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.

Fomitiporia cupressicola sp. nov., found in living Cupressus arizonica, is described on the basis of several collections originating from a high altitude forest in the northern Sierra Madre Occidental, Mexico. The species forms a monophyletic clade, basal to a larger lineage comprising species originating mainly from temperate to Mediterranean areas of the northern hemisphere. The phylogenetic approach in Fomitiporia also revealed multiple unnamed clades within the F. robusta complex in the southern USA and northern Mexico, representing potential species. The status of the F. robusta complex in North America is discussed briefly.

Phylloporia rzedowskii and Phylloporia ulloai, both collected in tropical forests of the Sierra of the Huasteca Potosina, San Luis Potosi, Mexico, are described as new species. The main critical morphological features that characterize them are the pileus shape, the pore diameter, the basidiospores shape and size, and, possibly, their ecology, such as the host relationships (specificity/ preference). Both species also form distinct clades in phylogenetic analysis based on partial DNA sequences data from the nuclear ribosomal LSU. An identification key for 10 species reported from the Americas is proposed.

Six species of the genus Fomitiporia are described and illustrated for the first time from Mexico and they are F. apiahyna, F. calkinsii, F. dryophila, F. langloisii, F. maxonii y F. texana; F. sonorae is reported from Querétaro State. The specimens are deposited in the Herbaria CESUES, ENCB, FCME, IBUG, ITCV, MEXU, UJAT, UNL, UJED from Mexico and MUCL and proceed from 18 states of the Mexican Republic. Besides, a distribution map of the species is presented.

We report the identification of a fungus, a member of the genus Neoscytalidium which is associated with human keratitis. Phylogenetic analysis and morphological observations on conidiogenous cells, which occur only in arthric chains in aerial mycelium and the coelomycetous synasexual morph is absent, identified a new species, Neoscytalidium oculus sp. nov. The fungus formed biofilm at a concentration of 1 × 10 conidia/mL, during 96 hours of incubation at 37°C, and also manifested haemolysis and melanin production. This is the first report in Latin America of a new species of Neoscytalidium from a clinical isolate has been identified.