MYCOTAXON ISSN (print) 0093-4666 (online) 2154-8889 Mycotaxon, Ltd. ©2021 April–June 2021—Volume 136, pp. 373–385 https://doi.org/10.5248/136.373 Entyloma eranthidis sp. nov. on Eranthis longistipitata from Uzbekistan Teodor T. Denchev 1* , Cvetomir M. Denchev 1 , Martin Kemler 2 , Dominik Begerow 2 1 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin St., 1113 Sofa, Bulgaria 2 AG Geobotanik, Ruhr-Universität Bochum, ND 03, Universitätsstraße 150, 44801 Bochum, Germany * Correspondence to: ttdenchev@gmail.com Abstract—A new smut fungus, Entyloma eranthidis on Eranthis longistipitata from Uzbekistan, revealed by molecular, morphological, and ecological evidence, is described and illustrated. It difers from all other species of Entyloma by host specialization on Eranthis and by having longer (≤35(–38) µm) spores and thicker (≤10(–12) µm) spore walls. ITS rDNA sequence analysis indicates that the new species does not cluster with other species of Entyloma on Ranunculaceae. Key words—Entylomataceae, phylogeny, taxonomy Introduction Eranthis Salisb. (Ranunculaceae) is a small genus with a geographic range extending from southern Europe and Turkey to central and east Asia. It contains eleven species (Rukšāns & Zetterlund 2018, Park & al. 2019). Four are with yellow perianth-segments: E. hyemalis (L.) Salisb. (native to South Europe), E. cilicica Schott & Kotschy (in the Taurus Mts and Iranian and Iraq Kurdistan; considered by some authors conspecifc with previously named species; Davis & al. 1965, Tutin 1993), E. iranica Rukšāns & Zetterl. (from Iran), and E. longistipitata Regel (from central Asia) (Frizen 1993, Rukšāns & Zetterlund 2018, Park & al. 2019). Te remaining species produce white