Agaricus caballeroi

Agaricus caballeroi L.A. Parra, G. Muñoz & Callac, Micol. Veg. Medit. 29(1): 22. 2014

MycoBank MB808465

Taxonomic clasification

phy Basidiomycota

sbp Agaricomycotina

cls Agaricomycetes

sbc Agaricomycetidae

ord Agaricales

fam Agaricaceae

gen Agaricus

sp Agaricus caballeroi


Pileus 4-10 cm in diameter, at first globose, then convex and finally applanate; surface dry, dull, at first smooth, later remaining either smooth or breaking up into appressed scales, which are usually hardly conspicuous because diffusely overlapping, even in fully expanded specimens, reddish-brown, dirty brown or ochraceous-brown on a paler or whitish background, showing a tendency to develop copper-coloured or ferruginous-brown stains with time or on handling. Margin long inflexed, connected to the stipe by the universal veil in immature specimens, then after the pileus expansion the margin remains attached to the stipe by a wide thick partial veil, finally lacking appendiculate remnants, regular, not or only shortly (1 mm) exceeding the lamellae when it separates from the partial veil. Lamellae free, up to 1 cm broad, crowded, intercalated with lamellulae. At first whitish, soon very pale pink, then bright pink, after greyish-brown, finally dark brown almost black. Edge finely serrate and lighter-coloured in young basidiomes, but soon concolorous with the faces; when young staining dark pink on touching. Stipe 2.5-10 x 1.5-4 cm, cylindrical, ventricose or clavate, frequently abruptly tapered into a pointed base, stocky, fistulose in fully ripe specimens, with an annulus in the upper half, white and smooth above the annulus, below smooth and white, but often towards the base with dark orangish volvate remnants of the universal veil, either appressed or slightly detached from the stipe in its upper limb, even though at times, especially in dry weather, the veil remnants may disappear rapidly, then showing a pale whitish colour as the rest of the stipe. The stipe base is subtended by few, obvious, very long and thick rhizomorphs, which in some specimens may be up to 6-7 cm long. In some basidiomes can also be observed thin mycelial strands. Annulus superous, thin at the attachment on the stipe, thicker and often double towards the margin, up to 1.6 cm broad, membranous, pendent, usually double, obviously striate on the upper side, fibrillose and often decorated with scales concolorous with the pileus on the antemarginal zone of the underside, the scales may occasionally be arranged into a cogwheel; sometimes the annulus is simple due to the absence of scales on underside. Characteristically, in immature specimens cut lengthwise, it can be observed a woolly partial veil (from which the annulus originates), which is very thick where it joins the unrolled pileus margin, and is externally overlaid with the very thin universal veil. Such a partial veil, with the growth of the basidiome, becomes thinner and separates from the universal veil giving rise to a triangular chamber (in section) between the two veils, which then disappears when the universal veil breaks up. Context white on cutting, changing slowly to a pale pinkish or reddish, both in the pileus and stipe. Odour agreeable, not distinctive, neither of anis or bitter almonds nor of ink or phenol. Spores 4.8-5.7-6.5(-6.9) x 3.9-4.5-5.2(-5.4) μm, Q= (1.07-)1.1-1.28-1.5, subglobose to ellipsoid, of a light brown colour, smooth, thick-walled, lacking an apical pore, generally monoguttulate. Basidia 25-35 x 6.5-10 μm, generally tetrasporic, but often intermixed with bi- or monosporic basidia above all near the lamellar edge – in some mounts it was observed that the number of bisporic basidia was similar to that of the tetrasporic ones – clavate or slightly truncate at the apex, hyaline, with sterigmata up to 7 μm. Cheilocystidia present, inconspicuous and difficult to separate from basidioles, simple or with various septa towards the base, cylindrical with enlarged apex, clavate or ovoid, hyaline. The simple cheilocystidia and the terminal elements of the septate ones measure 15.5-30 x 4-13 μm, the anteterminal elements measuring 6-12 x 4-7 μm. Pleurocystidia none. Lower surface of the annulus consisting of cylindrical hyphae 2-11 μm wide, not or slightly constricted at septa; the observed terminal elements cylindrical or enlarged at the apex, which is rounded and 4-6 μm wide. Pileipellis a cutis of hyphae 2-12 μm wide, not or slightly constricted at septa; the terminal elements observed were very similar to those in the lower surface of the annulus and 4-6 μm wide. Clamp connections absent in all structures studied.

Macrochemical reactions: Schäffer and KOH reactions negative everywhere. Alpha naphthol negative on the context, positive, purple, just below the pileipellis, on the annulus and around the maggot holes.

Habit, phenology, habitat and distribution: Generally fruiting in groups, often numerous, sometimes also solitary. Autumn. So far collected only in Spain, in two localities of the province of Zaragoza.


References in our territory
  • Parra LA, Muñoz G, Callac P. 2014. Agaricus caballeroi sp. nov., una nueva especie de la sección Nigrobrunnescentes recolectada en España. Micol. Veget. Medit. 29(1): 21-38.


Specímenes in scientific collections

* sequenced material

Reference specimen marked in bold

GM: G. Muñoz private herbarium

LAPAG: L. A. Parra private herbarium

Z: Zaragoza: GM-1545 (duplicate LAPAG 865); GM-1546 (duplicate LAPAG 866); GM-1569 (duplicate LAPAG 867); GM-1937* (duplicate LAPAG 775); GM-1990 (duplicate LAPAG 868); LAPAG 799; GM-2232; GM-2233; GM-2234 (duplicate LAPAG 806); GM-2248; GM-2272; GM-2273; GM-2312; GM-2332; GM-2364; GM-2564; GM-2573; GM-2418; GM-2644; AH-44503*, holotype (isotype: GM-2541 y LAPAG 795); GM-2440; Gallur: GM2691*.


Sequences in public databases obtained from material collected in our territory

AH-44503: KJ575605 (ITS)

GM-2691: KJ575606 (ITS)

GM-1937: KJ575607 (ITS)



Photo: L.A. Parra, specimen AH44503 (Holotype)