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
The following material is based on the photographs and
field notes of Ron Pastorino, DNA sequencing is from
the labs of Drs. Karen Hughes and Linas Kudzma, and
other original research by R. E. Tulloss.
28 - 90 mm wide, white, with some brown stains (from
soil?), convex; context ??; margin nonstriate,
not appendiculate, apparently with short sterile
extension; universal veil as dense small
warts, granules, and pulverulence (toward margin),
white, brownish on wart tips.
adnate, close, white in mass and in side view,
attenuate, of diverse lengths, unevenly distributed,
45 - 85 × 10 - 21 mm, white, scaly-subfibrillose below partial veil, deeply inserted in substrate; bulb napiform to clavate, with brown stains; context solid; partial veil superior, membranous, proportionately large, persistent, striate above, with ochraceous staining irregular ring of universal veil on underside at edge; universal veil ??, white at first, liable to ochraceous staining.
Odor not distinctive. Taste not recorded.
bilateral, divergent; t.b.d.
35 - 47 × 9.0 - 11.3 μm, dominantly 4-, infrequently 2-sterigmate; with sterigmata ??; clamps not observed.
[40/2/1] (7.5-) 8.0 - 10.5 (-13.7) × 5.0 - 7.0 (-7.5) μm, (L = 9.2 μm; L' = 9.2 μm; W = 5.7 - 5.8 μm; W' = 5.7 μm; Q = (1.38-) 1.40 - 1.83 (-2.14); Q = 1.61 - 1.64; Q' = 1.62), hyaline, colorless, smooth, thin-walled, amyloid, ellipsoid to elongate, rarely cylindric, adaxially flattened, sometimes swollen at one end, with giant spores present early in sporulation; apiculus sublateral, cylindric; contents granular or monoguttulate with or without additional small granules; white in deposit.
In groups. At ca. 190 m elev. In dry soil
with Pseudotsuga mendiesii and
Umbellularia californica or in
Quercus agrifolia woodland.
Alameda Co. - Berkeley, Univ. of Calif. [37.8803° N/
122.2465° W, 347 m], 6.xii.2009 unkn. coll. s.n.
(RET 689-5, nrITS seq'd.).
Marin Co. - Alpine Lake [37.948º N/ 122.628º W,
198 m], 25.xi.2016 Ron Pastorino s.n. [mushroomobserver
(RET 745-4, nrITS seq'd.); Lake Lagunitas, 27.ii.2016
Ron Pastorino 2-27-16A) [mushroomobserver
(RET 860-1, nrITS-LSU seq'd.).
Mendocino Co. - Albion, 25-28.xi.2004
unkn. coll. s.n. (RET 382-3, nrITS-LSU seq'd.).
Orange Co. - Upper San Juan Campground
[33.5347° N/ 117.5530° W, 117 m],
27.iii.1982 Richard Therrien & Kris McAdam s.n.
[Greg Wright 2563] (RET 081-4, nrITS seq'd.).
San Diego Co. - Tecolote Canyon Nat. Pk., 9.i.2019
Cindy Trubovitz s.n. [iNaturalist
(RET 863-4, nrITS-LSU seq'd.).
San Mateo Co. - Woodside [37.4241° N/ 122.268° W, 137 m],
12.xii.2013 Bill Yule s.n. [mushroomobserver.org
(RET 690-1, nrITS seq'd.).
Santa Cruz Co. - Cabrillo College campus, 20.xii.2015
Leonard Treio s.n. [mushroomobserver
(RET 722-7, nrITS seq'd.).
Sonoma Co. - Santa Rosa, Annadel St. Pk. [38.4026°
N/ 122.5804° W, 188 m], 27.xi.2007 R. Pastorino
11-27-07A [mushroomobserver.org #5264]
(RET 585-7, nrITS seq'd.).
This species lacks the distinctive subsurface
A. novinupta although it may
blush in age. It has a more distinctive bulb,
narrower spores. The following sporograph
comparison illustrates the last point:
Although their bruising is different and they can be
distinguished genetically, the spores of the
present species are very similar to those of
The material examined to date has been somewhat
immature, which may account for the presence of
giant spores and 2-sterigmate basidia.
This species has been mistaken for
"Amanita cokeri sensu Thiers" in the
field. The taxa can be differentiated
easily by the great thickness of the universal
veil in the latter entity and its lack of a
well-developed pileipellis. RET considers
it probable that Thiers' concept of cokeri
is based on immature material of A. magniverrucata of
The name Amanita sponsus replaces the
temporary code Amanita sp-C20, which was
previously treated in these pages.
This species was designated Amanita “sp. C4” by
RET in the 1980s. The temporary code was
based on a single collection (RET 081-4) that was
a gift from the herbarium of Greg Wright, who had
recognized the material as representing a new
species. Also, this species was briefly called
"A. sp-C30" on the present site.
—R. E. Tulloss and R. Pastorino
Information to support the viewer in reading the content of "technical" tabs
can be found here.
Tulloss et al.
1. Amanita sponsus, Annadel St. Pk., Santa Rosa, Sonoma Co., California, U.S.A. (RET 585-7)
2. Amanita sponsus, Annadel St. Pk., Santa Rosa, Sonoma Co., California, U.S.A. (RET 585-7)
3. Amanita sponsus, Annadel St. Pk., Santa Rosa, Sonoma Co., California, U.S.A. (RET 585-7)
4. Amanita sponsus, Annadel St. Pk., Santa Rosa, Sonoma Co., California, U.S.A. (RET 585-7)
5. Amanita sponsus, Tecolote Canyon Nat. Pk., San Diego Co., California, U.S.A. (RET 863-4)
6. Amanita sponsus, Tecolote Canyon Nat. Pk., San Diego Co., California, U.S.A. (RET 863-4)
7. Amanita sponsus, Tecolote Canyon Nat. Pk., San Diego Co., California, U.S.A. (RET 863-4)
Ronald Pastorino - (1-4) Annadel St. Pk., Santa Rosa,
Sonoma County, California, U.S.A.
(RET 585-7) [Note: These images can be viewed in
their original size and format on
Cindy Trubovitz - (5-7) Tecolote Canyon Natural Park, San
Diego County, California, U.S.A. (RET
863-4). [Note: Original unedited and
uncut images can be found
Spore data for collections provisionally identified as: Amanita sponsus Tulloss et al.
Each spore data set is intended to comprise a set of measurements from a single specimen made by a single observer;
and explanations prepared for this site talk about specimen-observer pairs associated with each data set.
Combining more data into a single data set is non-optimal because it obscures observer differences
(which may be valuable for instructional purposes, for example) and may obscure instances in which
a single collection inadvertently contains a mixture of taxa.