Steirochaetomium canariensis Sastoque, Stchigel & Cano 2025, sp. nov.

Steirochaetomium canariensis Sastoque, Stchigel & Cano sp. nov. MycoBank MB 849840. Fig. 12. Etymology: canariensis, from Canary Islands (Spain), due to the geographic origin of the fungus. Typus: Spain, Canary Islands, La Palma, Fuencaliente (Los Canarios), isolated from soil of Teneguía volcano, 15 Jul. 2008, coll. M. Calduch & A.M. Stchigel, isol. A.P. Sastoque (holotype CBS H-25347, culture ex-type FMR 19096 = CBS 150903). On oatmeal agar after 3 mo at 25 °C: Mycelium mostly aerial, abundant, composed of septate, branching, smooth-and thin-walled, hyaline to brown hyphae, 1–2 μm wide. Chlamydospores, hyaline, smooth- and slightly thick-walled, globose, subglobose or barrel-shaped, 11–19 × 7–13 μm, in chains, with several big lipid vacuoles (Fig. 12E, F). Sexual morph not observed. Culture characteristics (after 7 d at 25 ° C): Colony on PCA 28–29 mm diam., flat and circular; margin filamentous and regular; surface uncoloured with white (4A1) floccose aerial hyphae, sparse on the margins; soluble pigment absent; reverse uncoloured to white (4A1). Colonies on OA 25–27 mm diam., flat, circular, and expansive; margin filamentous and regular; surface greyish yellow (4B3) coloured with white (4A1) sparse aerial mycelium around and at the centre; soluble pigment absent; reverse uncoloured to greyish yellow (4B3). Colonies on CMA 31–32 mm diam., flat and circular; margin filamentous and regular; surface uncoloured with floccose white (4A1) aerial hyphae around at the centre; soluble pigment absent; reverse yellowish white (4A2). Colonies on MEA 40–41 mm diam., flat and circular; margin filamentous and regular; surface greyish yellow (4B3), with white (4A1) floccose aerial mycelium, sparse on the margins; soluble pigment absent; reverse greyish yellow (4B3). Culture iconography after 5 wk of incubation on PCA, OA, CMA and MEA (Fig. 12A–D, respectively). Minimum, optimum and maximum temperature of growth on PDA after 7 d: 15 °C, 30–37 °C and 45 °C, respectively. Additional specimens examined. Spain, Canary Islands, La Palma, Fuencaliente (Los Canarios), from soil of Teneguía volcano, 15 Jul. 2008, coll. M. Calduch & A.M. Stchigel, isol. A.P. Sastoque (culture FMR 18932). Notes: Steirochaetomium canariensis was located as a monospecific fully supported linage related but different to the Chaetomium clade (Fig. 1). Steirochaetomium canariensis does not produce fertile structures. However, it forms big chlamydospores with several big lipid vacuoles, which have not been observed in Arxotrichum, Corynascus, Chaetomium and Parachaetomium. Moreover, it is easily molecularly distinguishable from the other genera of the family Chaetomiaceae (Wang et al. 2016a, 2019a, b, 2022). Based on a BLAST search of the NCBI’s GenBank nucleotide database, the closest match using the rpb 2 sequence was Parachaetomium mareoticum [CBS 781.71, GenBank MZ342993; Identities = 598/688 (86.92 %), four gaps (0 %)]. Lastly, using the tub 2 sequence, the closest match was Parachaetomium biporatum [CBS 244.86, GenBank MK919417; identities = 427/521 (81.96 %), 23 gaps (4 %)].