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We report on the isolation and characterization of three isolates of anaerobic gut fungi from a cattle faecal sample obtained in Stillwater, OK, USA. The isolates produced polycentric thalli with nucleated rhizomycelia, lobed appressorium-like structures, intercalary sporangia and constricted sausage-like hyphae. These morphological features are characteristic of members of the genusAnaeromyces. No zoospore production was observed during the isolation process or thereafter. The strains seemed to have propagated solely through their nucleated hyphae post initial enrichment. Phylogenetic analysis of the D1/D2 region of the large ribosomal subunit (D1/D2 LSU) rRNA, the ribosomal intergenic spacer region 1 (ITS1), RNA polymerase II large subunit (RPB1) and comparative average amino acid identity using transcriptomic datasets further confirmed the position of the type strain as a distinct member of the genusAnaeromyces, familyAnaeromycetaceaeand phylumNeocallimastigomycota. We propose to accommodate these isolates into a new species (Anaeromyces corallioides) within the genusAnaeromyces. The type strain is EE.1. 

Abstract Despite their role in host nutrition, the anaerobic gut fungal (AGF) component of the herbivorous gut microbiome remains poorly characterized. Here, to examine global patterns and determinants of AGF diversity, we generate and analyze an amplicon dataset from 661 fecal samples from 34 mammalian species, 9 families, and 6 continents. We identify 56 novel genera, greatly expanding AGF diversity beyond current estimates (31 genera and candidate genera). Community structure analysis indicates that host phylogenetic affiliation, not domestication status and biogeography, shapes the community rather than. Fungal-host associations are stronger and more specific in hindgut fermenters than in foregut fermenters. Transcriptomics-enabled phylogenomic and molecular clock analyses of 52 strains from 14 genera indicate that most genera with preferences for hindgut hosts evolved earlier (44-58 Mya) than those with preferences for foregut hosts (22-32 Mya). Our results greatly expand the documented scope of AGF diversity and provide an ecologically and evolutionary-grounded model to explain the observed patterns of AGF diversity in extant animal hosts.