Agaricales » Agaricales genera incertae sedis » Praearthromyces

Praearthromyces corneri

Praearthromyces corneri T.J. Baroni, T.W. Kuyper & van de Peppel 2022, in van de Peppel, Mycological Progress, 21(10), 85. (2022)

              Etymology: In honour of Edred John Henry Corner for his great contributions to the field of mycology.

              Diagnosis: Distinguished by densely caespitose collybioid basidiomata with long connate pseudorhizae, densely crowded, narrow and frequently forked lamellae, and concentrically white and grey zonate pileus with darker zones producing profuse dry arthroconidia, and by the distinct molecular profile of combined ITS, LSU, and EF1α sequences. Pileus 1025 mm wide, applanate to concave or slightly infundibuliform, disc depressed or subumbilicate, margin undulate, smooth, surface strongly velutinous but densely pruinose when older and staining fingers when handled with olive grey dusty conidia, concentrically zoned in white, dark and light grey, the darker zones covered with chains of arthroconidia. Context dull white or pale grey, soft. Lamellae densely crowded, narrow (less than 1 mm), often forked near attachment but also in the middle or near the pileus edge, pale grey or grey, edges white and fimbriate, finely eroded. Stipe 513 × 13 mm, cylindrical or compressed and twisted, gradually tapering to a long pseudorhiza, pale to dark grey, pale greyish over the pseudorhiza, surface strongly pruinose on above ground parts. Basidiospores 56 (–7) × (3–) 44.5 μm, elliptical in profile and face views, round in polar view, smooth, hyaline, wall slightly congophilous. Basidia (12–) 1520 × 56 μm, clavate or narrowly clavate, (1–) 2 and 4-sterigmate basidia present, sterigmata short, conical, 12 μm, often inconspicuous. Cheilocystidia 1840 × 2.55.5 μm, cylindrical-contorted, often branched and knobby, also some subclavate, irregularly septate, producing a thick layer of interwoven, often collapsed end cells. Pleurocystidia absent. Lamella trama composed of olive brown inflated hyphae, similar in shapes and size to those of the pileus context. Pileus context pale olivaceous brown, radially arranged, mostly inflated hyphae, (6–) 1024 μm in diam, also with scattered narrowly cylindrical, dark brown, encrusted hyphae mixed in. Pileipellis a pale or dark brown layer of repent cylindrical hyphae producing a cutis of hyphal cells, 2.55.5 μm in diam, with brown parietal pigments and distinctly darker coloured septa; producing erect end cells with straight or often curved hyaline hyphae that eventually form septa and chains of thick-walled, brown, ornamented arthroconidia, up to 10 cells in length but frequently 57 cells remain connected, individual conidia ranging from subglobose to broadly ellipsoid, 79 × 5.57 μm, some conidia becoming elongate ellipsoid or phaseoliform and these up to 1013 μm in length, thick-walled, dark yellowish brown, with obvious verrucose ornamentation. Clamp connections absent in all tissues.

              Index Fungorum Number: IF843085


Fig. 1 A Phylogenetic tree of the Lyophyllaceae, based on 1131 core nuclear genes. The termitomycetoid is highlighted in grey. B Subsection of the tree showing the phylogenetic placement of the five unidentified species of Tephrocybe in the termitomycetoid clade (Both A and B are adapted from van de Peppel et al. 2021). Support values at the nodes indicate bootstrap replicates. C Maximum-likelihood tree, based on EF1α, ITS, and LSU sequences, showing the novel species Arthromyces glabriceps nests with other species of Arthromyces. Support values at the nodes indicate ultrafast-bootstrap replicates.


Figure 2. Praearthromyces corneri D. Stubbe 06 151 Holotype. A Basidiomata in situ showing dense dark powdery arthroconidia on pileus surface. B Basidiomata showing caespitose habit. C Arthroconidia showing ornamentations. D Chain of arthroconidia from pileus surface. E Cheilocystidia. Scale bars, A and B 10 mm, CE 10 μm.



van de Peppel, L. J., Aime, M. C., Læssøe, T., Pedersen, O. S., Coimbra, V. R., Kuyper, T. W., ... & Baroni, T. J. (2022). Four new genera and six new species of lyophylloid agarics (Agaricales, Basidiomycota) from three different continents. Mycological Progress, 21(10), 85.



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