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A Review of the North American Freshwater Snail Genus Pyrgulopsis

A Review of the North American Freshwater Snail Genus Pyrgulopsis

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NUMBER 554 23<br />

DISTRIBUTION.—This presumably extinct species apparently<br />

was endemic to <strong>the</strong> type locality, which occurs in <strong>the</strong> portion <strong>of</strong><br />

northwest Chihuahua known as <strong>the</strong> "Guzmdn complex,"<br />

comprising <strong>the</strong> terminus <strong>of</strong> Rfos Mimbres, Casas Grandes,<br />

Santa Maria, and del Carmen (Miller, 1978,1981). The springs<br />

at Las Palomas dried during <strong>the</strong> 1970s (Jerry Landye, pers.<br />

comm., 1992).<br />

REMARKS.—This snail is united with P. bruneauensis by<br />

unique synapomorphies <strong>of</strong> a complex oviduct coil (51-2) and<br />

anterior position <strong>of</strong> seminal receptacle relative to oviduct coil<br />

(61-1). <strong>Pyrgulopsis</strong> brandi differs by its stronger operculum<br />

attachment scar, larger terminal gland, and elongate seminal<br />

receptacle duct.<br />

MATERIAL EXAMINED.—UMMZ uncat. (M50-8), springfed<br />

pond 3.6 mi. (5.8 km) south <strong>of</strong> Las Palomas. This is almost<br />

certainly <strong>the</strong> type locality (despite <strong>the</strong> discrepancy with Drake's<br />

data) as only a single spring has been known historically from<br />

<strong>the</strong> area (J. Landye, pers. comm., 1992).<br />

<strong>Pyrgulopsis</strong> bruneauensis Hershler, 1990<br />

<strong>Pyrgulopsis</strong> bruneauensis Hershler, 1990:803—USDI, 1993:5938.<br />

<strong>Genus</strong> and species undescribed.—USDI, 1991b:58818.<br />

DIAGNOSIS.—Shell globose to broadly conical, mediumsized,<br />

umbilicate. Penial filament elongate, lobe very short<br />

Penial ornament a small, weakly developed terminal gland<br />

DESCRIPTION.—Shell (Figure 10a) globose to broadly<br />

conical; height, 2.2-2.9 mm; whorls, 3.75-4.25. Early<br />

protoconch weakly punctate adapically, o<strong>the</strong>rwise near smooth<br />

(<strong>of</strong>ten eroded). Teleoconch whorls convex, shouldered; sculpture<br />

<strong>of</strong> moderately pronounced growth lines. Aperture broadly<br />

ovate, large, very narrowly adnate or (more commonly) slightly<br />

separated from body whorl. Inner lip complete, thick. Outer lip<br />

prosocline. Umbilicus rimate to broadly perforate. Periostracum<br />

light amber.<br />

Operculum (Figure l0b,c) ovate, amber, nucleus slightly<br />

eccentric; dorsal surface weakly frilled. Attachment scar<br />

weakly thickened along inner edge near nucleus, very faint<br />

o<strong>the</strong>rwise; callus a very weak, narrow thickening near inner<br />

edge.<br />

Central radular tooth (Figure 33c) with moderately indented<br />

dorsal edge; lateral cusps, 4-6; central cusp pointed, slightly<br />

broader and considerably longer than laterals; basal cusps, 1,<br />

narrowly triangular, with very weak dorsal support Basal<br />

process broad, tongue-like; basal sockets deep. Lateral margins<br />

thickened; neck pronounced.<br />

Snout dark brown-black; cephalic tentacles similarly pigmented,<br />

although pale around eyespots. Foot pigment moderate-dark,<br />

especially along anterior edge. Opercular lobe black<br />

along sides, with internal black granules concentrated along<br />

inner edge. Neck pigment light-moderate, <strong>of</strong>ten with central<br />

pale area extending to foot Pallial ro<strong>of</strong>, visceral coil dark,<br />

near-uniformly pigmented.<br />

Ctenidial filaments, 20, tall, narrow. Osphradium centered<br />

posterior to middle <strong>of</strong> ctenidial axis. Kidney opening slightly<br />

thickened. Stomach caecum very small.<br />

Testis, 1 whorl, overlapping posterior stomach chamber.<br />

Prostate gland with large (32%) pallial section; pallial vas<br />

deferens proximally kinked. Penis (Figure 44c) medium to<br />

large-sized; filament elongate (about twice as long as base),<br />

muscular, little tapered; lobe very short, slightly tapered<br />

distally. Terminal gland small (sometimes very reduced or<br />

absent), variably shaped, borne along distal edge, usually in<br />

ventral position. Filament very dark (internal pigment).<br />

Female genitalia shown in Figure 5a. Ovary, 0.75 whorl,<br />

overlapping posterior stomach chamber. Pallial albumen gland<br />

large (25%). Capsule gland as long as albumen gland. Genital<br />

aperture a subterminal slit (slightly raised and thickened) with<br />

vestibule. Coiled oviduct usually <strong>of</strong> three loops (vertical,<br />

posterior oblique, horizontal). Oviduct and bursal duct join<br />

slightly behind pallial wall. Bursa copulatrix ovoid, medium<br />

length and width, with about half <strong>of</strong> length posterior to gland.<br />

Bursal duct medium width, about as long as bursa copulatrix.<br />

Seminal receptacle stout, short, with short duct pressed against<br />

middle loop <strong>of</strong> coiled oviduct, usually overlapping anterior<br />

bursa copulatrix or proximal section <strong>of</strong> bursal duct<br />

TYPE LOCALITY.—Spring along west side <strong>of</strong> Bruneau River,<br />

about 100 m downflow from Hot Creek's confluence with <strong>the</strong><br />

river, Owyhee County, Idaho (T 7S, R 6E, SW1/4 sec. 34).<br />

Holotype, USNM 860507; paratypes, USNM 860508.<br />

DISTRIBUTION.—Small springs along Hot Creek and confluent<br />

Bruneau River, Owyhee County, Snake-Columbia River<br />

basin.<br />

MATERIAL EXAMINED.—USNM 860508 (paratypes).<br />

<strong>Pyrgulopsis</strong> bryantwalkeri, new name<br />

Fluminicola nevadensis Walker, 1916:6 [unlabeled figure, p. 6 (not Pyrgula<br />

nevadensis Steams, 1883)]; 1918:142.—Turgeonetal., 1988:60.<br />

"Fluminicola" nevadensis.—Taylor, 1975:127.<br />

DIAGNOSIS.—Shell globose to ovate-conic, small to medium-sized,<br />

umbilicate. Penial filament short, lobe very weak.<br />

Penial ornament a weakly developed terminal gland.<br />

DESCRIPTION.—Shell (Figure lOd) globose to ovate-conic;<br />

height 1.5-3.2 mm; whorls, 3.5-4.5. Protoconch moderately<br />

punctate, although weaker near beginning <strong>of</strong> teleoconch.<br />

Teleoconch whorls moderate to highly convex, shouldered;<br />

body whorl sometimes with weak angulation at or near<br />

periphery; sculpture <strong>of</strong> weak to strong growth lines. Aperture<br />

broadly ovate, angled above, usually separated (sometimes<br />

greatly so) from body whorl. Inner lip complete, thickened;<br />

columellar region narrowly excavated. Outer lip prosocline.<br />

Umbilicus deeply perforate. Periostracum brown.<br />

Operculum (Figure 10e,/) broadly ovate, dark amber,

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