THE VELIGER
CMS, Inc., 2000
The Veliger 43(4):367-375 (October 2, 2000)

A New Species of Hydrobiid Snail of the Genus Pyrgulopsis from
Northwestern Nevada
ROBERT HERSHLER
Department of Invertebrate Zoology,
National Museum of Natural History, Smithsonian Institution, Washington, DC. 20560-0118, USA
AND

DONALD W. SADA
Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512 and Biological Resources Center,
University of Nevada, Reno, Nevada 89557, USA
Abstract. Pyrgulopsis bruesi new species, from northwest Nevada, differs from closely similar P. augustae on thebasis of its higher-spired shell, larger penial filament, and more ventrally positioned seminal receptacle. This species isendemic to a thermal spring area in a small basin which was inundated by pluvial Lake Lahontan.

INTRODUCTION
Pyrgulopsis is the largest genus of freshwater mollusks
in North America, with more than 130 species currently
placed in this group (Hershler, 1994, 1995; Thompson,
1995; Hershler, 1998). Whereas these small, gill-breathing snails are broadly distributed in southern North America, the greatest diversity of Pyrgulopsis is in the GreatBasin, a vast expanse of internal drainage lying between
the Wasatch Front and Sierra Nevada of the western United States. Within this region most congeners are restricted
to seeps and spring sources, while only a few species livein more integrated stream habitats. The isolated nature ofthese water bodies, reinforced by surrounding arid environments, has been highly conducive to differentiation ofthese poorly dispersing snails. Eighty species of Pyrgulopsis are now known from the Great Basin (Hershler &Sada, in press).
We recently collected biota at Fly Ranch Hot Springs(also known as Ward's Hot Springs; Garside & Schilling,1979), north of Gerlach, Nevada. The small invertebrate
assemblage of mollusks and crustaceans inhabiting thermal waters at this locality, which is part of a well-definednortheast-trending zone of thermal springs in northwest
Nevada (Hose & Taylor, 1974:fig. 2), included a new species of Pyrgulopsis, which is described below. This new
species is most similar morphologically to several congeners also living in the Great Basin of Nevada.
MATERIALS AND METHODSSpecimens are deposited in the National Museum of Natural History, Smithsonian Institution (USNM). Terminology and methods of morphological analysis are of Her-

shler (1998) and Hershler & Ponder (1998). Measurements of shells of the holotype and a series of paratypes
are in Table 1.
SYSTEMATICS
Pyrgulopsis bruesi Hershler & Sada, sp. nov.
Type material: The holotype (USNM 892079) is a driedshell (2.55 mm shell length, Figure 1) from a small
stream which enters Fly Reservoir, about 23 airline-km
north-northeast of Gerlach, Washoe County, Nevada, T
34 N., R. 23 E., SE % section 2, elevation about 1238 m;
collected by R. Hershler and D. W Sada, 19 July 1997.
Paratypes (USNM 860868) consist of a large series ofdry shells and alcohol-preserved specimens collectedfrom the type locality at the same time. Two additional
series (USNM 892075, 892584), which are not designatedas paratypes, were collected at the type locality by D. W.
Sada at other times in 1997.
Diagnosis: A medium-sized species with ovate-conic
shell having weakly rounded whorls. Penis small, narrowbladelike; filament medium length, lobe and penial glands
absent.
Description: Shell (Figure 2A-C) ovate-conic, almost
pupiform, width/height, 49-58%; height, 2.02-3.03 mm;
width, 1.13-1.74 mm; whorls, 4.5-5.25. Protoconch near
planispiral, 1.4 whorls, diameter about 300 u,m, earliest
0.5 whorl slightly wrinkled, otherwise smooth (Figure2D-F). Teleoconch whorls weakly convex or nearly flat
(earlier whorls somewhat more rounded), sometimes narrowly shouldered, basal portion sometimes strongly an-

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Table 1Morphometric and meristic shell features of holotype andranges of values for 10 paratypes of Pyrgulopsis bruesi,
new species. Morphometric parameters are expressed inmm.

Shell height
Shell width
Body whorl height
Body whorl width
Aperture height
Aperture width
Shell width/shell height
Number of whorls

Holotype

Paratypes

2.55
1.47
1.82
1.27
0.99
0.87
0.57
4.75

2.38-2.75
1.19-1.47
1.56-1.90
1.15-1.41
0.85-1.07
0.82-0.93
0.49-0.58
4.75-5.25

gled; sometimes loosened for 0.25 whorl behind aperture.
Aperture ovate, broadly adnate or slightly disjunct. Inner
lip complete, slightly thickened; columellar lip sometimes
slightly reflected. Outer lip thin, orthocline or weakly prosocline, sometimes weakly sinuate. Umbilicus narrow.
Periostracum tan. Shells of males narrower, with flatterwhorls, and slightly smaller than those of females.
Operculum (Figure 2G-I) thin, light amber throughout
or colored only in attachment region, ovate, multispiral,
nucleus eccentric. Edges of whorls frilled on outer surface (Figure 2G, H), sometimes markedly so; outer margin sometimes having weak rim. Attachment scar margin
strongly thickened between nucleus and inner edge (Figure 21), sometimes thickened all around.
Buccal mass medium-sized; radular sac extending behind buccal mass as small loop. Radula about 530 X 80
u,m, with 55-60 rows of teeth. Central teeth (Figure 3A,B) trapezoidal, about 18.6 u,m wide, dorsal edge well indented; lateral cusps 4-6; central cusp medium width,
proximal edges parallel, distal portion pointed; basal cusp
1, large. Basal tongue broad V-shaped, basal sockets
deep. Lateral teeth (Figure 3C) with 2-3 cusps on innerside and 3-5 cusps on outer side, central cusp rather
broad; neck weakly flexed; outer wing length 200% widthof tooth face. Inner marginal teeth (Figure 3D) with 2127 cusps, outer marginal teeth (Figure 3E, F) with 23-27
cusps. Style sac about as long as remainder of stomach;stomach with small posterior caecum.
Cephalic tentacles usually unpigmented, sometimes
pigmented with a few black granules proximally. Snout

Figure 1
Holotype of Pyrgulopsis bruesi Hershler & Sada, sp. nov., fromFly Hot Springs, Washoe County, Nevada.

unpigmented. Foot usually unpigmented, sometimes pigmented with scattered black granules dorsally. Opercularlobe black along inner edge. Neck variably pigmented
with black granules. Pallial roof, visceral coil lightly pigmented to near black, pigment lighter on genital duct thanelsewhere. Males usually with darker pigment on mantle
roof and visceral coil than females. Filament of penis almost uniformly pigmented with internal black granules,
granules scattered proximally along length of penial duct.
Dorsal and ventral surfaces of tentacles bearing single
longitudinal ciliary tracts. Distal penis bearing scatteredlong cilia near terminus, otherwise unciliated.
Ctenidium well developed; filaments 18-20, withpleats, broadly triangular, apices centrally positioned; ctenidium abutting pericardium posteriorly. Osphradium
rather long, intermediate width, near centrally positioned.
Renal gland longitudinal; kidney with small pallial bulge,
opening slightly thickened. Rectum near straight, broadly
overlapping pallial oviduct, abutting prostate gland.
Ovary 0.75 whorl, filling less than 50% of digestive
gland behind stomach, abutting posterior edge of stomach. Albumen gland (Ag) having substantial pallial corn--»
Figure 2
Scanning electron micrographs of shell and opercula of P. bruesi Hershler & Sada, sp. nov. USNM 860868. A-C.
Variation in shell shape (shell height, 2.58 mm, 2.43 mm, 2.68 mm, respectively). D-F. Shell apices, showing weak
protoconch sculpture (bars = 120 u.m). G, H. Outer surface of operculum (bars = 240 |xm, 200 jjum, respectively).
I. Inner surface of operculum, showing thickened border of muscle attachment area near nucleus (bar — 240 urn).

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Figure 3
Scanning electron micrographs of radula of P. bruesi Hershler & Sada, sp. nov. USNM 860868. A, B. Central
radular teeth (bars = 9.2 u.m, 10.9 |xm, respectively). C. Lateral tooth (bar = 10.9 |xm). D. Inner marginal tooth(bar = 12.0 u,m). E, F. Outer marginal teeth (bars = 12.0 |xm).

ponent (Figure 4A). Capsule gland (Cg) slightly shorter,
about as wide as albumen gland, divided into two equalsized tissue sections (anterior, clear; posterior, white),broadly ovate in section, right lobe thicker than left; rectal
furrow absent. Ventral channel (Vc) broadly overlapping
capsule gland; longitudinal fold well developed. Genital
aperture (Ga) a long terminal slit. Coiled oviduct (Cov)of two overlapping posterior-oblique loops. Oviduct andbursal duct joining just behind pallial wall. Bursa copulatrix (Bu) small relative to albumen gland, narrow orovate, longitudinal, up to 50% of length posterior to albumen gland. Bursal duct originating from anterior edgeat midline, slightly longer than bursa copulatrix, narrowor medium width (Figure 4B). Seminal receptacle (Sr)small relative to bursa copulatrix, ovate, positioned along
ventral edge of distal oviduct coil and usually just anterior

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R. Hershler & D. W. Sada, 2000

B // C

Figure 4
Genitalia of P. bruesi Hershler & Sada, sp. nov. USNM 860868. A. Left side of female glandular oviduct andassociated structures. B. Bursa copulatrix and its duct. C. Seminal receptacle and its duct. D. Left side of prostate
gland, showing insertion of vas deferens. E. Penis. Bars = 0.25 mm. Ag = albumen gland, Bu = bursa copulatrix,
Cg = capsule gland, Cov = coiled oviduct, Ga = genital aperture, Pd = penial duct, Pvd = pallial vas deferens,
Pr = prostate gland, Pw = posterior wall of pallial cavity, Sr = seminal receptacle, Vc = ventral channel of capsulegland, Vvd = visceral vas deferens.

to bursa copulatrix, duct slightly shorter than body (Figure 4C).
Testis 1.5-2.0 whorls, composed of numerous compound lobes, filling about 50% of digestive gland behindstomach, broadly overlapping stomach anteriorly. Seminal vesicle a medium-sized mass of tight coils opening
from and positioned alongside the anterior portion of testis. Prostate gland (Pr) small, bean-shaped, pallial portion
about 33% of total length, narrowly ovate in section (Figure 4D). Visceral vas deferens (Vvd) opening to ventraledge of prostate gland just behind pallial wall. Pallial vas
deferens (Pvd) opening to ventral edge of prostate glandjust in front of posterior wall; duct having distinct proximal bend on columellar muscle. Penis small; base elongate-rectangular, smooth; filament about 33% length ofbase, gently tapering, distally pointed, rather broad, longitudinal, poorly distinguished from base (apart fromdarker pigmentation); lobe and glands absent (Figure 4E).
Penial duct (Pd) near inner edge, narrow, undulating a
few times near base, otherwise near straight.
Etymology: A patronym, named after the late Charles
Thomas Brues II (1879-1955) who, in addition to his
notable studies in entomology (Mallis, 1971), surveyed

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thermal springs of the western United States (Brues,
1928, 1932) and brought the interesting biota of thesehabitats to the attention of the biological community.
Brues (1932:206) early visited the type locality area("sixteen miles northwest of Gerlach"), although he did
not collect any snails. We propose the vernacular name,"Fly Ranch pyrg," for this species in reference to its type
locality.

Distribution: This species is thus far known only fromits type locality. During the course of our field survey,
other sites in the Hualapai Flat basin were searched anddid not yield this snail, although a congener, P. gibba,
was collected from the flanking Granite Range (Hershler,
1998).

Comparisons: Pyrgulopsis bruesi and a small group ofcongeners share a simple penis without lobe or glands.
Among these, P. bruesi is most similar to P. augustae
Hershler, 1998, which lives about 190 km to the southeast(Antelope Valley, Lander County), but differs on the basisof its higher-spired shell (compare Figure 2A-C with
Hershler, 1998:hg. 9B), larger penial filament (compare
Figure 4E with Hershler, 1998:fig. 40A), and more ventrally positioned seminal receptacle (compare Figure 4A
with Hershler, 1998:fig. 40B). These two species, together
with another congener from the Great Basin of Nevada(P. dixensis Hershler, 1998) having a simple penis, areunited by their narrow shell and distinctive thickening of
the operculum attachment region border near the nucleus.

Pyrgulopsis has occupied habitats of the northern GreatBasin since at least the late Miocene (Hershler & Sada,
in press), and several scenarios for the origin of P. bruesi
may be conjectured. Hualapai Flat is a small (about 200
km2), endorheic, north-south trending graben bounded to
the west by the imposing Granite Range. The Calico Hills
form a lower hydrographic barrier to the northeast, while
to the southeast Hualapai Flat is separated from the Black
Rock Desert by an alluvial divide of only about 30 m
(Sinclair, 1962). Thick Quaternary deposits on the floorof Hualapai Flat include fine sections attributable to Lake
Lahontan, which also left sedimentary exposures elsewhere in the basin (Grose & Sperandio, 1978). Highstandelevations of Lake Lahontan (from Mifflin & Wheat,1971) imply that the Fly Hot Springs area was flooded
by a > 100 m deep embayment during the late Pleistocene. Evolution of P. bruesi may be attributable to isolation in basinal spring habitats coincident with the final
recession of Lake Lahontan about 13,000 ybp.
Pyrgulopsis bruesi is one of many congeners that areendemic to flowing thermal waters. Experimental data indicates that while these snails actively prefer thermal habitats, they can tolerate considerably lower water temperatures (Mladenka, 1992). Invasion of Hualapai Flat from
elsewhere in the Lahontan basin via dispersal within pluvial waters may thus be tenable for progenitors of P.
bruesi. Congeners that are most similar morphologicallyto P. bruesi also live within (P. augustae) or adjacent to(P. dixensis) the Lahontan basin, supporting a hypothesisthat these were all derived from a widespread pluvial progenitor. Note that recently acquired evidence of high elevation early Pleistocene shorelines (about 1400 m) in theLahontan basin implies that Dixie Valley (which harbors
P. dixensis) may have been integrated with this regional
drainage (Reheis, 1996; Rebels & Morrison, 1997), instead of containing an isolated pluvial lake as traditionally viewed (Mifflin & Wheat, 1979).
Alternatively, one may attribute less importance to pluvial dispersal of snails and postulate an earlier (pre-Pleistocene) origin of P. bruesi coincident with regional development of the modern basin and range landscape. Topographic closure of Hualapi Flat during the Neogene
may be inferred by its location along the edge of theBlack Rock-Carson Sink zone of extension, a tectonically
active area of broad alluviated grabens whose youthfuldevelopment involved extensive deformation of 17-6 ma
extrusive igneous rocks (Wallace, 1984). On a local scale,

Habitat: The Fly Ranch Hot Springs is the largest springzone in northwest Nevada (Garside & Schilling, 1979),
consisting of about 40 sources (Grose & Keller, 1975)
that collectively discharge about 500 acre-feet/year (=0.69 cfs) (Sinclair, 1962). Thermal sources are located ona large mound and discharge into a series of pools, withdrainage ultimately entering the Fly Reservoir (Figure 5).
This hot spring area has been modified by surface water
diversion, groundwater mining, dredging, and recreational activity.
Pyrgulopsis bruesi was collected from a turbid, 1 m
deep and 1.5 m wide stream (Figure 6) fed by natural
springs and a flowing well whose effluents have givenrise to an impressive, three-pronged travertine tower (asecond, similarly active tower, slightly north of the above,
was figured by Sinclair, 1962:fig. 1; and Garside & Schilling, 1979:74). Water quality data obtained from thisstream on 20 September 1997 are as follows: water temperature, 27.0°C; conductivity, 1760 mhos/cm; pH; 8.2;
and dissolved oxygen content, 6.7. Snails were collectedfrom submerged unidentified aquatic vegetation on which
they were moderately abundant; fewer specimens were
found on Cattail (Typha). Although considerably cooled
relative to the boiling effluent of the well, this stream
nonetheless ranks as a regional thermal water body as
variously defined (e.g., Waring, 1965:4; Garside & Schilling, 1979:1). Another hydrobiid snail, Tryonia protea,
which is broadly distributed in western North America(Hershler, 1999); pulmonate gastropods, Helisoma anceps
and Physella virgata, and an unidentified amphipod werecollected in association with P. bruesi. The tui chub, Gilabicolor, also is present in this stream (Brues, 1932).

DISCUSSION

R. Hershler & D. W. Sada, 2000

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Figure 5
Location of type locality of P. bruesi Hershler & Sada, sp. nov. in Hualapai Flat (arrows). Map from USGS Hualapai
Flat South Quadrangle, 7.5 minute series (topographic). Foothills of the Granite Range are to the west, and theedge of the Hualapai playa is to the southeast.

Hualapai Flat has been technically active from the lateCenozoic through the Holocene, with both normal andlateral slip along several major fault zones (Grose, 1978;
Grose & Sperandio, 1978). Uplift of the Granite Rangeon the west side of the basin has been particularly rapid
and extensive (Bonham, 1969; Grose, 1978). Hualapai
Flat is bisected by a regional north-south fault zone which
extends from the High Rock area to the Pyramid Lakebasin (Grose, 1987). Occurrence of local hot spring activity is attributed to the intersection of this and another,northwest-trending fault zone, which permits deep penetration to a regional heat reservoir (Sperandio & Grose,1976). (Near-surface intrusive bodies are not sufficiently
hot to generate local geothermal activity.) Although individual springs in the Hualapai Flat may be no more thanLahontan in age, the supplying heat reservoir has been inplace for 2-20 my (Grose, 1978) which, together withlocally extensive faulting from mid-Tertiary into the Holocene, suggests that a long history of thermal spring activity in the area now occupied by this basin is feasible.

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C. T. 1928. Studies on the fauna of hot springs in thewestern United States and the biology of thermophilous animals. Proceedings of the American Academy of Arts andSciences 63(4): 139-228, pis. I-VI.
BRUES, C. T. 1932. Further studies on the fauna of North American hot springs. Proceedings of the American Academy ofArts and Sciences 67(7): 185-303.
GARSIDE, L. I. & J. H. SCHILLING. 1979. Thermal waters of Nevada. Nevada Bureau of Mines and Geology Bulletin 91:1163, 1 pi.
GROSE, L. T. 1978. Late Quaternary tectonic controls of occurrence of geothermal systems in Gerlach-Hualapai Flat area,
northwestern Nevada. Pp. 11-14 in G. V. Keller & L. T.
Grose (eds.), Studies of a Geothermal System in Northwestern Nevada, Part 1. Colorado School of Mines Quarterly
73(3).
GROSE, T. L. T. 1987. Major cxtcnsional tectonic intersection at
the Gerlach thermal area, northwestern Nevada. American
Geophysical Union Transactions 68(44): 1509-1510. (abstract)
GROSE, L. T & G. V. KELLER. 1975. The Colorado School ofMines Nevada Geothermal Study. [Unpublished] Progress
report [to the National Science Foundation] No. 4, for period
February 1-October 31, 1975. 109 pp.
GROSE, L. T. & R. I. SPERANDIO. 1978. Geology of the GerlachHualapai Flat geothermal area, northwestern Nevada. Pp. 1—
10 in G. V. Keller & L. T Grose (eds.), Studies of a Geothermal System in Northwestern Nevada, Part 1. Colorado
School of Mines Quarterly 73(3).
HERSHLER, R. 1994. A review of the North American freshwatersnail genus Pyrgulopsis (Hyrdobiidae). Smithsonian Contributions to Zoology 554:1-115.
HERSHLER, R. 1995. New freshwater snails of the genus Pyrgulopsis (Rissooidea: Hydrobiidae) from California. The Veliger 38(4):343-373.
HERSHLER, R. 1998. A systematic review of the hydrobiid snails(Gastropoda: Rissooidea) of the Great Basin, western UnitedStates. Part I. Genus Pyrgulopsis. The Veliger 41(1): 1—132.
HERSHLER, R. 1999. A systematic review of the hydrobiid snails(Gastropoda: Rissooidea) of the Great Basin, western UnitedStates. Part II. Genera Colligyrus, Eremopyrgus, Fluminicola, Pristinicola, and Tryonia. The Veliger 42(4):306-337.
HERSHLER, R. & W. F PONDER. 1998. A review of morphologicalcharacters of hydrobiid snails. Smithsonian Contributions to
Zoology 600:1-55.
HERSHLER, R. & D. W. SADA. In press. Biogeography of GreatBasin aquatic snails of the genus Pyrgulopsis. Smithsonian
Contributions to the Earth Sciences 33.
HOSE, R. K. & B. E. TAYLOR. 1974. Geothermal systems ofnorthern Nevada. United States Geological Survey OpenFile Report 74-271:1-27.
MALLIS, A. 1971. American Entomologists. 5. Rutgers University
Press: New Brunswick, New Jersey. 549 pp.
MIFFLIN, M. D. & M. M. WHEAT. 1971. Isostatic warping inLahontan basin, northwestern Great Basin. Geological Society of America Annual Meetings Abstracts with Programs
3(7):647.
MIFFLIN, M. D. & M. M. WHEAT. 1979. Pluvial lakes and estimated pluvial climates of Nevada. Nevada Bureau of Minesand Geology Bulletin 94:1-57, pi. I.
MLADENKA, G. C. 1992. The ecological life history of the Bruneau Hot Springs Snail (Pyrgulopsis bruneauensis). Final
Report to the United States Fish and Wildlife Service. 116
pages.
BRUES,

Figure 6
Type locality of P. bruesi Hershler & Sada, sp. nov. Granite
Range is in the background. Photograph, 19 July 1997.

A pre-Pleistocene origin of P. bruesi requires persistence of this snail through the time period when Lake
Lahontan flooded Hualapai Flat. Snails may have invaded
basinal habitats from higher elevation springs (following
desiccation of this lake) in conjunction with migrating
geothermal activity as mediated by local faulting. (Fossil
spring deposits attest to local migration of surface thermal
activity; Grose, 1978.) The possibility that basinal springs
harbored snails while covered by Lake Lahontan also
merits consideration.
Acknowledgments. We thank Y. Villacampa for assistance withscanning electron microscopy, K. Darrow for inking anatomical
drawings, M. Ryan for her drawing of the holotype and assemblyof plates, and D. Cole for preparing the map (all from USNM).
Fieldwork was supported, in part, by a 1997 award from the
National Museum of Natural History Biological Surveys and Inventories Program (BSI).

LITERATURE CITED
BONHAM, H. E

1969. Geology and mineral deposits of Washoeand Storey Counties, Nevada. Nevada Bureau of Mines andGeology Bulletin 70:1-140, pis. 1-6.

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M. C. 1996. Old, very high pluvial lake levels in theLahontan basin, Nevada: evidence from the Walker Lakebasin. United States Geological Survey Open-File Report
96-514:1-19.
REHEIS, M. C. & R. MORRISON. 1997. High, old pluvial lakes ofwestern Nevada. Pp. 459-492 in P. K. Link & B. J. Kowallis(eds.), Proterozoic to Recent Stratigraphy, Tectonics, andVolcanology, Utah, Nevada, Southern Idaho and Central
Mexico. Brigham Young University Geology Studies 42(1).
SINCLAIR, W. C. 1962. Ground-water resources of Hualapai Flat,
Washee, Pershing, and Humboldt Counties. State of Nevada
Department of Conservation and Natural Resources Groundwater Resources—Reconnaissance Series Report 11:1-15,
figs. 1-5, tables 1-4.
SPERANDIO, R. J. & L. T. GROSE. 1976. Tectonic controls on the
REHEIS,

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WALLACE, R. E. 1984. Patterns and timing of late Quaternaryfaulting in the Great Basin Province and relation to someregional tectonic features. Journal of Geophysical Research89(B7):5763-5769.
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