The cap of A. yucatanensis is 25± mm wide,
convex to near planar, smooth, dry, and has a striate
margin. It is white to pale yellowish. The flesh is
white. The volva is absent or is present as scattered
irregularly shaped, whitish, thin, flat patches.
The gills are narrowly
adnate, white to whitish rose, drying pale orange-brown,
with fimbriate edges. The short gills are truncate and
The stem is 12± (?) × 5± mm, narrowing markedly upward,
floccose-scaly below, pruinose above, and exannulate. The
volva is a white, delicate, membranous sac.
The spores measure (7.8-) 9.5 - 13.0 (-14.2) × (7.0-) 7.5 - 9.5
(-11.8) µm and are inamyloid and broadly ellipsoid to ellipsoid
(occasionally subglobose). Clamps are sometimes present at bases of
basidia; they are occasionally rather small and somewhat
difficult to locate in some sections.
Amanita yucatanensis was
originally described from the state of Yucatán, Mexico
in "secondary, perennial tropical rain forest."
It is still known only from the original collections cited by Guzmán.
According to current understanding
of systematics of Amanita section Vaginatae,
A. yucatanensis seems to be a rather isolated
neotropical taxon. Perhaps, the closest relationship is
with the Mediterranean group of taxa related to A. mairei Foley.—R. E. Tulloss
The following text may make multiple use of each data field.
The field may contain magenta text representing a type study
or a study of original material by Tulloss.
The same field may also contain black text, which will represent a revision of the
species by Tulloss. Paragraphs of black text will be labeled if further subdivision of
this text is appropriate.
Olive text indicates a specimen that has not been
thoroughly examined (for example, for microscopic details) and marks other places in the text
where data is missing or uncertain.
Macroscopic data is from the protolog of the present species and Tulloss' examination of the isotype. Microscopic data is from (Tulloss 1994).
Tulloss (1994): 25± mm wide, convex to near planar, smooth, dry, white to pale yellowish; context white; margin striate; universal veil absent or as scattered irregularly shaped, whitish, thin, flat patches; pileipellis easily peeling in exsiccatum.
Tulloss (1994): narrowly adnate, white to whitish rose, drying pale orange-brown (more yellow than 7.5YR 7/6 and close to 5B5), with fimbriate edges (remaining pale in exsiccatum); lamellulae truncate, unevenly distributed.
Tulloss (1994): 12±(?) × 5± mm, narrowing markedly upward, floccose-scaly below, pruinose above; context not recorded; exannulate; universal veil as membranous saccate volva, white, delicate.
Tulloss (1994): 20 - 40 µm thick, extensively gelatinizing at the surface; filamentous, undifferentiated hyphae 1.5 - 4.5 µm wide, subradially oriented, interwoven, densely packed, more yellow brown than adjacent context; refractive hyphae 2.5 - 7.0 µm wide, branching, locally common, sometimes descending into pileus context.
Tulloss (1994): filamentous, undifferentiated hyphae 2.2 - 12.5 µm wide, loosely interwoven, branching, often constricted at septa, with some terminal segments narrowly clavate; acrophysalides thin-walled, broadly clavate to ovoid to ellipsoid to oblong to subcylindric, up to 98 × 36 µm; refractive hyphae 2.8 - 7.8 µm wide, branching, common.
Tulloss (1994): bilateral, in some sections obscurely so; wcs = 50* µm; in some sections dominated by a densely tangled central stratum, imperfectly rehydrating; filamentous, undifferentiated hyphae 2.0 - 7.5 µm wide, subparallel to hymenial surface, sometimes obscuring both inflated intercalary cells and divergent elements, with inflated intercalary segments ellipsoid to subcylindric, up to 42 × 23 µm; apparently terminal, inflated cells resulting from sectioning, with major axis parallel to hymenial surfaces or diverging (as result of sectioning and mounting) at angles up to 45°; vascular hyphae not observed.
Tulloss (1994): wst-near = 5± µm; wst-far = 35± µm; branching structure dominated by filamentous, undifferentiated hyphae, although with small inflated cells rather plentiful in some regions; basidia arising from small ovoid to subglobose cells and from uninflated or slightly inflated hyphal segments; filamentous, undifferentiated hyphae present running subparallel to hymenial surface near bases of longer basidia. [Note: This description suggests that the material was imperfectly rehydrating.]
Tulloss (1994): 54 - 70 × 9.0 - 17.0 µm, thin-walled, 4-, or occasionally 2-sterigmate; clamps present, occasionally rather small and somewhat difficult to locate in some sections.
Tulloss (1994): On pileus: absent. At stipe base, exterior surface: surface layer with thickness of only one or two hyphal diameters; filamentous, undifferentiated hyphae 1.0 - 6.0 µm wide, dominating, loosely woven, often in fascicles, many sublongitudinally oriented, partially gelatinized; inflated cells uncommon, nearly fully gelatinized, having same form as those of interior; refractive hyphae 2.8 - 6.5 µm wide, lacking a common orientation, sometimes included in fascicles. At stipe base, interior: filamentous, undifferentiated hyphae 1.5 - 10.2 µm wide, dominating, sometimes with very narrowly fusiform intercalary segments, branching, loosely interwoven, constricted at septa, commonly with irregular, flat plaques less than 0.5 µm thick on surface; inflated cells clavate to narrowly clavate to ventricose, terminal, thin-walled or with walls slightly thickened, at times with exterior wall having small surface plaques as in hyphae (only seen on thin-walled cells or on thin-walled parts of cell surfaces), up to 79 × 39 µm; vascular hyphae not observed. At stipe base, inner surface: filamentous, undifferentiated hyphae in fascicles, partially gelatinized, fragmented, occasional; inflated cells slightly narrower on average than in interior; otherwise, like interior.
Tulloss (1994): longitudinally acrophysalidic; filamentous, undifferentiated hyphae 1.4 - 10.5 µm wide, plentiful, branching; acrophysalides up to 186 × 39 µm, thin-walled; refractive hyphae 0.7 - 8.8 µm wide, especially frequent near stipe surface; clamps observed.
Tulloss (1994): [40/1/1] (7.8-) 9.5 - 13.0 (-14.2) × (7.0-) 7.5 - 9.5 (-11.8) µm, (L = 11.6 µm; W = 8.7 µm; Q = (1.11-) 1.17 - 1.44 (-1.53); Q = 1.33), hyaline, colorless, smooth, thin-walled, inamyloid, broadly ellipsoid to ellipsoid, occasionally subglobose, dominantly adaxially flattened, sometimes expanded in middle, often expanded at one end; apiculus sublateral, infrequently lateral, cylindric; context dominantly monoguttulate with a few small granules; color in deposit not recorded.
Tulloss (1994): Solitary on soil. In secondary, perennial, tropical rain forest.
Tulloss (1994): MÉXICO: QUINTANA ROO—Road to Vallarta, ca. crossing from Puerto Morelos to Tulum Road, 10.xi.1981 G. Guzmán 21044 (holotype, ENCB n.v.; isotype, XAL).
Tulloss (1994): The length of the stipe given in the protolog must be in error. The isotype specimen I examined has a very thin stipe exceeding the length reported for the fresh material.
The exterior decoration of cell walls in the universal veil is limited to cases in which the walls otherwise are not thickened. This suggests that the cells have one or more outer layers that rupture in a roughly areolate manner thus giving rise to the patches observed—superimposed on a thin, innermost, tegumentary layer.
As in the case of A. dunicola, a comparison to A. argentea, A. huijsmanii, and A. supravolvata is warranted. The pilei of these taxa are shades of gray or brown. Their universal veil, when it is left on the pileus, takes the form of a rather thick, white patch over the disc. The margins of their pilei are markedly striate. The pileipellis in A. argentea and A. huijsmanii is thicker than in A. yucatanensis and exhibits a criss-cross pattern of somewhat refractive elements. Surface plaques are lacking on all elements of the anatomy of the European taxa. Amanita supravolvata lacks divergent, terminal, inflated cells in the lamella trama and lacks hyphae of the trama running parallel to the central stratum close to the bases of longer basidia.
Comparison to A. dunicola is provided in the discussion following the description of that species.
—R. E. Tulloss
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