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Based on molecular phylogenetic analyses, and also considering morphological characters, four new families are separated from the family Glomeraceae within the order Glomerales and the class Glomeromycetes. The revised family Glomeraceae comprises only four genera: the type genus Glomus, Complexispora, Sclerocarpum and Simiglomus. Septoglomeraceae fam. nov. comprises, besides Septoglomus, Funneliformis, Funneliglomus, Blaszkowskia and Viscospora. Sclerocystaceae fam. nov. is represented by the type genus Sclerocystis but also by Halonatospora, Oehlia, Parvocarpum, Rhizoglomus and Silvaspora. Kamienskiaceae fam. nov. encompasses Kamienskia, Microkamienskia and Epigeocarpum. Finally, Dominikiaceae fam. nov. includes the genera Dominikia, Macrodominikia gen. nov., Microdominikia, Nanoglomus and Orientoglomus. The genera Oehlia and Halonatospora form two other clades well separated from Silvaspora, Sclerocystis and Rhizoglomus and might represent two further families within Glomerales. This deeper separation is, in our opinion, fully supported by molecular phylogeny, but in view of the low numbers of taxa, the separation is not yet proposed at this stage of research progress.

The objective of the present study was to revise the recently described order Entrophosporales of the Glomeromycetes. The single family Entrophosporaceae had been divided into three genera, Entrophospora, Claroideoglomus and Albahypha, due to molecular phylogenetic or morphological analyses, but recently these three genera were combined within the type genus of the family, Entrophospora. Our new studies now suggest once more three genera, but Entrophospora and Claroideoglomus were not separated again. In the present study, we resurrected Albahypha with A. drummondii and A. furrazolae comb. nov. and established Alborhynchus gen. nov. with A. walkeri comb. nov. Morphologically, all glomoid morphs of the three genera have hyaline to white subtending hyphae with one spore wall continuous with the subtending hyphal wall. However, the genera can easily be differentiated from each other and from other glomoid species of the Glomeromycetes by the combination of the characteristics of the subtending hyphae, the staining reaction of the spore wall layers in Melzer’s reagent and phylogeny. In conclusion, the three AMF genera, currently recognized in the Entrophosporales, can unequivocally be identified by molecular phylogeny or by morphological characteristics of their spores and their subtending hyphae. An identification key distinguishes all AMF species currently attributed to Entrophosporales.