhn G, Savchenko A, Grootmyers D, Ryvarden L, Viasak J, Larsson K-H, Nilsson RH (2025) Additions to the taxonomy of the Auriculariales (Basidiomycota) with pedunculate basidia. MycoKeys 120: 339-392. https://doi. org/10.3897/mycokeys.120.155492 Copyright: © Viacheslav Spirin et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International - CC BY 4.0). Abstract In the present paper, we revise the taxonomy of the Auriculariales having pedunculate (stalked) basidia. In total, sixteen new species from Europe, East Asia, North and South America, and tropical Africa are described. They are classified among the genera Hydropha- na, Mycostilla, Myxarium, Protoacia, Protohydnum, and Protomerulius. In addition, the ge- neric affiliation of eleven extant species is re-established based on phylogenetic and/or morphological evidence. A new genus, Elmericium, is introduced to accommodate a crust- like fungus, E. alabastrinum, from East Asia; phylogenetic data place it in the vicinity of the anatomically similar poroid genera Elmerina and Protodaedalea (Auriculariaceae). The generic description of Protohydnum is amended; in its current scope, the genus encom- passes several species formerly assigned to Bourdotia, Ductifera, and Exidiopsis. Available environmental data point to a wider distribution of some Protomerulius spp. and greater species diversity in the genus than currently surmised from physical fungal samples. Key words: Heterobasidiomycetes, phylogeny, soil sequences, taxonomy Introduction The Auriculariales Bromhead (Agaricomycetes Doweld, Basidiomycota Whittak- er ex R.T. Moore) are an order of wood-inhabiting heterobasidiomycetes with di- versely structured basidia. The great majority of species have four-, more rarely two-celled, longitudinally septate basidia (e.g., Exidia Fr. and Pseudohydnum P. Karst.); at the same time, the order also encompasses fungi with transversally 339 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia (Auricularia Bull.) or obliquely septate (Patouillardina Bres.) basidia, or possess- ing one-celled, non-septate basidia (Oliveonia Donk) (Roberts 1999; Wei and Oberwinkler 2001; Weif et al. 2004). Among the species with longitudinally sep- tate basidia, a large group of taxa have the so-called sphaeropedunculate or myxarioid basidia — in this case, two or four basidial cells are located at the top of a pronounced, stipe-like cell (the “enucleate stalk”). Wells (1964) first argued that sphaeropedunculate basidia represent a taxonomically important morpho- logical trait. However, subsequent research provided different views on the tax- onomic value of these structures (Bandoni 1984; Wells 1994; Roberts 1998). Recent DNA-based studies indicated that the presence of pedunculate (stalked) basidia is informative for the generic reclassification of the Auricular- iales, although its value is not absolute (Wells et al. 2004; Sotome et al. 2014; Malysheva and Spirin 2017; Malysheva et al. 2018; Spirin et al. 2018a, 201 9a, b, c). In the present paper, we expand the existing knowledge of the Auriculariales with stalked basidia: both taxa with sphaeropedunculate (myxarioid) basidia (e.g., Myxarium, Protomerulius) and those with petiolate basidia (e.g., Bourdot- ia, Protohydnum) are dealt with below. To supplement our data on the ecology and distribution of the species, we utilise available (as a rule, yet unnamed) environmental and soil sequences from public repositories. Material and methods Morphological study Specimens from herbaria H, GB, S, O, LE, FH, PC, K, BPI, NY, HBG, LIP LY, TAAM, CWU, LJF, TUF, and URM were studied; herbarium acronyms are giv- en according to Index Herbariorum (https://sweetgum.nybg.org/science/ ih). Microscopic routine and measuring techniques follow Miettinen et al. (2006), and terminology follows Malysheva et al. (2018). All measurements were made in Cotton Blue. No reactions with Melzer’s reagent (amyloid or dextrinoid structures) are known in the studied group. Basidiospores of all species dealt with below are hyaline, smooth, and thin-walled; these fea- tures are not mentioned in the species descriptions. DNA extraction and amplification For DNA extraction protocols, PCR, and sequencing of target loci performed at the Finnish Museum of Natural History, University of Helsinki (Finland), see Viner et al. (2021a) and references therein; for sequencing protocols per- formed at the Komarov Botanical Institute RAS (Saint Petersburg, Russia), see Spirin et al. (2024a). In this study, we amplified the complete nuclear ribosomal DNA ITS1-5.8S-ITS2 (ITS) and partial LSU regions using standard primers (Table 1). Chromatograms were edited and assembled in MEGA X (Kumar et al. 2018); chromatograms exhibiting length variation due to indels were interpreted and assembled as described in Viner et al. (2021b). Addi- tional sequences used in our analyses were retrieved from partial genomes following the methods outlined in Spirin et al. (2022). All newly generated sequences of sufficient quality, including those not used in the phylogenetic analyses, have been submitted to GenBank (Table 2). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 340 — Viacheslav Spirin et al.: Auriculariales with pedunculate basidia Table 1. Primers used in this study. name locus ITS1F CTTGGTCATTTAGAGGAAGTAA ITS, ITS1 LR22 Table 2. DNA sequences obtained for the present study. Specimen / herbarium Country of origin (ISO 3166 code) Species Elmericium alabastrinum Endoperplexa dartmorica Spirin 11781 (0) E. dartmorica Exidiopsis gloeophora J. Nordén 9609 (0) Spirin 5836 (H) Spirin 7958 (H) Viner 2021/289 (H) Gruhn 18-573 (LIP) Spirin 14839 (H) Spirin 15335 (H) RU-LEN RU-KHA Exidiopsis succinea E. succinea m1 Hydrophana fessula mal H. trichiesiana Mycostilla chromatica M. vermiformis a Myxarium cinnamomescens Bulakh LE F-347687 RU-SAK M. crystallinum Viner 2023/26 (H) F M. denticulatum Spirin 17365 (GB) E M. evanidum Spirin 15193 (H) F M. evanidum Spirin 17761 (GB) E al M. fugacissimum Spirin 17971 (H) M. grilletii F M. guianense Gruhn 18-559 (LIP) F M. minutissimum Spirin 16683 (H) M. minutissimum Spirin 17270 (GB) E M. podlachicum Spirin 16589 (GB) E M. varium Spirin 15646 (H) FR Oliveonia fibrillosa Spirin 8257 (H) US-WA Spirin 17688 (GB) Grootmyers 21072014 (H) Burdsall 9422 (LE 23063) Protoacia crispans ep) nw nm) OQ n n @ US-TN US-OH P reliqua Protohydnum album P album Miettinen 19583 (H) US-TN P elevatum RU-SAK P lactescens US-CA P livescens Viner 2022/7 (H) GR P livescens iS) MycoKkeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 Reference Gardes and Bruns 1993 White et al. 1990 White et al. 1990 White et al. 1990 White et al. 1990 Landvik 1996 Hopple and Vilgalys 1994 Hopple and Vilgalys 1994 Vilgalys lab, Duke University (https://sites.duke.edu/ vilgalyslab/ files/2017/08/rDNA-primers-for-fungi.pdf) GenBank / UNITE accession number Spirin 5311 (H) RU-KHA PV241605 MT235621 PV241611 PV241617 PV241618 PV394849 PV462016 PV394846 PV394858 PV241609 PV394865 PV394879 PV394878 PV394881 PV394883 PV394875 PV394847 PV394867 PV394877 PV394873 PV394874 PV394866 PV394876 MT235628 PV394880 PV394850 PV241608 PV241607 PV241606 PV394861 DB PV394871 PV241610 PV241612 PV394848 PV394845 LSU PV241619 MT235602 PV241624 PV241632 PV394849 PV460969 PV394846 PV394865 PV394879 PV394847 MT235607 PV394850 PV241622 PV241621 PV241620 PV394861 UDB PV241623 PV241625 PV394848 PV394845 PV241628 341 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Species P livescens P livescens P livescens P nudum P ocellatum P pallidum Protohydnum sp. Protomerulius amiliavi P. brachysporus P commotus P commotus P commotus P deceptorius P deceptorius P deceptorius P deceptorius P deceptorius P dubius P. madidus P. madidus P. madidus P pertusus P pertusus Specimen / herbarium Country of origin (ISO 3166 code) GenBank / UNITE accession number ITS LSU Miettinen 15872.2 (H) ES PV241614 PV241627 Miettinen 15891.1 (H) ES PV241615 PV241629 Miettinen 16000 (H) ES PV241613 PV241626 Ryvarden 9435 (0) KE PV394856 Larsson 15431 (URM) BR-RO PV241630 Ryvarden 26180 (0) ZW PV241616 PV241631 Vlasak 1808/145 (H) GF PV369164 PV383274 Spirin 16165 (H) FR PV394854 PV394854 Spirin 16288 (H) FR PV394855 PV394855 Spirin 17127 (H) FR PV394870 Spirin 13835 (H) IT PV394857 Spirin 13617 (H) CH PV394851 Spirin 14811 (H) S| PV394853 PV394853 Spirin 14592 (H) S| PV394852 PV394852 Spirin 14651 (H) SI PV394859 Spirin 16764 (H) SI PV394863 Spirin 16863 (H) S| PV394864 Viner 2019/154 (H) Fl PV394872 Spirin 17851 (H) FR PV394882 Spirin 15021 (H) RO PV394860 Spirin 16951 (GB) SE PV394862 Kotiranta 22589 (H) RU-AD PV394869 Spirin 12743 (H) RU-NIZ PV394868 Phylogenetic analyses The newly generated sequences were compiled into five sequence datasets, which were complemented with relevant sequences from the literature. For each dataset, BLAST searches in GenBank and UNITE were used to locate highly sim- ilar public sequences, primarily of the environmental sequencing type, which, if found, were added to the respective dataset. Each dataset was aligned using MAFFT v. 7.520 (Rozewicki et al. 2019) and adjusted manually. Most identical and near-identical sequences were deleted to minimise redundancy. Five sets of phylogenetic analyses were performed: for Fig. 1, both Bayesian inference and maximum-likelihood analysis were undertaken. For simplified versions of Figs 2-5, only Bayesian inference was undertaken. MrModelTest v. 2.4 (Nyland- er 2004) was used to select the model of nucleotide evolution for the Bayesian analysis. As applicable, models were estimated separately for ITS1, 5.8S, ITS2, and LSU. The Bayesian analysis was carried out in MrBayes 3.2.7a (Ronquist et al. 2012). Eight MCMCMC chains were run for 10 million generations with a burn- in of 50%. IQ-TREE v. 2.2.2.6 (Minh et al. 2020) was used to infer the maximum likelihood tree in Fig. 1. IQ-TREE was set to estimate the model of nucleotide evolution and was run using default settings. Ten thousand replicates of ultrafast bootstrap (Hoang et al. 2018) were run to estimate clade support. Sequenced specimens below are marked by an asterisk (*). Results Five datasets were compiled to reconstruct a genus-level topology of the Auric- ulariales, with special focus on taxa with stalked basidia (ITS-LSU dataset), and to assess species diversity in selected genera (four ITS datasets). The multiple MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 349 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 1/92 1/100 0.99/_ 0.95/97 1/100 1/99 1/99 _189 1/80 1/100 1/98; 1/100 1/100 1/100 0.95/82 4/100 -— 1/100 _/100 /100 Protohydnum sp. Viasak 1808/145 Protohydnum ocellatum sp. nov. Larsson 15431 X Protohydnum cartilagineum MG735419 X Exidiopsis livescens Viner 2022/7 X Protohydnum erumpens sp, nov, Savchenko 171123/1515 X Bourdotia galzinii CNU4564 X ‘Ductifera pululahuana' (Protohydnum album) LE23063 Protohydnum pallidum sp. nov. Ryvarden 26180 X Protohydnum elevatum sp. nov. LE F-347688 ‘Ductifera sucina' (Protohydnum lactescens) TAAM192048 er, Basidiodendron eyrei } : 1/100 Basidiodendron cinerellum MW136104 Tremiscus helvelloides DQ520100 X Elmericium alabastrinum sp. nov. Spirin 5311 X Elmerina cladophora MG757509 X _/97 Exidiopsis succinea Spirin 583! Exidia nigricans OM238155 /93 Exidiopsis effusa KX262145 Eichleriella crocata MH178248 Auricularia mesenterica KP729279 Oliveonia fibrillosa Spirin 8257 Protodontia subgelatinosa MK098926 X Myxariellum concinnum MK098885 X _/99 Hydrophana fessula sp. nov. Viner 2021/289 X 1/100 Hydrophana sphaerospora MK098883 X Hydrophana trichiesiana sp. nov. Gruhn GUY18-573 X Mycostilla chromatica sp. nov. Spirin 14839 X Mycostilla vermiformis MG735417 X Endoperplexa dartmorica Spirin 11781 Protoacia reliqua sp. nov. Grootmyers 21072014 X Protoacia delicata ON117837 X Gelacantha pura MK098882 X Pseudohydnum gelatinosum ON117828 X 1/100;-— Protomerulius deceptorius SP. nov. Spirin 14811 X Protomerulius madidus MK484044 X 1/99 1/00 Protomerulius commotus MK484040 X 4/100 Protomerulius brachysporus Spirin 16288 X Protomerulius amiliavi sp. nov. Spirin 16165 X 4/100 Protomerulius dubius MK484041 X 4/100 4/100 Protomerulius minor MK484058 X Protomerulius pertusus MK484064 X 4/100 Protomerulius microsporus MK484055 X Protomerulius subreflexus MG757508 X Psilochaete multifora MK484066 Myxarium guianense sp. 1/100 1/100 0.99/90 Hyalodon piceicola MG735413 X nov. Gruhn GUY18-559 X P Myxarium cinnamomescens M Myxarium populinum KY801883 Myxarium fugacissimum MK098895 1/100 1/9 fyxarium podlachicum MK098914 X 0.9/ Myxarium minutissimum MK098904 X $ 1/96 Myxarium varium MK098919 X Myxarium simile MK098983 X 0.94/ Myxarium crozalsii MK098891 X = 1/100 - Myxarium mesomorphum MK098903 X 0.9/ Myxarium nucleatum KY801879 X i —= Myxarium grilletii MKO98896 X Myxarium frumentaceum MK098981 X Myxarium hyalinum KY801880 X Myxarium evanidum MK098894 X Myxarium spiniferum'sp. nov. MK098901 X Myxarium rotundum MK098982 X Myxarium crystallinum MKO098892 X 0.97/10, 1/100 Stypellopsis hyperborea MG857096 X Ofella glaira MK098920 X 1/100 Serendipita restingae MN595219 Serendipita herbamans KF061285 Serendipita vermifera DQ520096 Ditangium cerasi DQ520103 Sebacina incrustans DQ520095 wide 1/100 17400 Outgroup Exidiopsis gloeophora Jenni Norden 9609 0.08 Figure 1. Bayesian majority-rule consensus ITS + LSU-based tree of the Auriculariales overlaid with bootstrap support values from the maximum likelihood analysis. Support values are given as Bayesian posterior probabilities / ML bootstrap percentag- es. Species with stalked basidia are marked with a red X. | — Protohydnum clade; II — Elmerina clade; Ill - Hydrophana clade; IV — Endoperplexa — Mycostilla clade; V —- Protoacia —- Gelacantha clade; VI — Protomerulius clade; VIl - Myxarium clade. The Se- bacinales (Ditangium P. Karst., Sebacina, and Serendipita P. Roberts spp.) and Exidiopsis gloeophora were used as outgroups. Protohydnum nudum Ryvarden 9435 Protohydnum galzinii MG757511 0.99 Protohydnum galzinii Viner 2023/1023 0.99 Protohydnum galzinii CWU 4564 Protohydnum album Miettinen 19583 1 |“ Protohydnum album LE 23063 Protohydnum album LE 37320 Protohydnum pallidum Ryvarden 26180 0.97 Protohydnum elevatum LE F-347688 1 Protohydnum lactescens TAAM 192048 Protohydnum livescens Miettinen 15891.1 Og Protohydnum livescens Miettinen 20660 Protohydnum livescens Viner 2022/7 p24 Protohydnum livescens Miettinen 15872.2 Protohydnum livescens Miettinen 16000 { Protohydnum sp. Viasak 1808/145 Protohydnum cartilagineum MG735419 Basidiodendron glaucum MW259235 Basidiodendron trachysporum MW152419 Basidiodendron cf. trachysporum OL436974 0.09 Figure 2. Bayesian majority-rule consensus ITS-based tree of the Protohydnum clade. Support values are given as Bayesian posterior probabilities. Basidiodendron spp. were used as an outgroup. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 343 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 0.98 Protoacia crispans Viacheslav Spirin 17688 Protoacia reliqua Django Grootmyers 21072014 Protoacia delicata ON117837 Protoacia delicata Mk098922 Protoacia delicata MK098923 Protoacia delicata MK098921 Stypella sp. OR656496 Uncultured fungus KF222489 Gelacantha pura MK098882 Pseudohydnum gelatinosum HQ604801 0.03 Figure 3. Bayesian majority-rule consensus ITS-based tree of the Protoacia - Gelacantha clade. Support values are given as Bayesian posterior probabilities. Pseudohydnum gelatinosum (Scop.) P. Karst. was used as an outgroup. 0.99 MK484038 MX MK484035 SE 0.961_} Mk484033 FI MK484036 NO UDB05261178 CH OW844524 CN MK484037 RU-PRI Spirin 16288 FR DB05261390 EE 1 B0165096 EE UDB05261391 EE UGB 888803 f47 Ru-Bu MK484034 US-WA UDB03392882 US-OR 0.99 HM488454 US-OR -SSL kpag9s84 CA-BC UDB05261298 RO LR602625 CN 0.99 LR819392 CN UDB05261137 EE MT088178 CA-AB UDB05261780 EE Spirin 17127 FR HF675668 DE 0.97} UDB05261375 EE MK484040 NO UDB05262245 CZ Spirin 13617 CH UDB05261944 IT Psilochaete multifora MK484066 NO 0.05 MK484042 FI Viner 2019/154 FI 41 UDB0331509 EE UDB05260950 EE MK4i 0.99 UDB0133092 EE UDB05262185 BO MK484064 RU-NIZ 0.94} MK484062 RU-NIZ MK484063 NO Spirin 12743 RU-NIZ 0.97— MK484059 US-AR 0.95 FL kJ140733 US-WI MK484060 BR-PE Protomerulius sp. KY462616 AR 0.98" Protomerulius sp. UDB05261172 AR 1 0.99 Protomerulius b Protomerulius deceptor Protomerulius madidus Protomerulius commotus Protomerulius dubius Protomerulius pertusus Protomerulius minor Protomerulius microsporus MK484055 Mx. 1; Protomerulius subreflexus MK636543 ID Protomerulius subreflexus JX134481 CN Protomerulius substuppeus MK636540 UG Figure 4. Bayesian majority-rule consensus ITS-based tree of the Protomerulius clade. Support values are given as Bayesian posterior probabilities. Psilochaete multifora Spirin & Malysheva was used as an outgroup. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 344 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia 0.99 0.99 0.99 Myxarium cirratulum MK098979 4, Myxarium grilletii MKO98897 1 Myxarium grilletii Viacheslav Spirin 16479 Myxarium aff. grilletii MKO98896 1, Myxarium minutissimum MK098904 Myxarium minutissimum Viacheslav Spirin 17270 Myxarium fugacissimum MK098895 Myxarium podlachicum MK098914 Myxarium podlachicum Viacheslav Spirin 16589 Myxarium denticulatum Viacheslav Spirin 17365 Myxarium guianense Gerald Gruhn 18-559 1- Myxarium mesomorphum MK098903 Myxarium nucleatum KY801879 Myxarium simile MK098983 1- Myxarium varium MK098919 Myxarium varium Viacheslav Spirin 15646 0.95, Myxarium cinnamomescens MK098888 Myxarium cinnamomescens L@347687 Myxarium populinum KY801883 1 Myxarium frumentaceum Mk098981 1, Myxarium hyalinum KY801880 Myxarium hyalinum Viacheslav Spirin 17044 Myxarium legonii Viacheslav Spirin 16419 Myxarium aff. legonii MKO98900 0.99 Myxarium spiniferum MK098899 1 § Myxarium spiniferum MK098901 Myxarium evanidum Viacheslav Spirin 15193 1} Myxarium evanidum MK098894 Myxarium evanidum Viacheslav Spirin 17761 Myxarium evanidum MK098893 Myxarium mirabile MZ890593 Myxarium rotundum MK098982 Myxarium crystallinum llya Viner 2023_26 Myxarium crystallinum MK098892 0.2 Figure 5. Bayesian majority-rule consensus ITS-based tree of the Myxarium clade. Support values are given as Bayesian posterior probabilities. Myxarium crystallinum was used as an outgroup. sequence alignments — annotated with the number of taxa, characters, models of nucleotide evolution, and details of the corresponding MrBayes run — are available at https://doi.org/10.15156/BIO/3301247. The ITS-LSU dataset encompasses 65 species of the Auriculariales and six species as an outgroup (five members of the Sebacinales M. Weil, Selosse, Rexer, A. Urb. & Oberw., plus Exidiopsis gloeophora (Oberw.) Wojewoda as incertae sedis). The Auriculariales with stalked basidia are distributed among fifteen clades/sin- gle-species lineages. Of these, Elmerina Bres. (incl. Protodaedalea Imazeki), Prot- odontia Hohn., Myxariellum Spirin & Malysheva, Pseudohydnum, Hyalodon Maly- sheva & Spirin, Stypellopsis Spirin & Malysheva, and Ofella Spirin & Malysheva have been investigated in previous publications (Sotome et al. 2014; Malysheva et al. 2018; Spirin et al. 201 8a, 201 9a, b, c, 2023; Chen et al. 2020; Zhou et al. 2022, 2023; Coelho-Nascimento et al. 2024), while Tremiscus (Pers.) Lév. still awaits a proper revision. In the present study, we focus on the following clades in the tree (Fig. 1): 1. The Protohydnum clade (pp = 0.99, bs = 90%). As a monophyletic lineage, this group was first recognised by Weif§ and Oberwinkler (2001), who de- tected Bourdotia galzinii (Bres.) Torrend (the generic type of Bourdotia (Bres.) Bres. & Torrend), Ductifera pululahuana (Pat.) Donk (senior synonym of Ductifera millei Lloyd, the generic type of Ductifera Lloyd), and Ductifera sucina (Moller) K. Wells in a strongly supported clade. They stressed clear morphological similarities between Bourdotia and Ductifera (gelatinous MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 345 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia basidiocarps, presence of gloeocystidia) and suggested that they should be merged. Malysheva et al. (2018) found that the generic type of Proto- hydnum, P. cartilagineum Moller, is a member of the Bourdotia—Ductifera clade as well, which was again strongly supported. From a morphological perspective, including P. cartilagineum, an acystidiate, strongly hydnoid species, in one genus with Bourdotia and Ductifera appeared somewhat problematic. In the present study, we expand sampling of this clade with six additional species, of which four are newly described, one is reas- sessed (Exidiopsis livescens (Bres.) Bourdot & Maire) and given a new combination, and one is left unnamed due to the lack of fertile material. Our current data indicate that the presence of gloeocystidia cannot be considered a reliable character for the clade, as five of the ten species includ- ed in the ITS—LSU phylogeny lack them. These acystidiate species (includ- ing the type species of Protohydnum) cluster together (pp = 1, bs = 100%) and might be taxonomically interpreted as belonging to one well-defined ge- nus (i.e., Protohydnum s. str.). However, separating them from the rest of the taxa of the broader Protohydnum clade (i.e., Bourdotia and Ductifera spp.) would necessitate the introduction of three more genera, none of which would have distinct morphological differences. In particular, all species of Protohydnum s. str. possess stalked basidia with a stipe gradually widening towards the apical cells, the so-called petiolate basidia (cf. Wells and Raitviir 1975). Basidia of the same kind are characteristic of resupinate species in three other subclades of the Protohydnum clade, including Bourdotia galzinii (see Fig. 1), while species with cerebriform or cushion-shaped basidiocarps (Ductifera spp.) have sessile basidia (i.e., four-celled basidia devoid of a stalk). However, two of the three subclades contain both resupinate species with petiolate basidia and cerebriform species with sessile basidia, and it is therefore impossible to characterise them based on these traits. Other morphological characters (e.g., basidiospore shape and size) also do not provide significant grounds for defining these subclades. For this reason, we consider maintaining Protohydnum, Bourdotia, and Ductifera spp. in one genus as the most reasonable solution with our current knowledge of this group. A newly described P nudum is included in the ITS dataset (Fig. 2). Ad- ditionally, five more species are recombined below to Protohydnum based on morphological evidence following examination of their types. 2. The Elmericium lineage in the Elmerina clade (pp = 0.95, bs = 82%, Fig. 1) is represented by the single newly described species Elmericium alabas- trinum. Unlike other members of the clade, of which all but one are poroid, E. alabastrinum has corticioid, gelatinous basidiocarps. Morphologically and phylogenetically, we believe it is sufficiently distant from Elmerina and its relatives to warrant placement in a genus of its own. 3. The Hydrophana clade (pp = 1, bs = 100%, Fig. 1). The genus Hydrophana Malysheva & Spirin was recently introduced as a result of rearranging the Myxarium-like species, and it was, until now, limited to one species, Hy- drophana sphaerospora (Bourdot & Galzin) Malysheva & Spirin (Spirin et al. 2019b). In the present study, we add two new species to the genus, viz., Hydrophana fessula from northern Europe and Hydrophana trichiesiana from South America. We amend the generic description to encompass species with both ellipsoid and broadly cylindrical basidiospores. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 346 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 4. The Mycostilla clade (pp = 1, bs = 100%, Fig. 1). The genus Mycostilla Spirin & Malysheva was originally described as monotypic, with Mycos- tilla vermiformis (Berk. & Broome) Spirin & Malysheva as its only species (Spirin et al. 2019a). Here, we introduce a new species in the genus, My- costilla chromatica. M. chromatica is macroscopically quite different from M. vermiformis, and it lacks the cystidia that are characteristic of the latter species. We therefore amend the generic description of Mycostilla below. The two Mycostilla species were recovered as part of a larger, strongly supported clade that also includes the generic type of Endoperplexa P. Roberts, Endoperplexa dartmorica P. Roberts (pp = 1, bs = 100%, Fig. 1). At present, we refrain from merging these two genera, mainly because of the rather distinct morphology of E. dartmorica (species with constantly sessile basidia) and the notable phylogenetic distance between it and My- costilla spp. Other Endoperplexa species are not closely related to E. dart- morica and Mycostilla spp. (unpublished data). 5. The Gelacantha—Protoacia clade (pp = 0.95, bs = 97%, Fig. 1). The type species of two recently described genera, Gelacantha pura Malysheva & Spirin and Protoacia delicata Spirin & Malysheva, cluster together in the ITS-LSU tree, although the clade gains sufficient support only in the ML phylogeny. With our current knowledge of the group, we prefer to keep these genera separate due to differing basidiocarp morphology and high- ly divergent ITS sequences. A new species, Protoacia reliqua from North America, is introduced and assigned to Protoacia, primarily because of a higher morphological similarity with P delicata than with G. pura. However, its phylogenetic position could not be confidently resolved, as it is equally distant from the type species of both genera. One more new species, Pro- toacia crispans from Europe, is described as closely related to P reliqua, and a higher species diversity in this group is suggested based on envi- ronmental ITS sequences (Fig. 3). Nonetheless, any definitive conclusion about generic division in this clade (one large genus versus three genera — i.e., separate Gelacantha Malysheva & Spirin and Protoacia Spirin & Maly- sheva, plus a new genus for P reliqua and P. crispans) would be premature without broader taxon sampling and additional genetic markers. 6. The Protomerulius clade (pp = 1, bs = 100%, Fig. 1). In its current scope, Protomerulius Moller embraces mainly corticioid species formerly consid- ered members of Heterochaetella (Bourdot) Bourdot & Galzin, while po- roid genera originally assigned to the genus represent a minority (Spirin et al. 2019c). Here, we introduce two more corticioid species from Europe, Protomerulius amiliavi and Protomerulius deceptorius, and expand our cur- rent knowledge of Protomerulius species diversity and distribution using available environmental data (Fig. 4). 7. The Myxarium clade (pp = 1, bs = 100%, Fig. 1). The genus Myxarium Wallr. was recently reassessed through combined morphological and phyloge- netic evidence. It is recovered as a strongly supported clade in our ITS—LSU tree. Three new Myxarium species are described below, viz. Myxarium gul- anense (Fig. 1), Myxarium denticulatum, and Myxarium spiniferum (Fig. 5). The identity of M. legonii (P. Roberts) P. Roberts is reconsidered based on new morphological and DNA data, and Tremella inconspicua Pat. is formal- ly transferred to Myxarium based on a morphological study of its type. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 347 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Taxonomy Elmericium Spirin & V. Malysheva, gen. nov. MycoBank No: 858658 Etymology. Elmericium — derived from Elmerina, a phylogenetically close and ana- tomically similar genus, and Corticium, in reference to the crust-like basidiocarps. Description. Basidiocarps effused, smooth or nearly so, gelatinous, opal- escent or opaque, light-coloured, margin sharply delimited. Hyphal structure monomitic, hyphae hyaline or brownish, clamped. Cystidia present, hyaline, thin-walled, clavate to somewhat tapering. Hyphidia abundant, richly branched, forming a continuous layer. Basidia four-celled, longitudinally septate, ovoid-el- lipsoid to obconical, petiolate, embedded. Basidiospores smooth, thin-walled, broadly ellipsoid to ellipsoid. On dead wood of deciduous trees. Type species. E/mericium alabastrinum. Elmericium alabastrinum Spirin & V. Malysheva, sp. nov. MycoBank No: 858659 Figs 7A, 8A Holotype. Russia. Khabarovsk Reg.: Khabarovsk Dist., Hologu, Populus maximo- wiczii (partly corticated fallen log), 17.VIII.2012 Spirin 5311* (H, isotype — in LE). Etymology. Alabastrinus (Lat., adj.) — alabaster-like; in reference to the hy- menium colours. Description. Basidiocarps effused, up to 5 cm in widest dimension, smooth or indistinctly tuberculate, gelatinous, opalescent, greyish-white, often with red- dish-brown spots, 0.5-1 mm thick, in dry condition opaque, pinkish-grey or grey, with vinaceous-brown or brownish-black stains, crustose, margin sharply delimit- ed, usually slightly elevated, adnate or detaching, concolourous with hymenial sur- face. Hyphal structure monomitic, hyphae hyaline or brownish, clamped; subicu- lar hyphae thick-walled, subparallel, 3-5 um in diam., subhymenial hyphae thin- to slightly thick-walled, interwoven or ascending, densely arranged, 2—4 um in diam., with occasional inflations up to 6 um in diam. Cystidia abundant, hyaline, clavate to somewhat tapering, 20-30 x 5-8 um, slightly projecting. Hyphidia abundant, richly branched, 1-2 um in diam. at the apex, usually forming a continuous layer up to 15 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid to ob- conical, pedunculate (petiolate), (16—-) 17-27.5 (—30) x (9.8-) 10.1-14.0 (-14.3) um (n = 30/2), stalk up to 26 x 5-6 um, narrowing to the base, sterigmata tubular, gradually tapering, up to 23 x 3-4 um. Basidiospores smooth, thin-walled, broadly ellipsoid to ellipsoid, (8.0—) 8.6-12.2 (-12.3) x (5.7—) 5.9-8.1 (—8.2) um (n = 50/2), E=10:23-10:32;W = .7,03-7.20:0' = (1.2) 1.38=1:7 (=1.8),.0 = 1.43=1.48. Distribution and ecology. East Asia (Russian Far East); corticated logs or still-attached branches of deciduous trees (mostly Populus) along riversides. Remarks. At present, El/mericium alabastrinum is the single known corticioid representative of the E/merina clade in the Auriculariaceae Fr. ex Lindau. All oth- er members of this group (Aporpium Bondartsev & Singer ex Singer, Elmerina, and Protodaedalea) are poroid except Elmerina sclerodontia (Mont. & Berk.) Miettinen & Spirin, which has clavarioid basidiocarps (see Malysheva et al. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 348 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 2018). Elmericium alabastrinum has petiolate basidia nearly identical in shape and size to those of Elmerina and Protodaedalea. However, the rest of the mac- roscopic traits (smooth, crust-like, gelatinous basidiocarps vs. poroid, cartilag- ineous, or leathery ones) and anatomical features (hyphal structure, hymenial construction, and basidiospore shape) clearly separate Elmericium from its rel- atives. The freshly collected basidiocarps of E. alabastrinum are usually sterile, although they start active sporulation after being rehydrated for several hours. Hydrophana V. Malysheva & Spirin, Nordic Journal of Botany 37 (e02394): 8, 2019, emend. Description. Basidiocarps effused, continuous, smooth or tuberculate, gelati- nous, thin. Hyphal structure monomitic; hyphae clamped. Cystidia absent; hy- phidia present, richly branched, 0.5-1.5 um in diam. Basidia four-celled, longi- tudinally septate, broadly ellipsoid to globose, pedunculate (stalk occasionally reduced). Basidiospores hyaline, thin-walled, broadly cylindrical or broadly ellip- soid to globose. On rotten wood. Type species. Sebacina sphaerospora Bourdot & Galzin. Originally, Hydrophana was introduced to encompass one species, H. sphaerospora (Bourdot & Galzin) Malysheva & Spirin (formerly Myxari- um sphaerosporum (Bourdot & Galzin) D.A. Reid), which turned out to be not closely related to the rest of the Myxarium-like taxa. Morphologically, Hydrophana was distinguished from Myxarium s. lato mainly due to broad- ly ellipsoid or subglobose basidiospores in the type species (Spirin et al. 2019b). However, adding two new Hydrophana species with broadly cylin- drical or ellipsoid basidiospores necessitates a redefinition of the genus. In its current scope, Hydrophana can be separated from the ellipsoid-spored Myxarium spp. due to continuous (not reticulate or pustulate-coalescing) basidiocarps, smooth (or nearly so) hymenophore, narrower hyphidia, and slenderer sterigmata. The two latter features can be used for distinguish- ing Hydrophana spp. from Ofella glaira (Lloyd) Spirin & Malysheva. In turn, Myxariellum spp. have well-differentiated tapering cystidia, and their basidia possess a thicker stalk and wider sterigmata than do Hydrophana. Hydrophana fessula Viner & Spirin, sp. nov. MycoBank No: 858660 Fig. 8B Holotype. Finland. Uusimaa: Helsinki, Talosaari, Picea abies (fallen decorticat- ed log), 13.X.2021 Viner 2021/289% (H 6112924). Etymology. Fessulus (Lat., adj.) — limp; in reference to quickly collapsing hyphae. Description. Basidiocarps effused, up to 4 cm in widest dimension, smooth or tuberculate, gelatinous, semitranslucent, greyish, 0.4-0.7 mm thick, in dry condi- tion vernicose, hardly visible, margin gradually thinning-out. Hyphal structure mo- nomitic, hyphae hyaline, clamped; subicular hyphae with a distinct wall, interwoven, 2-4 um in diam., subhymenial hyphae thin-walled, quickly collapsing, ascending or interwoven, 2-3 um in diam. Cystidia absent. Hyphidia abundant, richly branched, MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 349 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 0.5-1 um in diam. at the apex, partly covering hymenial cells. Basidia four-celled, longitudinally septate, broadly ellipsoid to globose, pedunculate, (8.7—) 8.8-10.2 (-10.8) x (7.2—) 7.3-8.7 (—9.0) pm (n = 20/1), stalk distinct, up to 30 x 1.5-2.5 pm, sterigmata gradually tapering, occasionally bifurcate, up to 25 x 1.8-2.2 um. Ba- sidiospores smooth, thin-walled, broadly cylindrical to broadly ellipsoid, more rarely lacrymoid or ovoid, (5.2—) 5.3-7.2 x (3.8—-) 4.0-5.2 (—5.4) um (n = 30/1), L = 6.31, W = 4.58, Q’ = (1.2-) 1.3-1.6 (-1.7), Q = 1.39, often with a large central oil drop. Distribution and ecology. Europe (Finland); decorticated coniferous logs (Picea). Remarks. Hydrophana fessula is described here as the second European representative of the genus. It differs from H. sphaerospora mainly in having broadly cylindrical/ellipsoid basidiospores (broadly ellipsoid to nearly globose in the latter species). Moreover, H. fessula was found on coniferous wood, while H. sphaerospora seems to be restricted to deciduous trees. Ofella glaira, also inhabiting coniferous hosts, can easily be mistaken for H. fessula. However, it has thinner basidiocarps as well as wider hyphidia and sterigmata, and it occa- sionally produces hymenial cystidia. Basidiospores of O. glaira are more regular in shape than in H. fessula, varying from ellipsoid to subglobose (see descrip- tion in Spirin et al. 2019b). Both species seem to be very rare. While H. fessula is currently known from the type locality only, O. glaira has been detected a few times in Estonia, Finland, Norway, and Sweden (the /ocus classicus). Addition- ally, the GenBank sequence HQ441914 of an uncultured fungus isolate from Finland (Rajala et al. 2011) belongs to O. glaira. Hydrophana trichiesiana Gruhn & Rodel, sp. nov. MycoBank No: 858661 Figs 6A, 7B, 8C Holotype. French Guiana. Régina: Noruragues, Saut Pararé, rotten wood of an- giosperm, 4.XII.2018 Gruhn GUY18-573*% (LIP, isotype — H). Etymology. Trichiesianus (Lat., adj.) — in homage to Gérard Trichies, a fa- mous discoverer of minuscule heterobasidiomycetes. Description. Basidiocarps effused, up to 3 cm in widest dimension, tu- berculate, gelatinous, opalescent, cream-coloured to pale ochraceous, 0.2- 0.3 mm thick, in dry condition ochraceous-brown, vernicose, margin gradually thinning-out. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hyphae thin-walled, interwoven or subparallel, 2-3 um in diam., subhymenial hyphae very thin-walled, quickly collapsing, interwoven, rather densely arranged and partly glued together, 1-2 (—2.5) um in diam. Cystidia absent. Hyphidia abundant, richly branched, 0.8-1.2 um in diam. at the apex, partly covering hy- menial cells. Basidia four-celled, longitudinally septate, broadly ellipsoid to glo- bose, sessile or pedunculate, (8.0—) 8.2—-9.8 (-10.1) x (7.4-) 7.8-8.8 (—9.0) um (n = 20/1), stalk usually strongly reduced, up to 3 x 2 um, sterigmata gradually tapering, up to 18 x 1.5-2 um. Basidiospores smooth, thin-walled, ellipsoid to broadly ellipsoid, the longest spores broadly cylindrical and sometimes slightly curved, (5.1—) 5.2-7.0 (—7.2) x (3.7—) 3.8-4.7 (-—4.8) um (n = 30/1), L = 6.08, W = 4.21, Q’ = (1.2-) 1.3-1.7 (-1.8), Q = 1.45, often with a large central oil drop. Distribution and ecology. South America (French Guiana); decorticated, de- cayed angiosperm wood. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 350 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Figure 6. Basidiocarps of: A. Hydrophana trichiesiana (holotype); B. Mycostilla chromatica (holotype); C. Myxarium gui- anense (holotype); D. Protoacia reliqua (holotype); E. Protohydnum erumpens (holotype); F. P. livescens (specimen Spirin 15619); G. Protomerulius amiliavi (holotype); H. P deceptorius (specimen Spirin 16784). Scale bar: 1 cm. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 35] Viacheslav Spirin et al.: Auriculariales with pedunculate basidia Figure 7. Microscopic structures of: A. Elmericium alabastrinum (holotype) (1 — hymenial cells and subhymenial hy- phae; 2 — subicular hyphae); B. Hydrophana trichiesiana (holotype); C. Protohydnum album (specimen Miettinen 196583); D. P. galzinii (specimen Miettinen 15900.4). Scale bar: 10 um. Remarks. Hydrophana trichiesiana is described here as the first represen- tative of the genus found in the tropics. It differs from the two other species of the genus, H. fessula and H. sphaerospora, in having basidia with a strongly reduced, although still detectable, stalk. Basidiospores of H. trichiesiana are similar to those of H. fessula, although slightly narrower on average. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 359 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia W O S .Od0G .oGoda Figure 8. Basidiospores of: A. Elmericium alabastrinum (holotype); B. Hydrophana fessula (holotype); C. H. trichiesiana (holotype); D. Mycostilla chromatica (holotype); E. M. guianense (holotype); F. M. inconspicuum (holotype); G. Protoacia crispans (holotype); H. P. reliqua (holotype). Scale bar: 10 um. Mycostilla Spirin & V. Malysheva, Antonie van Leeuwenhoek 112: 760, 2018, emend. Description. Basidiocarps appearing as small gelatinous outgrowths on a hard- ly visible joint subiculum, later fusing into reticulate or continuous compound fructifications. Hyphal structure monomitic, hyphae clamped. Tramal cystidia tubular, slightly tapering upwards, apically blunt, or absent. Gloeocystidia (if present) running more or less parallel to tramal cystidia. Basidia two — four- celled, pedunculate, with slender, distantly located sterigmata. Basidiospores thin-walled, subglobose, repetitive, often with one large oil drop. Type species. Dacrymyces vermiformis Berk. & Broome. The generic description of Mycostilla is amended here to encompass a new species, M. chromatica. In contrast to the generic type, M. vermiformis, it has continuous (not reticulate) basidiocarps and lacks cystidia. Nevertheless, it is phylogenetically quite close to M. vermiformis and is therefore described as a Mycostilla. Basidia of both species are of the same shape (slightly larger in M. chromatica than in M. vermiformis), and basidiospores are nearly identical. Mycostilla chromatica Spirin & Grebenc, sp. nov. MycoBank No: 858662 Figs 6B, 8D Holotype. Slovenia. Kocevje: Podstenice, Rajhenavski Rog, Abies alba (fallen decorticated log), 21.VIII.2021 Spirin 14839* (H, isotype — LJF). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 353 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Etymology. Chromaticus (Lat., adj.) -— chrome-yellow, in reference to the ba- sidiocarp’s colour. Description. Basidiocarps effused, first small, then fusing together and reaching up to 20 cm in longest dimension, indistinctly or clearly tuberculate, gelatinous, semitranslucent, containing numerous chrome-yellow grains, 0.1-0.4 mm thick, drying to a bright-yellow thin crust, margin gradually thinning out. Hyphal structure monomitic, hyphae hyaline, clamped, richly encrusted by chrome-yellow angular crystals occasionally fusing together in large amorphous concretions; subicular hyphae thin-walled or with a distinct wall, interwoven, anastomosing, 2-4 ym in diam. (occasionally inflated up to 6 um in diam.), subhymenial hyphae thin-walled, quickly collapsing, interwoven, 2-3 um in diam. Cystidia absent. Hyphidia scat- tered, simple or sparsely branched, 1-1.5 um in diam. at the apex. Basidia four- celled, longitudinally septate, broadly ellipsoid to globose, pedunculate, (8.3—) 8.7— 11.0 (-11.2) x (7.8-) 8.0-9.0 (—9.2) um (n = 20/2), stalk usually distinct, up to 15 x 2-3 um, sterigmata gradually tapering, up to 20 x 1.5—2 um. Basidiospores smooth, thin-walled, ellipsoid to broadly ellipsoid or subglobose, more rarely globose, (4.2—) 4.7-6.1 (-6.2) x (3.6—-) 3.8-5.2 (—5.4) um (n = 60/2), L = 5.20-5.31, W = 4.46- 4.78, Q’ = (1.0-) 1.1-1.3 (-1.4), Q = 1.09-1.20, often with a large central oil drop. Distribution and ecology. Europe (Slovenia); fallen decorticated logs of co- nifers (Abies). Remarks. Mycostilla chromatica is a distinctive species due to its brightly co- loured, effused, and gelatinous basidiocarps. It has been found twice in the pristine fir-beech forests of Slovenia. The colours of M. chromatica are strongly reminis- cent of the corticioid fungus Flavophlebia sulfureoisabellina (Litsch.) K.H. Larss. & Hjortstam (Agaricales Underw., Basidiomycota). The latter species also occurs on Abies alba logs in old-growth forests of Central Europe. However, it has thicker basidiocarps than M. chromatica and is microscopically completely different. Myxarium Wallr., Flora Cryptogamica Germaniae 2: 260, 1833. Note. For a modern description of the genus, see Spirin et al. (2019b). Type species. Myxarium nucleatum Wallr. Myxarium denticulatum Spirin, sp. nov. MycoBank No: 858663 Fig. 9C Holotype. Sweden. Bohuslan: H6n6, Ersdalsvagen, Sorbus sp. (recently fallen corticated branch), 12.VIII.2024 Spirin 17365* (GB, isotype — H). Etymology. Denticulatus (Lat., adj.) - possessing small teeth. Description. Basidiocarps effused, small and inconspicuous, up to 8 mm in widest dimension, semitranslucent, gelatinous, greyish, adnate, almost invis- ible in dry condition; hymenophore hydnoid, spines rather regularly arranged, acute, single, up to 0.1 mm long, 5-6 per mm; subiculum watery greyish, semitranslucent, 0.02-0.03 mm thick; margin gradually thinning-out. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hyphae thin-walled, subparallel, hardly discernible, 1-2 um in diam., subhymenial hyphae ascending MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 354 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia e JQO00dE OG »UG0dG Figure 9. Microscopic structures of the Myxarium legonii complex: A. Myxarium legonii (specimen Spirin 16419) (hymenial cells and subhymenial hyphae); B. M. legonii (specimen Spirin 16419) (crystals); C. M. denticulatum (holotype) (basidiospores); D. M. legonii (specimen TAAM 132119) (basidiospores); E. M. spiniferum (holotype) (basidiospores). Scale bar: 10 um. or interwoven, thin-walled, and quickly collapsing, (1.0-) 1.1-2.5 (-—2.6) um in diam. (n = 20/1). Crystals absent. Hyphidia abundant, richly branched, 1-1.5 um in diam. in the apical part, distributed among basidia and partly cov- ering basidial cells. Basidia two — four-celled, longitudinally septate, broadly ellipsoid to subglobose, pedunculate, (6.5—) 7.0-8.6 (-8.9) x (5.8-) 6.0-7.5 (-7.8) um (n = 20/1), scattered, stalk up to 15 x 1.5—2 um, sterigmata up to 10 x 2-2.2 um, sometimes bifurcate. Basidiospores narrowly ellipsoid to broadly cy- lindrical, occasionally slightly concave on the ventral side, (5.0—) 5.1-7.0 (-7.3) x 3.0-4.2 (—4.8) um (n = 33/1), L = 6.18, W = 3.57, Q’ = (1.2-) 1.4-2.0 (-2.1), Q = 1.75, usually with a large central oil drop. Distribution and ecology. Europe (Sweden); fallen angiosperm branches (Sorbus). Remarks. Myxarium denticulatum produces extremely thin basidiocarps bearing tiny spines, which are detectable only under magnification. Due to its regularly hydnoid hymenophore, it can be confused with M. legonii. However, the latter species bears more pronounced spines and has on average narrow- er basidiospores (see description below). Another similar species, Myxarium MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 355 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia evanidum Spirin & K.H. Larss., possesses irregularly arranged spine-like out- growths on the hymenial surface. These outgrowths disappear completely after drying in M. evanidum; in contrast, spines of M. denticulatum are visible even in dried material. Under the microscope, M. denticulatum and M. evanidum are almost indistinguishable. Phylogenetically, M. denticulatum, M. evanidum, and M. legonii are not closely related (Fig. 5). Myxarium denticulatum is current- ly known only from the type locality, but it is presumably overlooked elsewhere due to its highly diminutive basidiocarps. Myxarium guianense Gruhn & Spirin, sp. nov. MycoBank No: 858664 Figs 6C, 8E Holotype. French Guiana. Régina: Noruragues, Saut Pararé, decorticated log on the ground, 3.XII.2018 Gruhn GUY18-559* (LIP. isotype — H). Etymology. Guianensis (Lat., adj.) — originating from French Guiana. Description. Basidiocarps first appearing as small pustules, 0.03-0.05 mm in diam., then fusing together and forming a compound basidiocarp, up to 3 cm in widest dimension, indistinctly tuberculate, gelatinous, opalescent, greyish, 0.1-0.2 mm thick, in dry condition vernicose, hardly visible, mar- gin sharply delimited, adnate. Hyphal structure monomitic, hyphae hyaline, clamped, frequently anastomosing; subicular hyphae with a distinct wall, interwoven or subparallel, 1.5—5 (6) um in diam., often slightly inflated at septa, subhymenial hyphae thin-walled or with a distinct wall, tightly glued together, ascending or interwoven, 1-4 um in diam. Cystidia rare, distinctly tapering to almost subulate, 16-26 x 5.0-8.4 um (n = 5/1), projecting up to 15 um above hymenial layer. Hyphidia richly branched, 1-1.5 um in diam. at the apical part, scattered among basidia. Basidia four-celled, longitudinal- ly septate, ellipsoid to broadly ellipsoid, pedunculate, (7.7—) 7.8-9.4 (-9.7) x (6.5—-) 6.6-7.2 (—7.3) um (n = 20/1), stalk distinct although sometimes strongly reduced, up to 10 x 2-2.5 um, sterigmata gradually tapering, rarely bifurcate, up to 10 x 1.2-1.5 um. Basidiospores smooth, thin-walled, nar- rowly ellipsoid to cylindrical, the longest spores often slightly curved, (5.4—) 5:6-7.3 (-7.8)-* (3:0-).3.1-4:1 (-4,4) pm (n = 3671),\L = 6.65, W= 3; 71, Q’ = (1.4-) 1.5-2.1 (—2.3), Q = 1.80. Distribution and ecology. South America (French Guiana); decorticated an- giosperm wood. Remarks. Morphologically, M. guianense is most similar to the Europe- an Myxarium minutissimum (Hohn.) Spirin & Trichies. However, the initially pustulate basidiocarps of M. guianensis fuse together completely and pro- duce a crustaceous continuous one, while in M. minutissimum they fuse only partly, and therefore the compound basidiocarps have a very character- istic reticulate shape. Moreover, M. guianense differs from M. minutissimum in having cystidia. Phylogenetically, these species are not closely related (Figs 1, 5). Differences between M. guianense and M. inconspicuum are dis- cussed under the latter species. Myxarium guianense is so far known from the type locality in French Guiana. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 356 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia Myxarium inconspicuum (Pat.) Spirin, comb. nov. MycoBank No: 858675 Fig. 8F = Tremella inconspicua Pat., Bulletin de la Société Mycologique de France 9: 138, 1893. Holotype. Ecuador. Pichincha: Quito (surroundings), dead wood, Il.1892 Lagerheim (FH00060386, studied). Description. Basidiocarps first pustular, 0.2-0.4 mm in diam., then fusing to- gether and forming a compound basidiocarp, up to 5 mm in widest dimension, indistinctly tuberculate, gelatinous, opalescent, whitish, 0.1-0.2 mm thick, in dry condition hardly visible, margin sharply delimited, adnate. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hyphae totally collapsed, subhy- menial hyphae thin-walled, ascending, 1.5-2.5 um in diam. Hyphidia abundant, richly branched, 1-2 um in diam. at the apical part, scattered among basidia and partly covering basidial cells. Basidia four-celled, longitudinally septate, el- lipsoid to broadly ellipsoid, pedunculate, (8.1-) 8.3-9.2 (-10.6) x (6.2—-) 6.5- 8.2 (-8.6) um (n = 20/1), stalk up to 15 x 2—2.5 pm, sterigmata up to 7 x 1.5 um. Basidiospores smooth, thin-walled, narrowly ellipsoid to ellipsoid or more rarely cylindrical, (5.0—) 5.7-8.2 (—8.9) x (3.4—) 3.6-5.0 (—5.1) um (n = 30/1), L = 6.99, W = 4.30, Q’ = (1.3-) 1.4-2.0 (—2.2), Q = 1.63. Remarks. Tremella inconspicua was described from Ecuador (Patouillard and Lagerheim 1893), and its connection with Myxarium was discussed by Spirin et al. (2019b). We restudied the type specimen of T. inconspicua and are fairly confident that it belongs to Myxarium. Both macroscopically and anatomically, M. inconspicuum is similar to the European Myxarium grilletii (Boud.) D.A. Reid; it differs from the latter species in having predominantly narrowly ellipsoid spores with a convex ventral side, while in M. grilletii (European specimens) the spores are mainly cylindrical or broadly cylindrical and often somewhat curved. However, the North American specimens of M. grilletii studied and illustrated by Spirin et al. (2019b) possess predominantly ellipsoid basidiospores. An ITS sequence ob- tained from the Canadian specimen of M. grilletii (GenBank MK098896, designat- ed as Myxarium aff. grilletii in Fig. 5) is identical with an unnamed sequence from the USA (GenBank KX193945), and they clearly deviate from M. grilletii sequenc- es from Europe. They may therefore represent a separate species and may in fact be conspecific with M. inconspicuum. Answering this question is not feasible without access to newly collected and sequenced material from Ecuador. Myxar- ium guianense introduced above differs from M. inconspicuum by its smaller dis- crete basidiocarps, slightly narrower basidiospores, and the presence of cystidia. Myxarium legonii (P. Roberts) P. Roberts, Nordic Journal of Botany 37 (e02394): 15, 2019. Fig. 9A, B, D = Stypella legonii P. Roberts, Mycotaxon 69: 228, 1998. Holotype. United King- dom. England: Surrey, Runnymede, Cooper's Hill, U/mus sp., 5.1II.1988 Legon (K(M) 49367). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 357 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Description. Basidiocarps effused, covering a few mm, semitranslucent, gelat- inous, whitish or greyish, adnate; hymenophore hydnoid, spines regularly ar- ranged, acute, single or fasciculate, 0.1-0.5 mm long, 5-7 per mm; subiculum first watery greyish, semitranslucent, then whitish, opaque, sometimes shin- ing, 0.02-0.05 mm thick; margin gradually thinning-out. Hyphal structure mo- nomitic, hyphae hyaline, clamped; subicular hyphae thin-walled, predominantly subparallel, 1-3 um in diam., tramal hyphae subparallel, subhymenial hyphae ascending, very thin-walled, and quickly collapsing, (1.2—) 1.6-2.6 (-3.2) um in diam. (n = 60/3). Acicular crystals abundant among hyphal tissues, often aggregated in large groups up to 20 um in the widest dimension. Hyphidia abundant, simple to branched, 1-1.5 um in diam. at the apical part, distribut- ed among basidia. Basidia four-celled, longitudinally septate, broadly ellipsoid to subglobose, pedunculate, (6.7—) 6.8-9.5 (—9.8) x (5.3—-) 5.8-7.3 (-7.4) um (n = 32/3), scattered, stalk up to 12 x 2—2.5 um, sterigmata up to 7 x 1.5-2 um. Basidiospores cylindrical to broadly cylindrical, often slightly curved, (4.6—) 4.9-7.6 (-8.2) x (2.6—-) 2.7-4.0 (—4.4) um (n = 90/3), L = 5.50-6.28, W = 3.29- 8:35; =(104 =). 1,.5=223(5256),.Q-="1.685 1:89; Distribution and ecology. Europe (France, Spain, United Kingdom); strongly decomposed wood of angiosperms. Remarks. Originally described as a member of Stypella Moller (Roberts 1998), the species was recently moved to Myxarium (Spirin et al. 2019b). The species was, however, accepted as a species complex because available ITS sequences showed clear differences between the European and North Ameri- can specimens. In the present study, the latter are excluded from our concept of M. legonii and assigned to M. spiniferum, described below. Here we reassess M. legonii based on newly collected specimens from the western part of Europe, as well as a specimen collected in the Jocus classicus. We found the latter (TAAM 132119) to be morphologically iden- tical to three recent specimens from France and Spain, of which one was sequenced. These all have considerably larger basidiospores than indicated in the protologue (where they were presumably measured from a spore print) and possess abundant acicular crystals in all parts of the basidiocarps (Fig. 9). Phylogenetic analysis shows that the specimen Spirin 9511, treated as M. legonii in our earlier study (Spirin et al. 2019b), is not conspecific with the rest of the European collections. This specimen from the European part of Russia has smaller basidia and shorter basidiospores than other European specimens of M. legonii, and it lacks crystals. However, all these differences may be age-dependent, and we are therefore unwilling to introduce a new species for this specimen without additional sampling. Myxarium legonii was also reported from Malawi (Spirin et al. 2019b). The identity of this ma- terial should be clarified with more specimens from southern Africa. Myxarium spiniferum Spirin & V. Malysheva, sp. nov. MycoBank No: 858665 Fig. 9E Holotype. Canada. Alberta: Edmonton, Louise McKinney Riverfront Park, Pop- ulus alba (rotten decorticated log), 28.VII.2015 Spirin 8986% (H, isotype — LE). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 358 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Etymology. Spiniferum (Lat., adj.) — bearing spines. Description. Basidiocarps effused, up to 3 cm in widest dimension, semi- translucent, gelatinous, whitish or greyish, adnate; hymenophore hydnoid, spines regularly arranged, acute, single or fasciculate, 0.1-0.6 mm long, 5-7 per mm; subiculum first watery greyish, semitranslucent, then whitish, opaque, 0.02-0.05 mm thick; margin gradually thinning-out. Hyphal structure monomit- ic, hyphae hyaline, clamped; subicular hyphae thin-walled, predominantly sub- parallel, 1-2 um in diam., tramal hyphae subparallel, subhymenial hyphae as- cending, very thin-walled, and quickly collapsing, (1.6-) 1.9-3.0 (-3.1) um in diam. (n = 20/1). Acicular crystals quite rare, spread among hyphal tissues, often aggregated in large groups up to 20 um in the widest dimension. Hyph- idia occasionally present, simple to sparsely branched, 1-1.5 um in diam. at the apical part, distributed among basidia. Basidia four-celled, longitudinally septate, broadly ellipsoid to subglobose, pedunculate, (6.0—) 6.8-8.8 (—9.2) x (5.3-) 5.8-6.9 (—7.0) um (n = 20/1), partly glued together and often forming a continuous layer, stalk up to 8 x 2 um, sterigmata up to 10 x 1.8-2.5 um. Basid- iospores cylindrical to broadly cylindrical, occasionally slightly curved, (4.1-) 4.3-5.8 (—5.9) x (2.3—-) 2.5-3.7 (—3.8) um (n = 90/3), L = 5.19-5.27, W = 2.98- 3.13; 0 =(14-)1.5-271.(-2.2),,O'=1.7051.75. Distribution and ecology. North America (Canada — Alberta, USA —- New York, Tennessee); strongly decomposed wood of angiosperms. Remarks. Myxarium spiniferum is described here as the North American sibling species of M. legonii. Morphologically, it differs from the latter species in having smaller basidiospores. The photograph of M. /egonii in Spirin et al. (2019b) belongs to M. spiniferum. Protoacia Spirin & V. Malysheva, Nordic Journal of Botany 37 (e02394): 19, 2019. Note. For the genus description, see Spirin et al. (2019b). Type species. Protoacia delicata Spirin & V. Malysheva. The generic type of Protoacia, P. delicata, possesses broadly ellipsoid or sub- globose basidiospores. Here we add two new species with ellipsoid to cylindri- cal basidiospores to Protoacia. However, we do not amend the generic descrip- tion of Protoacia due to the somewhat uncertain status of the genus versus Gelacantha (see Results). The single species of that genus, G. pura, differs from the three Protoacia species in having more robust basidiocarps with irregularly distributed and partly fusing spines, as well as wider subicular hyphae and hy- phidia. At least one more undescribed species closely related to P delicata can be recognised based on available sequences in GenBank (Fig. 3). Protoacia crispans Spirin, sp. nov. MycoBank No: 858666 Fig. 8G Holotype. Sweden. Halland: Sar6é, Sar6 Vasterskog, Pinus sylvestris (strongly decayed log with a brown rot), 12.X.2024 Spirin 17688* (GB, isotype — H). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 359 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Etymology. Crispans (Lat., present participle of ‘crispo’) — trembling, in refer- ence to delicate consistence of basidiocarps. Description. Basidiocarps effused, up to 2 cm in widest dimension, semi- translucent, gelatinous, whitish, adnate; hymenophore hydnoid, spines acute, single, 0.1-0.3 mm long, 6-7 per mm; subiculum hardly visible, semitranslu- cent, 0.02—0.05 mm thick; margin gradually thinning-out. Hyphal structure mo- nomitic, hyphae hyaline, clamped, frequently anastomosing; subicular hyphae thin- to slightly thick-walled, interwoven, 1-3 um in diam., subhymenial hyphae thin-walled, quickly collapsing, interwoven, 1-3 um in diam. Cystidia absent. Hyphidia abundant, richly branched, 1-2 um in diam. at the apex, scattered among basidia or partly covering basidial cells. Basidia (two-) four-celled, longitudinally or obliquely septate, broadly ellipsoid to globose, pedunculate, (9.0-) 9.2-11.9 (-12.0) x (7.2-) 7.3-9.1 (-9.2) um (n = 20/1), stalk distinct, up to 20 x 2-3.5 um, sterigmata gradually tapering, rarely bifurcate, up to 15 x 2-3 um. Basidiospores smooth, thin-walled, narrowly ellipsoid or broadly cylin- drical (shorter spores) to cylindrical-subfusiform or somewhat rhomboid (lon- ger spores), more rarely almost pyriform or lacrymoid, (5.2—) 5.9-9.3 (-10.2) x (3.3-) 3.5-5.4 (-5.8) um (n = 30/1), L = 7.48, W = 4.61, Q’ = (1.3-) 1.4-2.1 (—2.2), Q = 1.64, with a large central oil drop. Distribution and ecology. Europe (Sweden); very rotten coniferous logs (Pinus). Remarks. Protoacia crispans is morphologically highly similar to P. delicata. The two species differ mainly in basidiospore morphology, regularly broadly ellipsoid or subglobose in P delicata and highly diverse, varying from narrowly ellipsoid or broadly cylindrical to subfusiform or lacrymoid in P. crispans. More- over, P. crispans has shorter spines than P. delicata, which are hardly detectable by the naked eye. Phylogenetically, P crispans is much closer to P. reliqua than to P. delicata; their differences are listed under the latter species. Protodontia subgelatinosa (P. Karst.) Pilat is another species that could be mistaken for P. crispans. In addition to different substrate preferences (angio- sperm wood versus conifer wood), P. subgelatinosa has wider hyphidia and more regularly shaped, ellipsoid, or ovoid (very rarely cylindrical) basidiospores (see description in Spirin et al. 2019b). Moreover, the spines of P subgelatinosa tend to fuse in groups of three — four, and no such pattern was observed in P crispans. Protoacia reliqua Grootmyers & Spirin, sp. nov. MycoBank No: 858667 Figs 6D, 8H Holotype. USA. Tennessee: Anderson Co., Norris, Norris Dam State Park, Junipe- rus virginiana (fallen decorticated log), 20.VII.2021 Grootmyers 2107201 4* (H). Etymology. Reliquus (Lat., adj.) - remaining, another one. Description. Basidiocarps effused, covering a few cm, semitranslucent, gelatinous, whitish, adnate; hymenophore hydnoid, spines acute, single, 0.05-0.1 mm long, 6-8 per mm; subiculum hardly visible, semitranslucent, 0.02-0.05 mm thick; margin gradually thinning-out. Hyphal structure monomit- ic, hyphae hyaline, clamped, frequently anastomosing; subicular hyphae thin- walled or with a distinct wall, interwoven, 2.5-4 um in diam., subhymenial hy- phae very thin-walled, quickly collapsing, interwoven, 2-3 um in diam. Cystidia MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 360 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia absent. Hyphidia abundant, richly branched, 1-1.5 um in diam. at the apex, scattered among basidia. Basidia four-celled, longitudinally septate, broad- ly ellipsoid to globose, pedunculate, (7.2—) 7.6—-9.6 (—10.2) x (5.6-) 6.0-7.3 (-7.5) um (n = 20/1), stalk distinct, up to 25 x 2-2.5 um, sterigmata gradually tapering, up to 22 x 2—2.5 um. Basidiospores smooth, thin-walled, narrowly el- lipsoid or ovoid to broadly cylindrical, (5.1-) 5.2-7.7 (-8.1) x (3.2-) 3.3-4.5 (-4.8) um (n = 31/1), L = 6.20, W = 3.89, Q’ = (1.2—) 1.3-1.8 (-1.9), Q = 1.60, with a large central oil drop. Distribution and ecology. North America (USA — Tennessee); rotten conifer- ous logs (Juniperus spp.). Remarks. Protoacia reliqua is a North American relative of P crispans. It dif- fers from the latter species in having shorter spines, as well as smaller basidia and basidiospores. The basidiospores of P reliqua are not as variable in shape as those of P crispans, varying from ellipsoid-ovoid to broadly cylindrical. The species is so far known only from the type locality but is likely overlooked due to its diminutive basidiocarps. Protohydnum Moller, Botanische Mittheilungen aus den Tropen 8: 173, 1895, emend. = Bourdotia (Bres.) Bres. & Torrend, Brotéria Serie Botanica 11: 88, 1913. Type species. Sebacina galzinii Bres. (selected by Clements and Shear 1931: 342). = Ductifera Lloyd, Mycological Writings 5: 711, 1917. Type species. Ductifera millei Lloyd. = Gloeotromera Ervin, Mycologia 48: 692, 1956. Type species. Exidiopsis alba Lloyd. Description. Basidiocarps cushion-shaped — cerebriform or completely resupinate, with adnate or elevated margin, gelatinous; hymenial surface nearly smooth or (in one species) distinctly hydnoid. Hyphal structure monomitic, hyphae clamped. Gloeocystidia present in most species, tubular, variably tapering upwards, usually embedded. Basidia strictly four-celled, sessile (cerebriform species) or predom- inantly pedunculate to petiolate (resupinate species), with rather thick, distinctly located sterigmata. Basidiospores thin-walled, cylindrical to ellipsoid, more rarely cylindrical-subfusiform or broadly ellipsoid — subglobose, repetitive. Type species. Protohydnum cartilagineum Moller. Here we redefine Protohydnum and merge it with Ductifera and Bourdotia. Additionally, two species earlier included in Exidiopsis (Bref.) Mdller s. lato (i.e., Exidiopsis glabra Moller and E. livescens) are also reclassified into Protohyd- num. In its current scope, the genus contains sixteen species. Phylogenetically, the large Protohydnum clade is the sister lineage of Ba- sidiodendron Rick (Wei and Oberwinkler 2001, Spirin et al. 2020, 2021, pres- ent study — Fig. 1). All Basidiodendron spp. have gloeocystidia similar to those of the cystidiate Protohydnum species. However, the genera are quite different otherwise. Basidiocarps of Basidiodendron spp. are waxy-arid (not gelatinous as in Protohydnum), and they become somewhat gelatinised at the very end of their development in only a few species. Furthermore, tur- gid basidia of Basidiodendron spp. are usually located at the very top of the basidia-bearing hyphae covered by remnants of already collapsed basidial MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 361 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia cells, giving these structures a peculiar “fishbone”-like appearance; no such structures have been observed in Protohydnum spp. Moreover, basidiospores of Basidiodendron spp. feature a large, often asymmetrical, and somewhat eccentric apiculus (at least in the core species of the genus, i.e. those from the Basidiodendron eyrei (Wakef.) Luck-Allen and Basidiodendron caesioci- nereum (Hohn. & Litsch.) Luck-Allen complexes) (Spirin et al. 2020, 2021). In contrast, the basidiospore apiculus in Protohydnum spp. is, as a rule, rather small, regularly outlined, and conventionally located. Protohydnum album (Lloyd) Spirin, comb. nov. MycoBank No: 858676 Figs 7C,11A = Exidiopsis alba Lloyd, Mycological Writings 4 (44): 9, 1913. Lectotype (se- lected here, MBT 10025858). Fig. 1929 (plate 177) in Lloyd, Mycological Writings 6, 1921. Epitype (selected here, MBT 10025859). USA. Ohio: Butler Co., Ross Hanover Rd., Platanus sp., 19.VIl.1977 Burdsall 9422 (CFMR HHB-9422; duplicate — LE 23063%, studied; other duplicates — ILLS 00157217, MIN 840751, NY 01930202). = Seismosarca alba (Lloyd) Lloyd, Mycological Writings 6: 1045, 1921. = Exidia alba (Lloyd) Burt, Annals of the Missouri Botanical Garden 8: 366, 1921. = Gloeotromera alba (Lloyd) Ervin, Mycologia 48 (5): 692, 1956. Description. Basidiocarps first orbicular or pulvinate, later cerebriform or foli- aceous, gelatinous, opalescent, pure white to beige, later pale ochraceous to brownish, up to 3 cm in diam., 3-15 mm thick, in dry condition brown and tough, margin elevated, partly detaching; lobes rounded, entire, 1-1.5 mm thick. Hy- phal structure monomitic, hyphae hyaline, clamped, thin- to slightly thick-walled; context hyphae mostly interwoven, frequently anastomosing, 2-7 um in diam., occasionally swollen at septa (up to 9 um in diam.), embedded in gelatinous matrix, subhymenial hyphae predominantly ascending, rather loosely arranged, 1-3 um in diam. Gloeocystidia abundant, yellowish or brownish, gradually ta- pering to the apex, more rarely narrowly clavate, occasionally bifurcate, embed- ded, (69-) 76-260 (—265) x (4.1—) 5.0-11.4 (-13.2) um (n = 42/4). Hyphidia abundant, richly branched, 0.5—2 um in diam. at the apex, occasionally forming a continuous layer up to 20 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, sessile or very rarely with a strongly reduced stalk-like base (up to 2.5 x 2.5 um), embedded, (12—) 13-17.5 (-18) x (8.8-) 9.1-13.5 (-13.7) um (n = 40/4), sterigmata gradually tapering, up to 15 x 2-3 um. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, often slightly curved, (7.3-) 7.6-11.2 (-12.2) x (3.8—) 3.9-6.1 (—6.2) um (n = 120/4), L = 9.37-10.14, W = 4.63-5.54, Q’ = (1.5-) 1.6-2.3 (-2.4), Q = 1.72-2.04. Distribution and ecology. North America (USA — the eastern states); wood of angiosperms. Remarks. The species was first described as Exidiopsis alba (Lloyd 1913) and then moved to the genus Seismosarca Cooke by Lloyd (1921). Burt (1921) treated E. alba under Exidia. Martin (1951) studied the original mate- rial of Seismosarca hydrophora Cooke, the generic type of Seismosarca, and MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 362 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia concluded that it was an Auricularia species. Consequently, Ervin (1956) placed E. alba, as well as Tremella pululahuana Pat., in a newly established genus, Gloeotromera Ervin. Wells (1957) showed that T. pululahuana is the same species as Ductifera millei, the generic type of Ductifera, which was also described from Pululahua, Ecuador. He therefore moved T. pululahuana to Ductifera and stated that E. alba was conspecific with the former species. We studied both the authentic material of 7; pu/ulahuana from Ecuador and numerous collections of the species so named from the USA. In our opinion, they should be treated separately, and E. alba is to be retained as the correct name for the North American species. Lloyd did not provide any reference to studied specimens of E. alba in the pro- tologue, nor in a later treatment of this species (Lloyd 1913, 1917). Stevenson and Cash (1936) reported 34 specimens in Lloyd’s herbarium labelled as Heter- ochaete alba, Seismosarca alba, or S. albida, but none named E. alba. Specimens identified as E. alba are also lacking in MyCoPortal (Miller and Bates 2017). It is therefore uncertain which collections were at Lloyd’s disposal when he pre- pared the species description. In the original description, he mentioned that anatomical features of E. alba were depicted by E.M. Wakefield (Lloyd 1913: 9). This drawing was published eight years later (Lloyd 1921); we designate it here as a lectotype (iconotype) of E. alba. Additionally, we provide E. alba with an epitype — a recent sequenced collection distributed among several herbaria. Sequences of D. pululahuana published by Weif& and Oberwinkler (2001) ac- tually belong to P album. Differences between these species are discussed under Protohydnum pululahuanum. Protohydnum aureum (Lowy) Spirin, comb. nov. MycoBank No: 858677 Fig. 11B = Ductifera aurea Lowy, Mycologia 68: 1106, 1976. Holotype. Panama. Chiriqui: Cerro Punta, Cerro Respingo, unidentified wood in oak forest, 2.VI.1975 Du- mont & Carpenter PA-1737 (NY00738326, studied). Description. Basidiocarps first pustulate, gregarious, up to 1.5 mm in diam., then adpressed-cerebriform, up to 4 mm in diam., finally fusing together and forming compound crust-like fructifications up to 1 cm in the widest dimension, gelatinous, semitranslucent, amber-yellowish to pale ochraceous, 0.5-1 mm thick, in dry con- dition almost invisible, margin elevated, partly detaching; lobes poorly differen- tiated, rounded, entire, up to 0.5 mm thick. Hyphal structure monomitic, hyphae clamped; context hyphae thin- to slightly thick-walled, predominantly interwoven, hyaline or brownish, 1-4 um in diam., embedded in gelatinous matrix, subhymenial hyphae thin-walled, ascending, hyaline, 1.5-3 um in diam. Gloeocystidia abundant to rather rare, hyaline to yellowish, as a rule gradually tapering to the apex, embed- ded or rarely slightly projecting, 44-85 x 4.3-8.9 um (n = 10/1). Hyphidia abundant, simple or sparsely branched, 0.5-1 um in diam. at the apex, forming a continuous layer up to 10 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, sessile, embedded, 18-24 x 9.7-13.5 um (n = 10/1), sterigmata gradually tapering, up to 15 x 2-3 um. Basidiospores smooth, thin-walled, cylindrical to broadly cylin- MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 363 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia drical, occasionally slightly curved, (10.0—) 10.2-14.6 (—15.4) x 5.5-7.2 (—7.4) um (n = 20/1), L = 12.84, W = 6.46, Q’ = (1.6-) 1.7-2.5 (-2.7), Q = 2.00. Remarks. Ductifera aurea was described from a single specimen collected in Panama (Lowy 1976) and is so far not known elsewhere. Morphologically, it is most similar to P album and P. pululahuanum. It differs from both of these in having considerably larger basidia and basidiospores. We transfer it to Proto- hydnum based on morphological evidence; our attempts to sequence the holo- type were unsuccessful. Protohydnum cartilagineum Moller, Botanische Mittheilungen aus den Tropen 8: 173, 1895. Note. For a modern description of P. cartilagineum, see Malysheva et al. (2018). The species is closely related to P ocellatum introduced below; see further re- marks under the latter species. Protohydnum elasticum (Lowy) Spirin, comb. nov. MycoBank No: 858678 Fig. 11C = Ductifera elastica Lowy, Mycotaxon 15: 97, 1982. Holotype. Brazil. Acre: Rio Branco, rotten wood, 11.X.1980 Lowy BR646 (LSUM, isotype - NY00738327, studied). Description. Basidiocarps effused, up to 3 cm in widest dimension, smooth or indistinctly tuberculate, gelatinous, opaque, dirty ochraceous to brownish, 0.1-0.2 mm thick, in dry condition almost invisible, margin sharply delimited, adnate. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hy- phae thin- to slightly thick-walled, interwoven or subparallel, hardly discernible, 1.5-3.5 um in diam., subhymenial hyphae thin-walled, ascending or interwoven, easily collapsing, 1.5-3 um in diam. Gloeocystidia abundant, hyaline to yellow- ish, tubular-clavate, sometimes gradually tapering to the apex, embedded, (35- ) 36-92 (-—102) x (5.0-) 5.1-8.7 (—8.8) um (n = 14/1). Hyphidia abundant, vari- ably branched, 1-1.5 pm in diam. at the apex, forming a continuous layer up to 10 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedun- culate, 14.5-21 x 9.4-15.2 um (n = 8/1), stalk up to 15 x 3.5—4 um, sterigmata gradually tapering, up to 16 x 3-3.5 um. Basidiospores smooth, thin-walled, broadly cylindrical to narrowly ovoid, slightly to moderately curved, (7.4—-) 7.8- 11.0 (-11.1) x (4.3-) 4.6-5.8 (-6.2) um (n = 30/1), L = 9.10, W = 5.21, Q’ =(1.4- AL 5=I19-(- 2:0), = 1,75: Remarks. The species was described as a member of Ductifera (Lowy 1982), although effused basidiocarps and pedunculate basidia of D. elastica indicate that Bourdotia could have been more appropriate for it. Roberts (2003) studied the type of D. elastica and concluded that it is conspecific with the European Exidiopsis (Bourdotia) galzinii (see under Protohydnum gaizinii below). We re- checked the aforementioned type and concluded that D. elastica is similar to B. galzinii but cannot be considered its synonym. The main difference between MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 364 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia these species is the spore width and shape -— the basidiospores of D. elasti- ca are certainly narrower and more regularly cylindrical than in B. galzinii. We therefore combine D. elastica in Protohydnum as a species of its own. The spe- cies is so far known only from the type locality in the Brazilian Amazon, and no verified sequences of P elasticum currently exist. Protohydnum elevatum V. Malysheva & Spirin, sp. nov. MycoBank No: 858668 Fig. 11D Holotype. Russia. Sakhalin Reg.: Kunashir, Actinidia kolomikta (dry branch), 17.VIII.2017 Bulakh (LE F-347688*%, isotype — H). Etymology. Elevatus (Lat., adj.) — elevated; referred to the basidiocarp margin. Description. Basidiocarps adpressed-orbicular to cerebriform, erumpent, up to 0.5 cm in diam., first solitary, then partly fusing together, gelatinous, semi- translucent, ivory-yellowish or pale ochraceous, up to 1 mm thick, in dry condition brownish and crustaceous, margin elevated, adnate; lobes poorly pronounced, rounded, entire, 0.5-1 mm thick. Hyphal structure monomitic, hyphae hyaline, clamped, thin-walled, easily collapsing; context hyphae interwoven, 2.5-5 um in diam., embedded in gelatinous matrix, subhymenial hyphae ascending or in- terwoven, rather loosely arranged, 2—4 um in diam. Gloeocystidia abundant, hy- aline to yellowish, often distinctly tapering to the apex, embedded, (23-) 26-46 (-51) x (5.2-) 5.3-7.8 (-8.1) um (n = 20/1). Hyphidia abundant, richly branched, 1-1.5 um in diam. at the apex, forming a continuous, loose layer up to 15 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, sessile, often distinctly tapering to the base, embedded, (18-) 24-34 (—40) x (11.8-) 12.0- 15.9 (-16.7) um (n = 20/1), sterigmata gradually tapering, up to 25 x 4-6 um. Ba- sidiospores smooth, thin-walled, ellipsoid-ovoid to broadly cylindrical, more rare- ly cylindrical and slightly curved, (11.0-) 11.8-15.7 (-16.2) x (7.4-) 7.8-10.1 (-11.1) um (n = 30/1), L = 13.16, W = 8.91, Q’ = (1.2-) 1.3-1.7 (-1.8), Q = 1.49. Distribution and ecology. East Asia (Russia — Kuril Ids.); dead angiosperm wood. Remarks. Protohydnum elevatum is a close relative of P lactescens from North America (Figs 1, 2). It differs from the latter species in having larger ba- sidia and wider basidiospores, as well as shorter gloeocystidia. The species is currently known only from the type locality in East Asia. Protohydnum erumpens A. Savchenko & Spirin, sp. nov. MycoBank No: 858669 Figs 6E, 11E Holotype. Kenya. Taita-Taveta: Taita Hills, Ngangao Forest, Xymalos monospo- ra (fallen branch), 23.X1.2017 Savchenko 171123/1515* (H7008774). Etymology. Erumpens (Lat., present participle of ‘erumpo’) — erumpent, in reference to the basidiocarp’s growth. Description. Basidiocarps effused, up to 3 cm in widest dimension, erumpent, smooth, gelatinous, semitranslucent, bluish-greyish to pale ochraceous, 0.04- 0.1 mm thick, in dry condition almost invisible, margin gradually thinning-out. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 365 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Hyphal structure monomitic, hyphae hyaline or yellowish, clamped; subicular hy- phae slightly thick-walled, subparallel, frequently anastomosing, 2-3 um in diam., subhymenial hyphae thin- to slightly thick-walled, interwoven or ascending, rath- er loosely arranged, 2—4 um in diam. Cystidia absent. Hyphidia abundant, richly branched, 0.5-1 um in diam. at the apex, occasionally forming a continuous lay- er up to 15 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, (12—) 13-16.5 (—17) x (9.0—) 9.2-11.2 (-—11.3) pm (n = 20/1), stalk up to 14 x 3-4.5 um, sometimes strongly reduced, sterigmata gradually tapering, up to 20 x 2-3 um. Basidiospores smooth, thin-walled, cylindrical to broadly cy- lindrical, slightly to moderately curved, (8.9—) 9.3-12.3 (-13.4) x (5.0-) 5.1-6.4 (—6.8) um (n = 30/1), L= 11.12, W = 5.78, Q’ = (1.6-) 1.7-2.2 (-2.3), Q = 1.93. Distribution and ecology. Africa (Kenya); partly corticated fallen angiosperm branch. Remarks. Morphologically and phylogenetically, P erumpens is closest to P livescens (Fig. 1). It differs from this species in having thinner basidiocarps, shorter basidia, and slightly smaller basidiospores. Protohydnum erumpens is so far known only from the type locality in Africa, where it was collected from angiosperm wood remnants. In turn, the European species P. livescens seems to be restricted to coniferous hosts. Protohydnum gaizinii (Bres.) Spirin & R.H. Nilsson, comb. nov. MycoBank No: 858679 Figs 7D, 11F = Sebacina galzinii Bres., Annales Mycologici 6: 46, 1908. Lectotype (selected by Wells and Raitviir 1975: 908). France. Aveyron: Saint-Sernin-sur-Rance, Fraxinus excelsior, V.1905 Galzin 3832 (S F19700, studied). = Bourdotia galzinii (Bres.) Torrend, Brotéria Serie Botanica 11: 88, 1913. = Bourdotia caesia Bres. & Torrend, Brotéria Serie Botanica 11: 88, 1913. Lecto- type (selected here, MBT10025860). Portugal. Lisboa, ‘ad ligna’, 27.XII.1909 Torrend (PC0084209, studied). Description. Basidiocarps effused, covering a few cm, smooth or indistinctly tuber- culate, gelatinous, first semitranslucent, bluish-greyish, then opalescent, whitish, 0.1-1 mm thick, in dry condition vinaceous-brown to brownish-black, vernicose, margin gradually thinning-out. Hyphal structure monomitic, hyphae hyaline or yel- lowish, clamped; subicular hyphae thin-walled, subparallel, 3-4 um in diam., subhy- menial hyphae thin-walled, interwoven or ascending, rather densely arranged, 1.5- 3.5 um in diam. Gloeocystidia abundant, brownish-yellowish, deeply rooted, usually tapering to the apex, often sinuous, embedded, (68-) 70-109 (—118) x (4.1-) 4.2- 7.2 (-8.6) um (n = 30/3). Hyphidia abundant, richly branched, 1-1.5 um in diam. at the apex, forming a continuous layer up to 20 um thick. Basidia four-celled, lon- gitudinally or occasionally obliquely septate, ovoid-ellipsoid, pedunculate, (12-) 13-20 (—23.5) x (8.7—) 8.9-13.1 (-14.0) um (n = 41/4), stalk up to 16 x 2.5-3 um, sterigmata tubular, gradually tapering, up to 20 x 2—3.5 um. Basidiospores smooth, thin-walled, ellipsoid-ovoid to broadly cylindrical, the longest spores slightly curved, (8.1—-) 8.3-12.3 (-12.8) x (5.0-) 5.1-7.3 (—7.4) um (n = 180/6), L = 9.32-11.26, W = 6.23-6.48, Q’ = (1.2—) 1.3-2.0 (—2.3), Q = 1.49-1.75. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 366 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Distribution and ecology. Europe (Austria, France, Germany, Italy, Portugal, Russia, Spain, and Ukraine), Macaronesia (Canary Islands), and Asia (Iran); de- corticated wood of deciduous trees, rarely conifers. Remarks. This species was first described as a member of the simulta- neously introduced subgenus Bourdotia Bres. in the genus Sebacina Tul. & C. Tul. (Bresadola 1908). Five years later, the subgenus was raised to the genus rank, and another species, B. caesia, was added (Torrend 1913). We studied type material of both species and concluded that they are conspe- cific. Here we treat Bourdotia as a synonym of Protohydnum and therefore transfer B. galzinii to the latter genus. Protohydnum gaizinii is a temperate species widely distributed in Europe. Due to its prominent gloeocystidia and stalked basidia, it can be easily iden- tified under the microscope. The identity of B. gal/zinii collections from North and South America, as well as that of Bourdotia petiolata (D.P. Rogers) K. Wells, originally described from the Marshall Islands, remains obscure due to the lack of recent sequenced material. Bourdotia galzinii f. microcystidiata Hauerslev was described based on a single collection (Galzin 14319, PC) ini- tially identified by Bourdot as Sebacina mesomorpha Bourdot & Galzin (Hau- erslev 1993). We restudied this specimen and concluded that it belongs to Exidiopsis opalea (Bourdot & Galzin) D.A. Reid. Protohydnum glabrum (Moller) Spirin, comb. nov. MycoBank No: 858680 = Exidiopsis glabra Moller, Botanische Mittheilungen aus den Tropen 8: 168, 1895. Lectotype (selected here, MBT 10025861). Brazil. Santa Catarina, Blu- menau, 8.11.1893 Moller 1039 (HBG, studied). Description. Basidiocarps effused, covering a few cm, smooth, gelatinised, semitranslucent, dirty ochraceous to brownish, 0.1-0.2 mm thick, mar- gin gradually thinning-out. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hyphae indiscernible, subhymenial hyphae thin-walled, ascending, easily collapsing, 2.5-3.5 um in diam. Gloeocystidia yellow- ish, tapering, embedded, 41-69 x 6.5-12 um. Hyphidia abundant, richly branched, 1-1.5 um in diam. at the apex, forming a continuous layer up to 20 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, 14.5-18 x 9.1-12.8 um (n = 6/1), stalk up to 17 x 3-3.5 um, sometimes strongly reduced, sterigmata gradually tapering, up to 12.5 x 3 um. Basidiospores smooth, thin-walled, broadly ellipsoid to subglobose, 8.0-10.2 x 6.7-7.9 um (n = 3/1), widely collapsed. Remarks. This species was described by Moller (1895) as a member of Exidiopsis from the southern part of Brazil and never mentioned thereafter. Here we reassess it based on the morphological study of the single remain- ing specimen in the HBG herbarium (designated as the lectotype above). The completely effused, smooth basidiocarps, abundant gloeocystidia, and ovoid-ellipsoid, clearly stalked basidia point towards Bourdotia galzinii (= Protohydnum gaizinii in the present study) and satellite species as closest to P glabrum. Among these species, P nudum from East Africa looks most MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 367 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia similar to P glabrum. These species can be separated based on the length of gloeocystidia (twice as long in RP nudum compared to P. glabrum) and the presence of distinct, thick epihymenial layer of hyphidia in P glabrum. Protohydnum glabrum is so far known only from the type locality, and newly collected material is highly desirable to study it with DNA methods. Protohydnum lactescens (Burt) Spirin & V. Malysheva, comb. nov. MycoBank No: 858681 Figs 10A,11G = Sebacina lactescens Burt, Annals of the Missouri Botanical Garden 13: 336, 1926. Holotype. Grenada. Grand Etang, [angiosperm branch], 1912-1913 Thaxter 153 (FH00488322, studied). Description. Basidiocarps first adpressed-orbicular, up to 1 cm in diam., ge- latinous, semitranslucent, pale ochraceous or greyish to brownish, 1-2 mm thick, then fusing together and forming compound effused basidiocarps up to 5 cm in diam., in dry condition brown and rather tough, margin adnate or partly detaching. Hyphal structure monomitic, hyphae hyaline, clamped; con- text hyphae thin-walled, interwoven or subparallel, anastomosing, embedded in gelatinous matrix, 2-4 um in diam., subhymenial hyphae thin-walled, as- cending or interwoven, 1.5-3 um in diam. Gloeocystidia abundant, hyaline to yellowish or brownish, tapering or more rarely tubular-clavate, embedded or only slightly projecting (up to 10 um) above hymenial layer, 48-112 x 5-11 um. Hyphidia abundant, richly branched, 1-2 pm in diam. at the apex, form- ing a continuous layer up to 25 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, sessile or rarely with a reduced stalk up to 4 x 3 um, (18-) 19-26.5 (-29) x (10.8-) 11.7-16.0 (-18.0) um (n = 30/3), sterigmata gradually tapering, up to 20 x 3.5-4 um. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, occasionally slightly curved, (9.4—) 9.9-15.6 (-16.8) x (5.8-) 5.9-8.3 (-8.9) um (n = 90/3), L = 13.05-14.04, W = 6.77- 7.33, Q =(1:4-) 15-24 (=2;5),0:= 1:78-1,99. Distribution and ecology. North America (USA — California, the Caribbean — Grenada); decayed angiosperm wood. Remarks. This species was originally described from the Caribbean (Burt 1926) and later placed among the synonyms of Ductifera sucina (Wells 1957). We restudied the type specimens of both Sebacina lactescens and Exidia sucina (see under Protohydnum sucinum below) and concluded that they belong to two different species. Protohydnum lactescens produces ef- fused basidiocarps, while they are cerebriform-exidioid in P sucinum. Mi- croscopically, the species can be easily separated based on size of gloeo- cystidia (much shorter in P lactescens than in P sucinum), basidia, and basidiospores (considerably larger in P lactescens than in P sucinum). DNA sequences of D. sucina published by Weif& and Oberwinkler (2001) and Wells et al. (2004) represent P lactescens instead. Wells (1957) listed Exidia cys- tidiata Olive as another synonym of D. sucina. We did not study its type; as we could judge from the protologue, it is likely that E. cystidiata is a synonym of P lactescens. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 368 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia ri Figure 10. Microscopic structures of: A. Protohydnum lactescens (specimen TAAM192048) (hymenial cells and tramal hy- phae); B. P. livescens (specimen Spirin 13913) (hymenial cells and subhymenial hyphae); C. P. pallidum (holotype) (gloeo- cystidia and a basidium); D. P sucinum (lectotype) (1 — basidia and basidiospores; 2 — gloeocystidia). Scale bar: 10 um. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 369 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia > B J C K D L E M F N G O CG} Figure 11. Basidiospores of: A. Protohydnum album (specimen Miettinen 196583); B. PR aureum OU! C. P elasticum (holotype); D. PR elevatum (holotype); E. P erumpens (holotype); F. P. galzinii (three left - specimen Miettinen 15900.4, three right — lectotype of S. galzinii); G. P lactescens (four left - specimen TAAM192048, three right — holotype of S. /ac- tescens); H. P. livescens (specimen Spirin 13913); |. R microperum (holotype); J. RP nudum (holotype); K. P. ocellatum (holotype); L. P. pallidum (holotype); M. P pululahuanum (three left — lectotype, three right - specimen FH00783538); N. P. sucinum (three left — lectotype of A. brasiliensis, three right - specimen BPI 701268); O. Protomerulius amiliavi (ho- lotype); P. P deceptorius (holotype). Scale bar: 10 um. Protohydnum livescens (Bres.) Spirin & V. Malysheva, comb. nov. MycoBank No: 858682 Figs 6F, 10B, 11H = Sebacina livescens Bres., Fungi Tridentini 2 (11-13): 64, 1898. Lectotype (se- lected here, MBT 10025862). Italy. Trentino-Alto Adige: Trento, Andalo, Abies alba (rotten log), VIII.1896 Bresadola (S F29132, studied). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 370 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia = Exidiopsis livescens (Bres.) Bourdot & Maire, Bulletin de la Société My- cologique de France 36: 71, 1920. = Sebacina laccata Bourdot & Galzin, Bulletin de la Société Mycologique de France 39: 262, 1924. Lectotype (selected by Hauerslev 1993). France. Avey- ron: Millau, LHospitalet-du-Larzac, Pinus sp., 25.1V.1910 Galzin 5743 (herb. Bourdot 7199) (PC, studied). Description. Basidiocarps effused, covering a few cm, smooth or indistinctly tuber- culate, gelatinous, first semitranslucent, whitish-greyish or cream-coloured, then greyish- to reddish-brown, opalescent, 0.02—1 mm thick, in dry condition almost invisible or turning to a vinaceous-brown vernicose crust, margin rather sharply de- limited, adnate. Hyphal structure monomitic, hyphae hyaline or yellowish, clamped; subicular hyphae thin- to slightly thick-walled, interwoven or subparallel, frequent- ly anastomosing, 2-4 um in diam., subhymenial hyphae thin- to slightly thick- walled, interwoven or ascending, rather densely arranged and partly glued together, 1-3.5 um in diam. Cystidia absent. Hyphidia abundant, richly branched, 0.5-2 um in diam. at the apex, usually forming a continuous layer up to 20 um thick. Basidia four-celled, longitudinally or rarely obliquely septate, ovoid-ellipsoid, pedunculate, (13-) 14-20 (—22) x (9.7—) 9.8-14.3 (-14.5) um (n = 72/7), stalk up to 15 x 2-4 um, sometimes strongly reduced, sterigmata tubular, gradually tapering, up to 20 x 2-3.5 um. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, of- ten slightly curved, (9.1—) 9.2-15.8 (-15.9) x (4.7—) 5.0-7.2 (—7.3) um (n = 240/8), L = 11.34-13.65, W = 5.71-6.46, Q’ = (1.6-) 1.7-2.6 (-2.8), Q = 1.85-2.23. Distribution and ecology. Europe (Austria, France, Greece, Italy, Romania, Slo- venia, Spain, and Ukraine); rotten decorticated wood of conifers (Abies, Pinus). Remarks. The species was originally introduced as a member of Sebacina ac- companied by a peculiar conidial stage, Dendrodochium livescens Bres. (Bresa- dola 1898). The authentic material is currently stored in two parcels in Stockholm. We studied them both and concluded that these specimens belong to two differ- ent species. The Dendrodochium stage is certainly an asexual (Leucogloea) stage of a Helicogloea species (cf. Kirschner 2004, Spirin et al. 2018b); we will address its identity on a separate occasion. The teleomorphic fungus does represent a genuine member of the Auriculariales with four-celled, petiolate basidia, and it is evidently conspecific with Exidiopsis laccata Bourdot & Galzin. According to DNA data, S. livescens belongs to Protohydnum, and it is most closely related to P erumpens from Africa and two neotropical species, P. cartilagineum (the gener- ic type of Protohydnum) and P. ocellatum described below. The lack of gloeocys- tidia and longer basidiospores differentiate P livescens from P galzinii, another representative of the genus in central and southern parts of Europe. The lectotype of S. laccata described from southern France (Bourdot and Galzin 1924) is mor- phologically indistinguishable from the type of S. livescens and other specimens studied by us; S. laccata is therefore treated here as a synonym of P livescens. Neuhoff (1936) misapplied the name S. livescens to another species, which is distributed in northern Eurasia. The correct name for the latter taxon is Exid- iopsis succinea K. Wells & Raitviir (see description in Wells and Raitviir 1987). It differs from P. livescens in having sessile (not pedunculate) basidia, larger basidiospores, and it occurs on angiosperms, preferably on wood of Salicace- ae. Phylogenetically, these species are not closely related (Fig. 1). All previous records of E. livescens from northern Europe seem to refer to E. succinea. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 37] Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Protohydnum microperum (Kalchbr. & Cooke) Spirin, comb. nov. MycoBank No: 858683 Fig. 111 = Tremella micropera Kalchbr. & Cooke, Grevillea 9 (49): 18, 1880. Holotype. South Africa. Eastern Cape: Blue Crane Route, Somerset East, on branches, [no collecting date] MacOwan 1351 (K(M) 56709, studied). Description. Basidiocarps cushion-shaped, gregarious, erumpent, ca. 1 mm in diam., gelatinous, semitranslucent, amber-coloured, up to 0.5 mm thick, in dry condition reddish-brown. Hyphal structure monomitic, hyphae hyaline, clamped, thin- or moderately thick-walled, ascending, 1.5-2.5 um in diam., context hyphae not differentiated. Gloeocystidia abundant, hyaline or brownish, gradually taper- ing to the apex, embedded or slightly projecting, 32-83 x 4.7—9.9 um (n= 10/1). Hyphidia abundant, richly branched, 1-1.5 pm in diam. at the apex, forming a continuous layer up to 20 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, sessile, embedded, 15-23.5 x 9.8-14.2 um (n = 12/1), sterigma- ta gradually tapering, up to 20 x 2.5-3 um. Basidiospores smooth, thin-walled, cylindrical, slightly or distinctly curved, (9.8—-) 10.3-15.3 (-15.8) x (4.5-) 4.6- 6.5 (-6.6) um (n = 30/1), L = 13.31, W = 5.62, Q’ = (1.8—-) 1.9-2.8 (-3.3), Q = 2.39. Remarks. Anatomically, P microperum shows a certain similarity to P aure- um. These species can primarily be separated based on basidiocarp morpholo- gy (cushion-shaped and non-fusing in P microperum versus pustulate and soon coalescing in P aureum) and the basidiospore width (spores in P microperum are on average narrower than in P aureum). Protohydnum microperum is cur- rently known only from the type locality in South Africa. Wells (1958) moved the species to Ductifera and treated Seismosarca tomentosa Olive, described from Georgia (USA), as its later synonym. As we could judge from the protologue (Olive 1947), S. tomentosa has a completely different basidiocarp configuration (effused, strongly darkening after drying, and possessing a white tomentose margin) and much larger basidiospores than P microperum. It seems that the description of D. micropera by Wells (1957) refers mainly to S. tomentosa. After studying the type material of P microperum, we found that they could hardly be conspecific; S. tomentosa certainly deserves a closer study. Protohydnum nudum §Spirin & Ryvarden, sp. nov. MycoBank No: 858670 Fig. 11J Holotype. Kenya. Western Province: Kakamega Forest, decayed wood, 25- 27.1.1973 Ryvarden 9435* (0, isotype — H). Etymology. Nudus (Lat., adj.) — nude; in reference to exposed basidia. Description. Basidiocarps effused, up to 4 cm in widest dimension, smooth, gelatinous, semitranslucent, bluish-greyish to brownish, 0.1-0.2 mm thick, in dry condition light grey and rather sturdy, opaque, margin gradually thin- ning-out. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hy- phae thin-walled or with variably thickened gelatinised walls, subparallel or in- terwoven, glued together, 2.5-4 um in diam., subhymenial hyphae thin-walled, MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 379 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia predominantly ascending, often glued, 2-4 um in diam. Gloeocystidia abun- dant, hyaline to yellowish, deeply rooted or arising from subhymenial hyphae, slightly tapering to the apex, often sinuous, normally embedded, 30-154 x 3.5-6.5 um. Hyphidia abundant, richly branched, 0.5-1 um in diam. at the apex, normally scattered among basidia, in senescent hymenium sometimes forming a continuous layer up to 10 um thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, (17—) 17.5-23 (—24) x (10.2-) 10.3-12.4 (-12.8) um (n = 20/2), often exposed, stalk up to 20 x 3.5—6 (—8) um, sterigma- ta tubular, gradually tapering, up to 18 x 2—3.5 um. Basidiospores smooth, thin- walled, ellipsoid-ovoid to broadly ellipsoid or more rarely subglobose, (7.2-) 7.3-10.2 (-—10.6) x (5.7-) 6.2-8.9 (—9.0) um (n = 60/2), L = 8.65-9.29, W = 6.86-7.91, Q’ = 1.1-1.4 (-1.5), Q = 1.18-1.26, apiculus occasionally eccentric. Distribution and ecology. Africa (Kenya); decorticated wood of deciduous trees. Remarks. Phylogenetically, P nudum is closely related to P. galzinii (Fig. 2). It differs from the latter species in having wider, predominantly ellipsoid basid- iospores and larger basidia. Moreover, basidial cells of P nudum are often ex- posed, while they are normally rather deeply embedded in the layer of hyphidia in P. galzinii. Protohydnum nudum is known only from two collections from East Africa (Kenya); the range of P galzinii lies further to the north, stretching from Macaronesia to the Caucasus and Middle East Asia. Protohydnum ocellatum Alvarenga & K.H. Larss., sp. nov. Fig. 11K MycoBank No: 858671 Holotype. Brazil. Rond6nia: Porto Velho, Cuniao Ecological Station, angiosperm wood in lowland rain forest, 13.III.2012 Larsson 15431* (URM). Etymology. Ocellatus (Lat., adj.) — ocellate; in reference to abundant mineral inclusions. Description. Basidiocarps effused, up to 10 cm in widest dimension, tu- berculate, gelatinous, semitranslucent, amber-yellow to ochraceous-reddish, 0.5-1 mm thick, containing numerous small whitish grains, in dry condition vinaceous-brown, vernicose, margin sharply delimited, adnate or partly de- taching. Hyphal structure monomitic, hyphae hyaline, clamped, thin-walled, homogeneous throughout, ascending, rather tightly arranged, 3-5 um in diam. Cystidia absent. Hyphidia abundant, richly branched, 1-1.5 um in diam. at the apex, usually forming a continuous layer up to 15 um thick. Ba- sidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, (12-) 13-14.5 (-15) x (8.2-) 8.8-11.1 (-11.3) um (n = 20/1), stalk up to 30 x 3-5 um, sterigmata gradually tapering, up to 12 x 3-4 um. Basidiospores smooth, thin-walled, cylindrical to subfusiform, (7.7-) 7.9-10.2 (-10.3) x (3.1-) 3.6-4.8 (-4.9) um (n = 30/1), L = 8.91, W = 4.07, Q’ = (1.8-) 1.9-2.6 (-2.7), Q = 2.20, cytoplasm usually aguttulate. Distribution and ecology. South America (Brazil); decayed angiosperm wood. Remarks. Protohydnum ocellatum is introduced here as a sibling species of P cartilagineum (Figs 1, 2). The species are confusingly similar under the mi- croscope, and they are phylogenetically closely related. The only reliable mor- phological difference is the hymenophore construction: the hymenophore is MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 373 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia nearly smooth in P. ocellatum but consists of robust (up to 3 mm long), regularly distributed spines in P cartilagineum. Nevertheless, this striking macroscopic difference and the substantial genetic distance (2.6% difference in the LSU re- gion) allow us to distinguish between these two species. Protohydnum ocella- tum has so far only been found in the type locality in Brazil. Protohydnum pallidum Spirin & Ryvarden, sp. nov. MycoBank No: 858672 Figs 10C, 11L Holotype. Zimbabwe. Manicaland: Rhodes Inyanga Nat. Park, Nyazengu, corti- cated hardwood branch, 16.1.1989 Ryvarden 26180* (0, isotypes — H, LE). Etymology. Pallidus (Lat., adj.) — pale, in reference to pale-coloured basidiocarps. Description. Basidiocarps effused, erumpent, up to 6 cm in widest dimension, smooth or indistinctly folded, cartilagineous, opaque, cream-coloured to pale ochraceous, 1-1.5 mm thick, in dry condition brown, vernicose, margin sharp- ly delimited, sometimes slightly elevated, adnate or partly detaching. Hyphal structure monomitic, hyphae hyaline, clamped, homogeneous throughout, as- cending or interwoven, embedded in gelatinous matrix, 2-3 um in diam. Gloeo- cystidia abundant, yellowish-brownish, tapering or tubular-clavate, embedded, 85-165 x 9.5-17 um. Hyphidia abundant, richly branched, 1.5-2 um in diam. at the apex, forming a continuous layer up to 15 um thick. Basidia four-celled, lon- gitudinally septate, ovoid-ellipsoid, pedunculate, (22—) 23-31 (-32) x (14.2-) 14.4-19.8 (—20.2) um (n = 20/1), stalk up to 22 x 4—5.5 um, sterigmata grad- ually tapering or apically swollen, up to 17 x 6-7 um. Basidiospores smooth, thin-walled, ellipsoid to broadly ellipsoid, (14.0-) 14.7-17.1 (-17.2) x (10.1-) 10:2=13.0 (=1351) pm (nis 30/1), L-= 15.77, W = 11.58," =. (1.1=) 1,2=1.5 (-1.7), Q = 1.37, cytoplasm with one or several large oil drops. Distribution and ecology. Africa (Zimbabwe); still corticated angiosperm branches. Remarks. The species is introduced here based on extensive material collected in southern Africa. Morphologically, P pallidum is reminiscent of the Australian Sebacina megaspora G.W. Martin, combined in Ductifera by Wells (1957). However, Ductifera megaspora (G.W. Martin) K. Wells has sessile, subglobose basidia and much larger basidiospores than those of P. pallidum (see descriptions in Martin 1936 and Wells 1957). The identity of D. megaspora remains obscure. Protohydnum pululahuanum (Pat.) Spirin, comb. nov. MycoBank No: 858684 Fig. 11M = Tremella pululahuana Pat., Bulletin de la Societé Mycologique de France 9: 138, 1893. Lectotype (selected here, MBT 10025863). Ecuador. Pichincha: Quito, Pululahua, decayed branches, II.1892 Lagerheim (FH00783541, studied). = Ductifera pululahuana (Pat.) Donk, Taxon 7: 164, 1958. = Ductifera millei Lloyd, Mycological Writings 5: 711, 1917 (fide Wells 1957). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 374 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia Description. Basidiocarps first pustulate, gregarious, ca. 1 mm in diam., then adpressed-orbicular, up to 1 cm in diam., finally fusing together and forming compound crust-like, effused fructifications up to 2 cm in the widest dimen- sion, gelatinous, semitranslucent, cream-coloured to ivory-yellowish or pale ochraceous, 1-2 mm thick, in dry condition brown and crustaceous, margin elevated, partly detaching; lobes rounded or evenly incised, hollow, 0.5-1 mm thick. Hyphal structure monomitic, hyphae hyaline, clamped, thin- to slightly thick-walled; context hyphae interwoven or subparallel, 2-6.5 um in diam., embedded in gelatinous matrix, subhymenial hyphae predominantly ascend- ing, rather tightly arranged, 1-3 um in diam. Gloeocystidia abundant to rather rare, hyaline to yellowish or brownish, gradually tapering to the apex, embed- ded, (55-) 65-122 (-172) x (5.0-) 5.8-11.4 (-12.3) um (n = 24/3). Hyphidia abundant, richly branched, 0.5-1.5 pm in diam. at the apex, forming a continu- ous layer up to 30 um thick. Basidia four-celled, longitudinally septate, ovoid-el- lipsoid, sessile, embedded, (12-) 13.5-17.5 (-18.5) x (8.9-) 9.8-13.6 (—13.8) um (n = 24/3), sterigmata gradually tapering, up to 15 x 2-3 um. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, usually slightly curved, (8.4—) 8.8-11.8 (-12.3) x (4.0-) 4.2-6.5 (—6.6) um (n = 90/3), L = 10.02-10.34, W = 5.36-5.56, Q’ = (1.5—-) 1.6-2.3 (-2.8), Q = 1.85-1.93. Distribution and ecology. South America (Ecuador); thin fallen branches of angiosperms. Remarks. Tremella pululahuana was described from Ecuador by Patouillard and Lagerheim (1893). Four original specimens (FH) are the source of the spe- cies description above, and one of them (with the collecting date indicated on the label) is selected as a lectotype. No sequences of T. pululahuana s. typi are available at the moment, and we therefore combine it in Protohydnum based on morphological evidence, i.e. its high similarity to P album and P. aureum. Protohydnum aureum clearly differs from both P album and P. pululahuanum in having larger basidia and basidiospores. Basidiospores of P pululahuanum are on average slightly longer and wider than in P. album, although their dimensions strongly overlap. Ervin (1956) pointed at macroscopic differences between P album and P. pululahuanum (both treated under Gloeotromera), and her obser- vations correspond with our evidence. Basidiocarps of P pululahuanum are substantially smaller than in P album and, when fully developed, produce hol- low lobes. It seems that yellowish-ochraceous colouration is characteristic of P pululahuanum from the very beginning (see protologue). Fructifications of P album are initially white and either remain so or get yellow-brown tints at the very end of their development or after drying. Moreover, mature basidiocarps of P album are cerebriform, or foliaceous, not adpressed-orbicular or effused as in P. pululahuanum, and they bear entire lobes. Protohydnum sucinum (Moller) Spirin & Alvarenga, comb. nov. MycoBank No: 858685 Figs 10D, 11N = Exidia sucina Moller, Botanische Mittheilungen aus den Tropen 8: 169, 1895. Lectotype (selected here, MBT 10025864). Brazil. Santa Catarina, Blumenau, [1892] Moller 8 (HBG, studied). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 375 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia = Auricularia brasiliensis Lloyd, Mycological Writings 5: 785, 1918. Lectotype (selected here, MBT 10025884). Brazil. [no locality and collecting date], Rick (Lloyd’s herbarium #33208) (BPI701266, studied). Description. Basidiocarps pulvinate or cerebriform, up to 1 cm in diam., occasion- ally fusing together and producing compound fructifications up to 4 cm in widest dimension, gelatinous, semitranslucent, pale ochraceous or amber-coloured to brownish-orange, 1.5-8 mm thick, in dry condition brown and tough, margin ele- vated, partly detaching; lobes rounded, blunt, entire, up to 1.5 mm thick. Hyphal structure monomitic, hyphae hyaline or yellowish, clamped, thin-walled or with a distinct wall; context hyphae predominantly interwoven, 1-3 um in diam., occa- sionally inflated up to 6 um in diam., embedded in gelatinous matrix, subhyme- nial hyphae ascending, rather loosely arranged, 1-3 um in diam. Gloeocystidia abundant, brownish, distinctly tapering at the apex, sometimes subulate, embed- ded or variably projecting, (75-) 80-248 (—272) x (4.0-) 4.2-10.6 (-11.1) um (n = 30/4). Hyphidia hyaline to brownish, richly branched, 0.5-1 um in diam. at the apex, forming a continuous layer up to 50 um thick. Basidia four-celled, lon- gitudinally or obliquely septate, ovoid-ellipsoid, sessile or rarely with a strongly reduced stalk up to 4 x 3 um, (11.5-) 12-16.5 (-17) x (7.8-) 8.1-12.4 (-13.7) um (n = 40/4), sterigmata gradually tapering, up to 30 x 3-4 um. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, usually slightly curved (bean-shaped), (8.3—) 8.8-11.0 (—11.1) x (4.7—) 4.8-6.1 (—6.3) um (n = 120/4), L = 9.99-10.75, W = 5.23-5.53, Q’ = (1.5-) 1.6-2.4 (-2.6), Q = 1.83-1.99. Distribution and ecology. South America (southern part of Brazil); decayed wood of angiosperms. Remarks. The authentic specimen of E. sucina, as well as many other of Moller’s collections, was noted as being present in the HBG herbarium by Friedrichsen (1977) but never properly investigated. We studied it and formally designated the specimen as a lectotype of E. sucina. Morphologically, P sucinum is most similar to P lactescens; their differences are listed under that species. Three original spec- imens of Auricularia brasiliensis (all collected by Rick in Brazil) in Lloyd’s herbarium (BPI) belong to P sucinum sensu typi; we therefore place A. brasiliensis among the synonyms of P sucinum. No modern specimens of P sucinum are known to us. Protohydnum sp. Vlasak 1808/145 Description. Basidiocarps effused, up to 4 cm in widest dimension, smooth, cartilagineous, Opaque, cream-coloured, with pinkish or brownish stains, 0.5-1 mm thick, in dry condition greyish, often with ochraceous or brownish spots, crust-like, margin sharply delimited, adnate or partly detaching. Hyphal structure monomitic, hyphae hyaline, clamped, thin- or slightly thick-walled, homogeneous throughout, tightly interwoven, and strongly glued together, 1.5-2.5 um in diam. Cystidia absent. Probasidia clavate, embedded, 12-15 x 6-7 um. Mature basidia and basidiospores not observed. Remarks. In our phylogenetic analyses, this unnamed taxon appears as a sister species of P. cartilagineum and P. ocellatum (Figs 1, 2). However, the sin- gle studied specimen collected in French Guiana is sterile, and we therefore leave it without a formal description. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 376 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Protomerulius Moller, Botanische Mittheilungen aus den Tropen 8: 129, 1895. Note. For a treatment of this genus, see Spirin et al. (2019c). Type species. Protomerulius brasiliensis Moller. This genus was recently amended to include half-pileate poroid, effused odontioid, and corticioid taxa possessing stalked basidia and firm hyphae; these hyphae enter into a hymenial layer as thick-walled cystidia in effused species or form an axis of tube dissepiments in poroid species (Spirin et al. 2019c). Here we describe two more corticioid species from Europe and reassess Protomeru- lius commotus Spirin & V. Malysheva based on more extensive material. Protomerulius amiliavi Spirin, sp. nov. MycoBank No: 858673 Figs 66,110 Holotype. France. Aveyron: Millau, Le Causse Noir, Quercus pubescens (fallen decorticated branch), 13.X|.2022 Spirin 16165* (H, isotype — PC). Etymology. From Amiliavum, the Roman name of Millau (the type locality). Description. Basidiocarps effused, smooth, waxy, greyish to greyish-ochraceous, continuous, in older parts light-brown and partly gelatinised, up to 5 cm in wid- est dimension, 0.1-0.2 mm thick, margin narrow, first whitish to cream-coloured, floccose, then more compact and more or less concolourous with the hymenial surface. Hyphal structure monomitic; hyphae clamped, subicular hyphae with a distinct wall to slightly thick-walled, interwoven to subparallel, 1-3 um in diam., subhymenial hyphae thin-walled, interwoven or ascending, 1-2 yum in diam., part- ly glued together. Tramal cystidia abundant, hyaline or brownish, tubular-clavate, sturdy, arising from slightly thick-walled, narrow hyphae, with moderately thickened (up to 1.5 um) walls gradually thinning-out towards the apical part, longest cystidia slightly tapering to or widened at the apex (thin-walled apical parts sometimes col- lapsing), (32—) 35-103 (-119) x (2.8-) 3.3-5.2 (—5.3) um (n = 42/2), oftenin groups of 5-15. Hyphidia present, simple or sparsely branched, 1-1.5 um in diam. at the apex. Crystals present, acicular or in stellate agglomerations, up to 15 um in wid- est dimension. Basidia four-celled, longitudinally septate, ovoid-ellipsoid to subglo- bose, pedunculate, (7.8-) 8.2-11.2 (-11.8) x (6.4-) 7.1-8.8 (—9.0) um (n = 40/2), partly glued together, stalk distinct, up to 5 x 2.5 um, sterigmata up to 10 x 2 um. Basidiospores ellipsoid to broadly ellipsoid, more rarely broadly cylindrical, the lon- gest spores somewhat sigmoid, (5.9—) 6.0-9.1 (—9.4) x (3.5—-) 3.7-5.1 (-5.2) um (n = 62/2), L = 7.30—7.59, W = 4.25—4.39, Q’ = (1.3-) 1.4-2.1 (—2.3), Q = 1.67-1.80. Distribution and ecology. Europe (France); decayed angiosperm wood (Quercus). Remarks. Here we introduce P amiliavi as a close relative of P brachysporus (Bourdot & Galzin) Spirin & Malysheva. Both species possess rather thick, nor- mally smooth basidiocarps with a gelatinised, light-brown when mature hyme- nium and rather narrow, fasciculate cystidia. Protomerulius amiliavi differs from P brachysporus in having shorter and narrower cystidia and in lacking skeletal hyphae (although they are present only in well-developed specimens of the lat- ter species). Moreover, P. amiliavi was collected from rotten oak wood, and all verified records of P brachysporus were collected on conifer wood. MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 377 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia There are two other angiosperm-dwelling European Protomerulius species that produce opaque and relatively thick, crust-like basidiocarps and thereby can be mistaken for P. amiliavi. Of them, Protomerulius dubius (Bourdot & Galz- in) Spirin & Malysheva is most similar to P amiliavi, both macroscopically, due to its partly gelatinised and brownish basidiocarps in maturity, and microscop- ically, having similar cystidia and nearly identical basidiospores. However, cys- tidia of P dubius are perceptibly wider than in P. amiliavi, reaching 9 um in diam., and they are usually arranged in groups of up to eight. Protomerulius pertusus Malysheva & Spirin has loose, nearly floccose basidiocarps occasionally ac- quiring gelatinised spots on the hymenial surface only at the very end of their development. The cystidia of P pertusus are of nearly the same diameter as in P amiliavi, but its basidiospores are clearly narrower (W = 3.49-4.01). Protomerulius commotus Spirin & V. Malysheva, Mycological Progress 18: 1087, 2019. Holotype. Norway. Vestfold: Larvik, Kvelde, Jordstayp, Ulmus glabra (rotten log), 15.1X.2016 Spirin 11097* (O, studied). Description. Basidiocarps effused, smooth, first pruinose-reticulate, waxy, semitranslucent, greyish, then continuous, gelatinised, greyish or brownish when old or dry, up to 2 cm in widest dimension, 0.05-0.1 mm thick, margin con- colourous with hymenium, gradually thinning-out. Hyphal structure monomitic; hyphae clamped, subicular hyphae with a distinct wall, subparallel and densely packed, 1—2.5 um in diam., subhymenial hyphae thin-walled, interwoven or as- cending, 1.5-3 um in diam., often short-celled, glued together. Tramal cystidia abundant, hyaline or brownish, tubular-clavate, sturdy, arising from thin-walled hyphae, with thickened (up to 3.5 um) walls gradually thinning-out towards the apical part, the longest cystidia slightly tapering to or widened at the apex (thin- walled apical parts often collapsing), (54-) 57-149 (-—154) x (4.2-) 4.6-9.4 (-11.3) um (n = 101/5), single or more often in groups of 2-8, sometimes birad- icate, some cystidia tortuous; hymenial cystidia hyaline, broadly clavate to sub- globose, thin- or slightly thick-walled, 10-50 x 4—13.5 um, scattered among ba- sidia, more rarely associated with tramal cystidia. Hyphidia present, simple or sparsely branched, 1-1.5 um in diam. at the apex. Crystals occasionally present on hyphidia and cystidia, acicular or fused in stellate agglomerations. Basidia four-celled, longitudinally septate, ovoid-ellipsoid to subglobose, pedunculate, (6.8-) 7.1-9.1 (-9.4) x (5.9-) 6.2-7.8 (-8.2) um (n = 30/3), spaced or partly glued together, stalk distinct, up to 6 x 2.5 um, sterigmata up to 8 x 2—2.5 um. Basidiospores smooth, thin-walled, ellipsoid to broadly cylindrical, more rarely lacrymoid, (4.1-) 4.4-6.8 (-7.1) x (3.0-) 3.2-4.3 (-4.4) um (n = 180/6), L = 5324-5'95,W.= 3,45-3:85;.Q' =(12=) 193-17. (=1.9),/O=1.47-1.61; Distribution and ecology. Europe (France, Italy, Norway, Sweden, and Swit- zerland — basidiocarps on wood; Czech Republic, Estonia, Germany, and United Kingdom — soil sequences); strongly decayed wood of deciduous trees (Carpi- nus, Fraxinus, Quercus, and Ulmus). Remarks. Protomerulius commotus was described based on two collections from Norway as a close relative of the widely distributed Protomerulius madidus Spirin & K.H. Larss. (Spirin et al. 2019c). Here we reassess it after investigating MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 378 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia newly collected material and detecting one more closely related species, P. de- ceptorius (described below). Macroscopically, R commotus differs from the two aforementioned species due to the lack of white mineral inclusions usually detectable without a lens; however, they are present only in mature basidio- carps of those species. Both Protomerulius commotus and P. deceptorius have broadly clavate or bubble-like hymenial cystidia, in addition to tubular thick- walled cystidia of tramal origin. Protomerulius madidus is devoid of hymenial cystidia, and its basidiospores are on average larger than in P commotus and P deceptorius (see description in Spirin et al. 2019c). Differences of P commo- tus from P. deceptorius are given under the latter species. Protomerulius com- motus seems to be widely distributed in temperate forests of Europe (Fig. 4), but it is most likely overlooked due to its diminutive basidiocarps. Protomerulius deceptorius Spirin & Viner, sp. nov. MycoBank No: 858674 Figs 6H, 11P Holotype. Slovenia. Kocevje: Podstenice, Rajhenavski Rog, Fagus sylvatica (rot- ten decorticated log), 19.VIII.2021 Spirin 14811* (H, isotype — LJF). Etymology. Deceptorius (Lat., adj.) - deceptive, in reference to small mor- phological differences from the closely related species. Description. Basidiocarps effused, smooth, first pruinose-reticulate, waxy, semitranslucent, greyish, then continuous, gelatinised, up to 1 cm in widest dimension, 0.03-0.07 mm thick, margin concolourous with hymenium, grad- ually thinning-out; tiny white spots often present in mature basidiocarps, irreg- ularly distributed on hymenial surface. Hyphal structure monomitic; hyphae clamped, subicular hyphae with a distinct wall, subparallel, 2-3 um in diam., subhymenial hyphae thin-walled or with a distinct wall, interwoven or ascend- ing, 1.5-2.5 um in diam., glued together. Tramal cystidia abundant, hyaline or brownish, tubular-clavate, usually tapering but sometimes slightly widened at the apex, arising from thin- or moderately thick-walled hyphae, with thickened (up to 3 um) walls gradually thinning-out towards the apical part (thin-walled apical parts often collapsing), (45—) 46-124 (-127) x (5.2—-) 5.3-11.3 (-11.8) um (n = 134/7), single or in groups of 2-5, occasionally biradicate, sometimes tortuous; hymenial cystidia hyaline, broadly clavate to subglobose, thin-walled, quickly collapsing, 12-26 x 5.2-12.4 um, scattered among basidia. Hyphidia present, simple or sparsely branched, 1-1.5 um in diam. at the apex. Crystals occasionally present on hyphidia and cystidia, acicular or fused in stellate ag- glomerations. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedun- culate, (6.9-) 7.0-9.1 (—9.8) x (6.0-) 6.1-7.2 (—7.8) um (n = 21/2), tightly glued together, stalk distinct, up to 4 x 3 um, sterigmata up to 5 x 1.5-2 um. Basidio- spores smooth, thin-walled, ellipsoid to broadly cylindrical or cylindrical, more rarely lacrymoid, (4.6—) 4.8-6.8 (—7.2) x (3.0-) 3.1-4.7 (—4.9) um (n = 210/7), L=5.54-5.94, W = 3.59-4.11, Q’ = (1.2-) 1.3-1.8 (-1.9), Q = 1.44-1.63. Ecology and distribution. Europe (Slovenia — basidiocarps on wood; Estonia, Georgia, Portugal, and Romania — soil sequences), North America (USA, West Virginia — soil sequence) (see further remarks below); strongly rotten wood of deciduous trees (Fagus, Salix). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 379 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Remarks. Protomerulius deceptorius is introduced here as a close relative of P commotus and P madidus (Figs 1, 4). Morphologically, it is highly similar to P commotus and differs from it primarily in having shorter tramal and smaller hymenial cystidia. Moreover, basidiospores of P deceptorius are slightly wider than in P commotus, although this difference is merely statistical, and the signif- icant part of P deceptorius specimens have basidiospores of the same size as in P commotus. Mature basidiocarps of P deceptorius usually contain white miner- al inclusions (Fig. 6); they are absent in all P commotus specimens studied by us. In total, eleven specimens of P deceptorius are known to us, all collected in Slo- venia and all but one derived from rotten wood of Fagus sylvatica. However, DNA sequences obtained from forest soil and root tips indicate that the species seems to be widely distributed in Europe (Fig. 4). GenBank sequence MF665126 from West Virginia, USA, shows a 1 bp difference in the ITS2 region versus P. deceptorius from Europe. We consider it as an intraspecific variation and assign this sequence to P. deceptorius. It was obtained from root tips of trees in a montane forest dom- inated by Fagus grandifolia and Quercus spp. (Nelson 2017). Several other soil se- quences from GenBank and UNITE cluster with P deceptorius, although without statistical support (Fig. 4). These all originated from subtropical and tropical ar- eas (South America, Southeast Asia, and Oceania) and may well represent sister taxa of P deceptorius. On the other hand, their differences versus P deceptorius sequences from Europe and North America may reflect genetic variation within one widely distributed species. Some other Protomerulius species with a wide distribution range (e.g., P brachysporus, P minor, and P. subreflexus) demonstrate significant ITS variation within one species (Spirin et al. 2019c). Whatever the case may be, a definite conclusion can be reached only after sequencing the full-length ITS region and, desirably, additional genetic markers from physical P deceptorius s. lato specimens collected in subtropical and tropical areas. Discussion In the present paper, we describe sixteen new species of Auriculariales with stalked basidia. Additionally, the generic affiliation of eleven extant species was reassessed based on phylogenetic and/or morphological data. Of these newly described or reassessed taxa, only one, Elmericium alabastrinum, be- longs to the core group of Auriculariales, i.e. the family Auriculariaceae, where it clusters with other genera that have peculiar petiolate basidia (Elmerina and Protodaedalea). The remaining genera dealt with above do not show particu- larly close affinity to the Auriculariaceae or to each other. We therefore refrain from proposing any novel suprageneric reclassification of these genera, pend- ing denser taxon sampling and sequencing of additional genetic markers. In the case of the Protodontia—Gelacantha clade, new data will certainly facilitate a better understanding of generic limits in this group than we present here. In our earlier revision of the Auriculariales with sphaeropedunculate basid- ia, five monotypic genera were introduced to accommodate taxa morphologi- cally highly similar to Myxarium but phylogenetically isolated from it (Spirin et al. 2019b, c). In this paper, we add new species to the previously monotypic Hydrophana, Mycostilla, and Protoacia. However, the discovery of these so far unknown species in these recently established genera has posed another prob- lem. Namely, expanding these genera has blurred their distinctions from other MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 380 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia morphologically similar but phylogenetically distant genera, which were origi- nally emphasised as unique. For example, the monotypic genus Mycostilla was originally distinguished from all other genera of the myxarioid Auriculariales (except Stypellopsis Spirin & Malysheva) by its giant, thin-walled cystidia. The introduction of another Mycostilla species, M. chromatica, which lacks cystidia entirely, makes it impossible to maintain the original concept of the genus. We show that the presence of sphaeropedunculate basidia alone is no lon- ger sufficient to determine the generic affiliation of a given species. Spirin et al. (2019b) demonstrated that Microsebacina fugacissima (Bourdot & Galzin) P. Roberts, a species with strictly sessile basidia, belongs to the genus Myxari- um, which is otherwise represented by taxa with stalked basidia. The genus Pro- tohydnum, as amended above, includes approximately the same number of spe- cies with stalked and sessile basidia. Further exploration of the diversity of the myxarioid Auriculariales will likely render the situation even more complicated. Nevertheless, we still believe that, in most cases, morphological definition of a genus is possible if based on a combination of morphological traits (cf. Spirin et al. 2024b). However, re-evaluation of taxonomically significant traits should be grounded in a densely sampled, multigene phylogeny of the corresponding suprageneric unit, i.e. a family or an order. Soil and environmental sequences provide another important source of infor- mation about species diversity and distribution within the group. At least one more Protoacia species related to P delicata and one more Myxarium species (potential- ly conspecific with M. inconspicuum, treated above) have been detected among unnamed GenBank sequences. Although basidiocarps of the newly described Protomerulius deceptorius have been collected only in Slovenia, available soil se- quences suggest a much wider distribution for this species in Europe and North America. Additionally, at least two more undescribed Protomerulius species are present among environmental data: one is a close relative of P madidus, distributed in North America, and another is a sister taxon of P minor from Argentina (Fig. 4). Recently, a few Protomerulius species have been shown to form symbiotic associations with several genera of orchids (McCormick et al. 2021; Suetsugu and Matsubayashi 2021). Thus, new data from mycorrhizal studies will likely expand our current knowledge of species diversity in Protomerulius spp. across different geographic regions, as well as their ecological roles and interactions with other organisms. Specimens examined (type specimens cited above are not listed) Bourdotia galzinii f. microcystidiata Hauerslev. France. Aveyron: Mélagues, Le Rec, Castanea sativa, 13.X1.1913 Galzin 14319 (herb. Bourdot 13956) (PC, holotype). Elmericium alabastrinum Spirin & V. Malysheva. Russia. Khabarovsk Reg.: Khabarovsk Dist., Malyi Niran, Acer mono, 7.VIII.2012 Spirin 5002 (H); Solnechnyi Dist., Suluk-Makit, Populus maximowiczii, 20.VIII.2011 Spirin 4226, 4227 (H). Endoperplexa dartmorica P. Roberts. Estonia. Viljandimaa: Tipu, Maasaare, Pinus sylvestris, 16.1X.2018 Spirin 12344* (H, TUF114815). Norway. Vest-Ag- der: Mandal, Ufgra, Picea abies, 2.X|.2017 Spirin 11781*, 11783%* (O, H). Sor-Tr@ndelag: Meldal, Urvatn, P abies, 27.1X.1991 Bendiksen & Hgiland 9-44 (O F149952). Sweden. Vastergotland: Tollsjd, rotten wood, 1.X.1969 Hjortstam 2784 (GB-0159286). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 381 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia Exidiopsis gloeophora (Oberw.) Wojewoda. Norway. Nord-Tréndelag: Snasa, Blafjella, P abies, 28.1X.2011 J. Nordén 9609% (0). Exidiopsis succinea K. Wells & Raitviir. Canada. British Columbia: Mc Leod Dist., road 44, Populus sp., 25.V1.1969 Eriksson 12078 (GB-0185809). Russia. Khabarovsk Reg.: Verkhnebureinsky Dist., Sidorka, Salix schwerinii, 24.VIII.2014 Spirin 7958* (H). Krasnoyarsk Reg.: Yenisseysk Dist., Yartsevo, Salix fragilis, 10.VIII.1958 Par- masto (TAAM 7008, holotype). Leningrad Reg.: Boksitogorsk Dist., Radogosch’, Salix cinerea, 26.1X.2012 Spirin 5836* (H). Sweden. Vastergdtland: Medelplana, Munkangarna, Ulmus glabra, 19.XII.2024 Spirin 18015 (GB). Torne Lappmark: Abis- ko Nat. Park, Salix sp., 8.VIII.1981 Hallenberg 3734 (GB-0185320). Hydrophana sphaerospora (Bourdot & Galzin) Malysheva & Spirin. Swe- den. Dalarna: Malung, Lybergsgnupen, Betula sp. (?), 23.VIII.2024 Sivula (GB). Halland: Sard, Quercus robur, 12.X.2024 Spirin 17677 (GB). Vastergdtland: Goteborg, Anggarden, U. glabra, 3.X.2024 Spirin 17632 (GB). Mycostilla chromatica Spirin & Grebenc. Slovenia. Kocevje: Podstenice, Ra- jhenavski Rog, Abies alba (fallen log), 30.VII.2020 Spirin 14013 (H). Mycostilla vermiformis (Berk. & Broome) Spirin & Malysheva. France. Avey- ron: Millau, Le Causse Noir, Pinus nigra, 8.V.2022 Spirin 15335* (H). Nether- lands. Drenthe: Dwingeloo, Lheebroekerzand, Reigerplas, Juniperus commu- nis, 1.VI.1970 de Vries 631 (GB-0185457). Romania. Brasov: Sinca, A. alba, 14.1X.2021 Spirin 14917, 14946, 14948 (H). Slovenia. Radovljica: Lipanca, Larix decidua, 26.1X.2019 Spirin 13270 (H). Sweden. Bohuslan: Resterdd, Ulvesund, P abies, 14.X.2023 Spirin 16921 (GB). United Kingdom. England: Somerset, Bathford Plantation, dead wood, 1.1V.1877 Broome 404 (K(M) 47312, holotype of Dacrymyces vermiformis). Myxarium cinnamomescens (Raitv.) Raitv. Austria. Niederésterreich: Perch- toldsdorf, Naturpark Fohrenberge, Tilia cordata, 10.1X.2022 Spirin 15784 (H). France. Essonne: Soisy-sur-Seine, Forét de Sénart, T. cordata, 11.X1.2021 Spi- rin 15272 (H). Russia. Sakhalin Reg.: Kunashir, Betula sp., 17.VIII.2017 Bulakh (LE F-347687*). Sweden. Bohuslan: H6n6, Ersdalsvagen, Populus tremula, 15.VII.2024 Spirin 17307 (GB). Vastergotland: Goteborg, Guldheden, P. trem- ula, 16.XII.2024 Spirin 17999 (GB); Hjalmsdater, Saten, P. tremula, 19.X1I.2024 Spirin 18014 (GB); Partille, Tultered, P tremula, 3.X1.2024 Spirin 17782, 17784 (GB); Vanersborg, Hunneberg, T. cordata, 15.X.2024 Spirin 17698 (GB); Vrang6, Vrangoskargarden, P. tremula, 15.X|.2024 Spirin 17987, 17990 (GB). Myxarium crozalcii (Bourdot & Galzin) Spirin & Malysheva. France. Aveyron: Millau, Le Causse Noir, Quercus pubescens, 21.11.2025 Spirin 18033 (H). Swe- den. Skane: Torekov, Hallands Vader6, Fagus sylvatica, 25-27.X.1975 Hallen- berg 1197 (GB-0185739). Smaland: Varnamo, Aminne, F. sylvatica, 17.X.2024 Spirin 17758 (GB). Vastergdtland: Gotene, Vasterplana Storang, U. glabra, 28.VIII.2024 Spirin 17510 (GB). Myxarium crystallinum D.A. Reid. Finland. Uusimaa: Helsinki, Oulunky- la, Verajalaakso, Acer platanoides, 17.X.2019 Viner 2023/26* (H). Norway. S¢r-Tréndelag: Kongsvoll, Varstigen, Betula tortuosa, 24.VIII.1979 Hjorts- tam 10447 (GB-0185788). Sweden. Smaland: Varnamo, Rusarebo, U. glabra, 17.X.2024 Spirin 17736 (GB). Myxarium evanidum Spirin & K.H. Larss. Finland. Varsinais-Suomi: Raase- pori, Ramsholmen, U. glabra, 6.X1.2021 Spirin 15193* (H). Sweden. Smaland: Varnamo, Aminne, F. sylvatica, 17.X.2024 Spirin 17761* (GB). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 389 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia Myxarium fugacissimum (Bourdot & Galzin) Malysheva & Spirin. Finland. Uu- simaa: Helsinki, Ostersundom, Stora Dammen, A. platanoides, 31.X.2022 Spi- rin 16085 (H). France. Aveyron: Millau, UHospitalet-du-Larzac, Q. pubescens, 8.X1.2024 Spirin 17971* (H). Myxarium grilletii (Boud.) D.A. Reid. France. Aveyron: Millau, Creissels, Acer pseudoplatanus, 16.X|.2022 Spirin 16479* (H). Sweden. Smaland: Hdgsby, Langemala, Getebro, F. sylvatica, 27.1X.2024 Spirin 17598 (GB). Vastergotland: Goteborg, Anggarden, U. glabra, 7.VII.2024 Spirin 17256, 17265 (GB), 9.VII.2024 Spirin 17271 (GB); Gotene, Vasterplana Storang, Q. robur, 28.VIII.2024 Spi- rin 17514 (GB), U. glabra, 28.VIII.2024 Spirin 17511 (GB); Hallekis, Tornsater, U. glabra, 28.VIII.2024 Spirin 17520, 17526, 17528 (GB); Partille, Tultered, P tremula, 3.X|1.2024 Spirin 17776 (GB); Vanersborg, Vastra Tunhem, Q. robur, 15.X.2024 Spirin 17712, 17714 (GB). Bohuslan: H6n6, Ersdalsvagen, P. tremula, 12.VIII.2024 Spirin 17366 (GB); Mjérn, Sundsby, Corylus avellana, 7.1X.2024 Spi- rin 17536, 17538, 17540 (GB), F. sylvatica, 7.1X.2024 Spirin 17531 (GB). Myxarium hyalinum (Pers.) Donk. Austria. Niederésterreich: Perchtoldsdorf, Naturpark Fohrenberge, F. sylvatica, 10.1X.2022 Spirin 15772 (H). France. Avey- ron: Millau, Creissels, A. pseudoplatanus, 16.X|.2022 Spirin 16482 (H). Sweden. Vastergotland: Géteborg, Anggarden, U. glabra, 7.VII.2024 Spirin 17264 (in- fected by Zygogloea gemellipara P. Roberts) (GB); Vrang6, Vrangoskargarden, P tremula, 15.X1.2024 Spirin 17995 (GB). Bohuslan: H6n6, Ersdalsvagen, Cytis- us scoparius, 12.X|.2023 Spirin 17040, 17044* (GB); Okeré, Hals6, Betula pubes- cens, Hippophae rhamnoides, 11.VII.2024 Spirin 17282, 17284 (GB). Myxarium legonii (P. Roberts) P. Roberts. France. Aveyron: Millau, Dourbie, Fraxinus excelsior, 15.X1.2022 Spirin 16337 (H), Ravin de Potensac, Populus nigra (rotten log), 15.X1.2022 Spirin 16419* (H). Spain. Navarra: Sarasibar, rot- ten wood, 9.XI.2020 Garcia (H). United Kingdom. England: Surrey, Runnymede, Cooper’s Hill, Ulmus sp., 30.VI.1988 Legon (TAAM 132119). Myxarium mesomorphum (Bourdot & Galzin) Hauerslev ex Spirin, Malysheva, P. Roberts, Trichies, A. Savchenko & K.H. Larss. France. Aveyron: Millau, Dour- bie, F. excelsior, 23.11.2025 Spirin 18159 (H). Sweden. Vasterg6tland: MolIndal, Solangen, Sndhdjdsliden, Thymus sp. (cultivated), 5.11.2024 Spirin 17047 (GB); Vanersborg, Vastra Tunhem, Q. robur, 15.X.2024 Spirin 17717 (GB); Vrang6, Vrangoskargarden, C. avellana, 15.X1.2024 Spirin 17993 (GB). Myxarium minutissimum (Hohn.) Spirin & Trichies. Austria. Niederésterreich: Perchtoldsdorf, Naturpark Fohrenberge, F. sylvatica, 10.1X.2022 Spirin 15780 (H). Denmark. Jylland: Mols Bjerge, Strandkjaer, J. communis (?), 25.VII.1981 Hallenberg 3501 (GB-0185500). Finland. Uusimaa: Helsinki, Vuosaari, Broanda, S. caprea, 4.X1.2022 Spirin 16127 (H). Norway. Rogaland: Hogganvik, F. sylvatica, 2.VIII.1984 Hallenberg 8377 (GB-0185497): Ropeid, Q. robur, 3.VIII.1984 Hallen- berg 8383 (GB-0185498). Slovenia. Postojna: Drskovée, C. avellana, 29.1X.2023 Spirin 16810 (H); Sezana: Divaéa, Q. pubescens, 27.1X.2023 Spirin 16683* (H). Sweden. Smaland: Hégsby, Langemala, Bokhultet, Q. robur, 24.1X.2024 Spirin 17555 (GB), Danmarksvagen, F. sylvatica, 27.IX.2024 Spirin 17621 (GB), Getebro, F. sylvatica, 27.1X.2024 Spirin 17603, 17607, 17611 (GB); Varnamo, Rusarebo, A. platanoides, 17.X.2024 Spirin 17733 (GB). Vastergotland: Halanda, Holme- vattnet, deciduous wood, 3.1X.1970 Hjortstam 3402 (GB-0185731); Goteborg, Anggarden, T. cordata, 7.VII.2024 Spirin 17258 (GB), U. glabra, 9.VII.2024 Spi- rin 17270* (GB); Medelplana, Munkangarna, U. glabra, 15.X.2023 Spirin 16947 MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 393 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia (GB); Partille, Tultered, P. tremula, 3.X1.2024 Spirin 17773 (GB). Bohuslan: H6n6, Ersdalsvagen, C. scoparius, 15.VII.2024 Spirin 17325 (GB); Oker6, Hals6, Q. ro- bur, 11.VII.2024 Spirin 17303 (GB). Myxarium nucleatum Wallr. Austria. Niederdosterreich: Perchtoldsdorf, Natur- park Fohrenberge, F. excelsior, 10.1X.2022 Spirin 15781 (H). France. Aveyron: Millau, Creissels, F. excelsior, 16.X1.2022 Spirin 16494 (H). Sweden. Vasterg6t- land: Partille, Tultered, P tremula, 3.X1.2024 Spirin 17774 (GB). Myxarium podlachicum (Bres.) Raitv. Austria. Niederdsterreich: Perchtolds- dorf, Naturpark Fohrenberge, C. avellana, 10.1X.2022 Spirin 15795, 15796 (H), F. sylvatica, 10.1X.2022 Spirin 15778 (H). Finland. Varsinais-Suomi: Raasepori, Ramsholmen, U. glabra, 6.X1.2021 Spirin 15194 (H). Sweden. Halland: Saré, B. pubescens, 12.X.2024 Spirin 17670 (GB). Smaland: Hégsby, Langemala, Barnebo, U.glabra, 23.1X.2023 Spirin 17552 (GB), Langemala, Getebro, F. syl- vatica, 27.1X.2024 Spirin 17609 (GB), Bokhultet, F sylvatica, 24.1X.2024 Spirin 17557 (GB); Varnamo, Rusarebo, A. platanoides, 17.X.2024 Spirin 17722 (GB), Aminne, F. sylvatica, 17.X.2024 Spirin 17755 (GB). Vastergétland: Goteborg, Anggarden, Alnus glutinosa, 7.VII.2024 Spirin 17251 (GB), U. glabra, 7.VII.2024 Spirin 17261 (GB), 9.VII.2024 Spirin 17273 (GB); Medelplana, Munkangarna, U. glabra, 15.X.2023 Spirin 16934, 16945 (GB); Vanersborg, Hunneberg, C. avel- lana, 15.X.2024 Spirin 17694 (GB), Vastra Tunhem, Q. robur, 15.X.2024 Spirin 17720 (GB); Vrang6, Vrangdéskargarden, Sorbus sp., C. avellana, 19.VII.2024 Spirin 17335, 17337 (GB), Tarnstigen, Q. robur, 19.VII.2024 Spirin 17344, 17345 (GB). Bohuslan: H6n6, Ersdalsvagen, P. tremula, 15.VII.2024 Spirin 17305 (GB); Ljungskile, Bratteforsan, U. glabra, 17.VIII.2023 Spirin 16589* (GB); Mj6rn, Sundsby, F. sylvatica, Q. robur, 7.1X.2024 Spirin 17534, 17542 (GB). Myxarium populinum (P. Karst.) Spirin & Malysheva. Sweden. Dalarna: Malung, Botaberget, P tremula, 25.VIII.2024 Spirin 17502 (GB). Vastergotland: Partille, Tultered, P. tremula, 3.X1.2024 Spirin 17779, 17783 (GB). Myxarium spiniferum Spirin & V. Malysheva. USA. New York: Essex Co., Arbu- tus Lake, decayed wood, 17.VIII.2012 Miettinen 15677* (H). Tennessee: Sevier Co., Ramsey Cascades Trail, decayed wood, 13.VII.2004 Larsson 12177 (GB). Myxarium varium Hauerslev. France. Aveyron: Millau, LHospitalet-du-Larzac, Q. pubescens, 7.X|.2024 Spirin 17908 (H). Lozére: Saint-Etienne-du-Valdonnez, Forét du Sapet, F. sylvatica, 28.V1.2022 Spirin 15558, 15560 (H), 29.V1.2022 Spi- rin 15646*, 15649 (H). Slovenia. llirska Bistrica: Sneznik, F. sylvatica, 28.1X.2023 Spirin 16770 (H). Sweden. Vastergétland: Asklanda, Kvinnestad, deciduous branches, 6.X.1970 Hjortstam 5130 (GB-0185733); Vrang6, Vrangoskargarden, P tremula, 19.VII.2024 Spirin 17332 (GB), Tarnstigen, Q. robur, 19.VII.2024 Spi- rin 17343 (GB). Bohuslan: H6n6, Ersdalsvagen, C. scoparius, 15.VII.2024 Spirin 17313 (GB); Save, Lindesnds, C. avellana, 1.Xl.1973 Eriksson (GB-0185755). Oliveonia fibrillosa. USA. Washington: Jefferson Co., Morgan's Crossing, Acer macrophyllum, 7.X.2014 Spirin 8257* (H). Protoacia delicata Spirin & Malysheva. Finland. Inarin Lappi: Inari, Kuusipaa, P abies, 9.1X.1962 Strid & Eriksson 10143 (GB-0185568). Sompion Lappi: Pelkosenniemi, Iso Palovaara, P abies, 5.1X.2020 Spirin 14172, 14180, 14182 (H). Norway. Nord-Tr@ndelag: Stjgrdal, Nyvollkjglen, on wood in Picea forest, 15.1X.1983 Hallingback (GB-0185559). Russia. Nizhny Novgorod Reg.: Sharanga Dist., Kilemary, P abies, 24.VIII.2019 Spirin 13010* (H). Sweden. Smaland: Varna- mo, Bjors, P. abies, 26.VIII.1959 Eriksson 3925 (GB-0185749), 16.X.1960 Eriksson MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 384 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia 3950 (GB-0185748). Vastergotland: Ostad, Faglaryd, P. sylvestris, 4.1X.1970 Hjort- stam 3491 (GB-0185732). Dalarna: Alvdalen, Rédberget, P. abies, 19.VIII.2024 Spirin 17383 (GB); Transrand, Bredvallen, P. abies, 22.VIII.2024 Spirin 17445 (GB); Garpenberg, decayed trunk, 29.VIII.1974 Hallenberg 19 (GB-0185628). Jamtland: Revsund, Stavre, P. sylvestris, 30.VII.1958 Eriksson 8288 (GB-0185783). Asele Lappmark: Asele, Rédberget, P. abies, 28.VIII.2023 Spirin 16601 (GB). Protodontia subgelatinosa (P. Karst.) Pilat. Russia. Nizhny Novgorod Reg.: Lukoyanov Dist., Panzelka, T. cordata, 1.VIII.2019 Spirin 12797 (H). Sweden. Vastergotland: Gdteborg, Anggarden, A. glutinosa, 3.X.2024 Spirin 17626 (GB). Protohydnum album (Lloyd) Spirin. USA. Arkansas: Marion Co., Buffalo Point, angiosperm, 26.X.2013 Miettinen 17498 (H). Illinois: McLean Co., Funk’s Grove, hardwood, 13.VIlI.1965 Cain (LE 37320* ex TRTC). Indiana: Montgomery Co., Crawfordsville, dead logs, 5.X1.1922 Bechtel 5, 6 (BPI 719951, 719953). lowa: Tama Co., Tama, 30.VI.1928 Shimek (BPI 719954). Minnesota: Waseca Co., Janesville, Willis Lake, Acer saccharum, 21.VIII.2013 Miettinen 16734.1 (H). Missouri: St. Louis Co., Allenton, Platanus sp. (?), 8.1X.1929 Linder (BPI 719949). Nebraska: [no locality indicated], old logs, VII.1887 Webber (BPI 719948). New York: Ontario Co., Farmington, VIII.1889 Brown (BPI 719952). Tennessee: Sevi- er Co., Ramsey Cascade trail, Tilia americana, 30.1X.2015 Miettinen 19583* (H). Protohydnum cartilagineum Moller. Brazil. Santa Catarina: Blumenau, 1891 Moller 106 (HBG), [no collecting date] Moller 19, 20 (HBG). Sao Paulo: Iguape, Jureia-Itatins, Rio Verde, fallen trunk, 28.V1.2017 Pires 406% (H). Protohydnum gaizinii (Bres.) Spirin & R.H. Nilsson. Austria. Niederdster- reich: Perchtoldsdorf, Naturpark Fohrenberge, F. excelsior, 10.1X.2022 Spirin 15803 (H). France. Alpes-Maritimes: Cannes, Ile de Saint-Marguerite, Quercus ilex, 12.X1.2022 Gruhn 221112-005, 221112-007 (G.G., H), unidentified an- giosperm wood, 12.XI.2022 Gruhn 221112-013 (G.G., H). Aveyron: Combret, Bétirac, P nigra, 21.1I|.2024 Spirin 17091 (H), F excelsior, 6.X1.2024 Spirin 17818 (H, GB). Dréme: Montélimar, Platanus orientalis, 11.X1.1966 Lanquetin (LY JB-5742). Landes: Port-de-Lanne, A. glutinosa, 17.1I1.1985 Gilles 486 (LY JB-10973). Pyrénées-Atlantiques: Pardies, rotten wood, 22.11.1964 Beller (LY JB-4761); Sauveterre-de-Béarn, P. nigra, 26.11.1983 Gilles 045 (LY JB-10128), 29.111.1985 Gilles (LY JB-11893). Isére: Veyrins-Thuellin, Les Aveniéres, P. nig- ra, 29.1I1.2012 Rivoire (LY BR4339, H). Rhéne: Millery, Hedera helix, 29.1V.2014 Rivoire (LY BR5393). Iran. Mazanderan: Jangale, fallen branch, 11.VII.1976 Hallenberg 1674 (GB-0185314), fallen decayed branch, 12.VII.1976 Hallen- berg 1729 (GB-0185313). Italy. Veneto: Venice, Carpenedo, deciduous wood, 1.V.1992 Losi (GB-0078123). Russia. Krasnodar Reg.: Khosta, Acun, fallen angiosperm log, 17.1X.1996 Hallenberg 13135 (GB-0184376). Spain. Canary Ids.: La Palma, Puntallana, angiosperm wood, 25.VII.2022 Viner 2022/1023* (H). Malaga: Mijas, Los Espartales, ona living tree (Cupressaceae), 20.X1.2012 Miettinen 15900.4* (H). Ukraine. Lugansk Reg.: Stanichno-Luganskii Dist., Severnyi Donets, Populus alba, 20.X.2010 Akulov (CWU 4564*). Protohydnum lactescens (Burt) Spirin & V. Malysheva. USA. California: Napa Co., St. Helena, on wood, 29.XII.1960 Wells* (TAAM192048), Sage Creek, on wood, 8.XII.1962 Wells & Prusso (TAAM192047). Protohydnum livescens (Bres.) Spirin & V. Malysheva. Austria. Niederds- terreich: Perchtoldsdorf, Naturpark Fohrenberge, Pinus nigra, 10.1X.2022 Spirin 15807, 15810 (H). France. Aveyron: Millau, Le Causse Noir, P. nigra, MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 395 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 21.11.2025 Spirin 18076 (H), Le Pas Destrech, P. nigra, 7.X|.2024 Spirin 17873 (H). Lozére: Saint-Etienne-du-Valdonnez, Forét du Sapet, A. alba, 28.V1.2022 Spirin 15514, 15530 (H), 29.VI.2022 Spirin 15619, 15622 (H). Rhdne: St. Laurent d’Agny, Bois Bouchat, P. sylvestris, 8.XII.2020 Rivoire 7684 (LY). Greece. Central Athens: Kaisariani, Asteriou, Pinus halepensis, 10.1.2022 Viner 2022/7* (H). Romania. Brasov: Prund-Schei, A. alba, 20.V.2017 Miet- tinen 20660* (H). Slovenia. Gorenjska: Ravne v Bohinju, A. alba, 28.VII.2020 Spirin 13886, 13913* (H). KoGevje: Podstenice, Rajhenavski Rog, A. alba, 19.VIII.2021 Spirin 14774 (H). Spain. Andalusia: Malaga, Mijas, P- halepen- sis, 16.X1.2012 Miettinen 15891.1* (H), Pinus pinaster, 16.X1.2012 Miettinen 15872.2* (H), 24.X1.2012 Miettinen 16000* (H). Ukraine. Zakarpats’ka Reg.: Kuzy, A. alba, VIII.1934 Pilat (H ex Fungi Carpatici Lignicoli Exsiccati #152). Protohydnum nudum Spirin & Ryvarden. Kenya. Western Province: Kakamega Forest, decayed wood, 25-27.1.1973 Ryvarden 9457 (0, H). Protohydnum pululahuanum (Pat.) Spirin. Ecuador. Pichincha: Quito, Pululahua, decayed wood, [no collecting date] Lagerheim (FH00783538, 00783539, 00783540). Protohydnum sucinum (Moller) Spirin & Alvarenga. Brazil. [no locality and collecting date], Rick (Lloyd’s herbarium #38807, 33209, as Auricularia brasil- iensis) (BPI701264, 701268). Protohydnum sp. French Guiana. Regina: Chute de Patawa, hardwood, 31.VIII.2018 Viasak 1808/145* (H). Protomerulius amiliavi Spirin. France. Aveyron: Millau, Le Causse Noir, Q. pu- bescens, 21.11.2025 Spirin 18037 (H). Protomerulius brachysporus (Luck-Allen) Spirin & Malysheva. Canada. Brit- ish Columbia: Vancouver Island, between Cowichan and Port Renfrew, dead wood, 12.VIlII.1988 Hallenberg 10651 (GB-0185453). France. Aveyron: Millau, Larzac, Le Rajal del Gorp, P. sylvestris, 14.X1.2022 Spirin 16282, 16285, 16288* (H), UHospitalet-du-Larzac, J. communis, 8.X|.2024 Spirin 17963 (H). Slove- nia. Kocevje: Podstenice, Rajhenavski Rog, A. a/ba, 19.VIII.2021 Spirin 14820 (H). Sweden. Gothland: Uppsteig, P abies, 21.X.1984 Hallenberg 8719 (GB- 0185439). Uppland: Lundsvedja, strongly rotten wood, 12.VI.1952 Eriksson 6646 (GB-0185443). Vastergétland: Medelplana, P abies, 8.X.2008 Larsson 13891 (GB-0087471). Vasterbotten: Holmsund, Obbola, P. abies, 1.X.1970 Strid 7899 (GB-0185444). Ostergétland: Vaversunda, Omberg, Abies sp., 30.X.1978 Hallingback (GB-0185442). USA. California: San Bernardino Nat. Forest, San Jacinto Mts., conifer, 17.1II.1984 Ryvarden 21748 (GB-0185452). Protomerulius commotus Spirin & V. Malysheva. France. Aveyron: Castel- nau-Pégayrols, Le Trou d’Enfer, Q. pubescens, 22.1I|.2024 Spirin 17127* (H). It- aly. Liguria: Imperia, Pigna, Buggio, Carpinus betulus, 17.X.2019 Spirin 13835* (H). Norway. Vestfold: Larvik, Jordstayp i Kvelde, U. glabra, 15.1X.2016 Spirin 11110%* (O). Switzerland. Ticino: Sementina, Boschetti, F excelsior, 13.X.2019 Spirin 13617* (H). Sweden. Vasterg6tland: Hallekis, Tornsater Nat. Res., U. gla- bra, 5.X.2024 Spirin 17657 (GB). Protomerulius deceptorius Spirin & Viner. Slovenia. Cerknica: Goricice, S. caprea, 30.1X.2023 Spirin 16863%* (H). llirska Bistrica: SneZnik, F. sylvatica, 17.VIII.2021 Spirin 14634, 14592*, 14651*, 14652 (H), 28.1X.2023 Spirin 16764*, 16773, 16784, 16788 (H). Kocevje: Borovec pri Kocevski Reki, Krokar Forest Re- serve, F. sylvatica, 18.VIII.2021 Spirin 14659 (H). MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 386 Viacheslav Spirin et al.: Auriculariales with pedunculate basidia Protomerulius dubius (Bourdot & Galzin) Spirin & Malysheva. Finland. Uu- simaa: Helsinki, Verajamaki, Pirunkallio, Salix sp., 22.X.2019 Viner 2019/154* (H). Sweden. Oland: Hégsrum, Q. robur (rotten log), 18.X.1990 B. Nordén (GB). Protomerulius madidus Spirin & K.H. Larss. France. Aveyron: Saint-Sernin- sur-Rance, Le Bouissou, Q. pubescens, 6.X1.2024 Spirin 17851* (H). Roma- nia. Brasov: Sinca, F. sylvatica, 14.1X.2021 Spirin 14943 (H). Arad: Barza- va, Runcu-Grosi, F. sylvatica, 15.1X.2021 Spirin 15021* (H). Russia. Nizhny Novgorod Reg.: Lukoyanov Dist., Razino, P tremula, 27.VII.2019 Spirin 12699 (H), U. glabra, 28.VII.2019 Spirin 12724 (H), Sanki, Ulmus laevis, 31.VIII.2019 Spirin 13076 (H), Q. robur, 31.VII.2021 Spirin 14455 (H). Sweden. Vastergot- land: Hallekis, Tornsdter Nat. Res., C. avellana, 5.X.2024 Spirin 17651 (GB). Medelplana, Munkagarna, C. avellana, 15.X.2023 Spirin 16931 (GB), U. gla- bra, 15.X.2023 Spirin 16926, 16940, 16951*, 16953 (GB). Vastmanland: Rytterne, Kalvholmen, Salix sp., 28.X.1981 Hallingback (GB-0185454). Up- pland: Uppsala, Vardsatra, angiosperm wood, 19.X.1967 Sunhede & Eriks- son (GB-0185455). Gastrikland: Gavle, L6vudden, Betula sp., 4.VIII.1957 Nannfeldt 15318 (GB-0185456). Protomerulius pertusus Malysheva & Spirin. Belgium. Antwerp: Wilrijk, Fort 7, deciduous log, 2000 De Meulder (GB-0185448). Norway. S@r-Tréndelag: Trond- heim, Almelia, U. glabra, 28.VIII.1982 Hjortstam 12902 (GB-0185446). Russia. Ady- gea: Maykop Dist., Guzeripl, F. sylvatica, 17.1X.2003 Kotiranta 22589* (H). Nizhny Novgorod Reg.: Lukoyanov Dist., Razino, U. glabra, 28.VII.2019 Spirin 12743* (H). Acknowledgements The curators of herbaria S, LE, FH, PC, K, BPI, NY, HBG, LY, TAAM, CWU, and TUF are thanked for providing specimens on loan. Author AS thanks Paul Kirika for handling specimens at the Nairobi National Museum (Kenya); his visit to Kenya was funded by a University of Helsinki Chancellor’s grant. Otto Miettinen (Uni- versity of Helsinki, Finland) kindly shared his collections and data with us. Additional information Conflict of interest The authors have declared that no competing interests exist. Ethical statement No ethical statement was reported. Use of Al No use of Al was reported. Funding The study was supported by the Artdatabanken project 2022.4.3-14 (author VS), the Research Council of Finland project 364105 (authors VS and IV), the Komarov Botani- cal Institute RAS project No. 12401310-0829-3 (author VM), the U.S. National Science Foundation grant DEB-2030779 (author DG, awarded to P. Brandon Matheny), the Con- selho Nacional de Desenvolvimento Cientifico e Tecnolédgico (CNPq 307601/2015-3), the Coordenagao de Aperfeigoamento de Pessoal de Nivel Superior (CAPES Capes-SIU MycoKeys 120: 339-392 (2025), DOI: 10.3897/mycokeys.120.155492 387 Viacheslav Spirin et al.: Auricu/ariales with pedunculate basidia 008/13), the Fundagao de Amparo de Ciéncia e Tecnologia do Estado de Pernambuco (FACEPE APQ0375-2.03/1) (author RLMA), and by institutional support from the Acad- emy of Sciences of the Czech Republic (RVO: 60077344) (author JV). Fieldwork in Gui- ana (author GG) was supported by UMS PatriNat, MIGBio, the Ministry of Environment (MTEECR), and the Office National des Foréts (DFRN), France. Author contributions Viacheslav Spirin - collecting specimens, microscopy, type studies, writing the first man- uscript draft. Vera Malysheva - sequencing specimens, illustration work. Ilya Viner - se- quencing specimens, illustration work. Renato Lucio Mendes Alvarenga, Tine Grebenc, Gérald Gruhn, Anton Savchenko, Django Grootmyers, Leif Ryvarden, Josef Vlasak, Karl-Henrik Larsson - collecting and sequencing specimens, manuscript writing. R. Hen- rik Nilsson - phylogenetic analyses, manuscript writing. Author ORCIDs Renato Lucio Mendes Alvarenga ® https://orcid.org/0000-0003-0400-3762 Tine Grebenc ® https://orcid.org/0000-0003-4035-8587 Gérald Gruhn ® https://orcid.org/0000-0003-4829-4960 Anton Savchenko ® hitps://orcid.org/0000-0001-6377-6349 Django Grootmyers © https://orcid.org/0000-0002-1042-4902 Josef Vlasak © https://orcid.org/0000-0002-5363-4459 Karl-Henrik Larsson © https://orcid.org/0000-0002-1248-3674 R. Henrik Nilsson © https://orcid.org/0000-0002-8052-0107 Data availability All of the data that support the findings of this study are available in the main text. References Bandoni RJ (1984) The Tremellales and Auriculariales: An alternative classification. Nip- pon Kingakkai Kaiho 25: 489-530. Bourdot H, Galzin A (1924) Heterobasidiae nondum descriptae. Bulletin de la Société Mycologique de France 39: 261-266. Bresadola G (1898). Fungi Tridentini 2(11-13): 47-81. https://doi.org/10.1086/472205 Bresadola G (1908) Fungi aliquot Gallici novi vel minus cogniti. 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