Tetrapyrgos atrocyanea ( Métrod 1949: 140 ) E. Horak (1986: 102)

Reschke, Kai, Lotz-Winter, Hermine, Fischer, Christian W., Hofmann, Tina A. & Piepenbring, Meike, 2021, New and interesting species of Agaricomycetes from Panama, Phytotaxa 529 (1), pp. 1-26 : 19-20

Tetrapyrgos atrocyanea ( Métrod 1949: 140) E. Horak (1986: 102) , Fig. 13h

Description:—Basidiocarps marasmioid. Pileus 0.8–1.2 cm diam., convex to plane, umbilicate, with rather straight margin, greyish yellow to olive yellow (2C3–5, 2D5–6) at central disk, paler, white with greyish-yellowish tinge towards the margin, surface covered by fine powdery, white flocks, sulcate-striate up to the centre. Lamellae broadly adnate to decurrent, medium spaced to rather distant, whitish, with somewhat uneven, concolorous edges, and intervenose ridges. Stipe 1.0–1.3 × 0.1 cm, cylindrical, straight, white, pale grey (21B1) to light grey (21C1) in immature basidiocarps, later dark grey, blackish (21F1 and darker) to bluish grey (21F2), paler bluish grey, medium grey to light grey (21D1– 2, 21E1–2) towards the tip, covered by white, powdery flocks. Base of the stipe often emerging from a dark, bluish grey mycelial disk. Odour indistinct, taste not tested.

Basidiospores 7.5–9.0–10.5 × 5.5–6.7–8.0 µm, Q = 1.10–1.35–1.70 (n = 30 spores of 1 specimen), tetrahedral, hyaline, thin-walled. Basidia 4-spored, clavate, hyaline, immature basidia often fusiform. Lamellar edge sterile. Cheilocystidia 30–42(–54) × 3.0–5.0 µm, diverticulate, sometimes septate, with knob-like apex. Pileipellis a ramealesstructure with strongly diverticulate end cells. Clamp connections abundant in all parts of the basidiocarp.

Habitat: —Basidiocarps solitary or in small, dense groups on woody litter, found on woody roots on a path in secondary vegetation in lowlands of Chiriquí Province, Panama.

Notes: — Tetrapyrgos atrocyanea is the type species of the genus Tetrapyrgos Horak. It was described from Madagascar by Métrod (1949) and an epitype was recently designated by Desjardin et al. (2017), together with a detailed description and molecular sequences. Tetrapyrgos atrocyanea has a wide distribution, in addition to Madagascar it is known from Benin ( Piepenbring et al. 2020), Bolivia, Brazil ( Komura et al. 2020), Costa Rica, and Puerto Rico ( Desjardin et al. 2017; Honan et al. 2015). Often, Tetrapyrgos specimens in the tropics and subtropics were referred to as Tetrapyrgos nigripes ( Fries 1838: 383) E. Horak ( Horak 1983; Piepenbring et al. 2018; Redhead 1989; Singer 1973). This species was described from North Carolina, USA, and has a white pileus, and in average shorter cheilocystidia than T. atrocyanea ( Honan et al. 2015) . ITS sequences corresponding to authentic specimens of T. nigripes from North Carolina and Tennessee, USA, have no matches with tropical or subtropical material ( Honan et al. 2015; Komura et al. 2020). Also, further, unpublished sequences of Tetrapyrgos specimens from Benin and Panama do not match those of authentic T. nigripes specimens.

Specimens examined: — PANAMA. Chiriquí Province: Los Algarrobos, trail to Río Majagua , 120 m a.s.l., border of the trail, 1 June 2017, K. Reschke KaiR331 (M-0312090) !; ibid., 5 June 2017, K. Reschke KaiR395 (M-0312091) !.