Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.

Descriptions and illustrations are provided for six diatrypaceous species from Iran. Diatrypella macrospora is introduced as new to science. It differs from all other Diatrypella species by its larger ascospores. New records for the Iranian mycota include Cryptovalsa rabenhorstii, Eutypella citricola, Peroneutypa scoparia and Quaternaria quaternata. Descriptions and illustrations of microscopic characters, ITS sequence data and taxonomic notes are provided for these newly reported taxa.

Two species of Diatrypaceae (Xylariales) are described and illustrate from Iran. Diatrypella iranensis from dead branches of Quercus brantii is described as a new species based on both morphology and molecular sequence data. It differs from other members of the genus on the basis of stroma morphology and ascus and ascospore sizes. Molecular data of the ITS rDNA region show that the new species is a sister taxon of Diatrypella quercina. Cryptovalsa ampelina is described from dead branches of Juglans regia and is a new record from Iran. This study is the first in a series that investigate the diversity of Diatrypaceae from Iran.

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We found one specimen of Dermea on dead branches of an unknown tree in Arasbaran forests of Iran in 2015. Based on phylogenetic analysis of combined ITS, LSU, SSU sequence data, as well as morphological observations, a new species of Dermea, D. persica, is described and illustrated here. This species, the only species of Dermea lacking a sexual morph, is mainly characterized by beaked pycnidia, hyaline to pale brown at the base and dark brown at the apex, opening by a circular ostiole, discrete or integrated conidiogenous cells with a minute periclinal wall thickening and falcate, aseptate conidia, 20–25(–30) × 2.5–3.5 µm, and lacking microconidia. The relatedness between D. persica and its close relatives is discussed. An updated key to Dermea species is also provided.