Tryonia infernalis Hershler, Liu, & Simpson

Hershler, Robert, Liu, Hsiu-Ping & Simpson, Jeffrey S., 2015, Assembly of a micro-hotspot of caenogastropod endemism in the southern Nevada desert, with a description of a new species of Tryonia (Truncatelloidea, Cochliopidae), ZooKeys 492, pp. 107-122 : 112-114

Taxon classification Animalia Littorinimorpha Cochliopidae

Tryonia infernalis Hershler, Liu, & Simpson sp. n.

Tryonia infernalis Undescribed [ Fontelicella and] Tryonia species.- Williams et al. 1985: 32.

Tryonia porrecta .- Hershler 1999: 335.

Types.

USNM 883884 (a dry shell), Blue Point Spring, just below source, Clark County, Nevada, 36.3894°N, 114.4329°W, 24 July 1988, R. Hershler. Paratypes (ca. 200 dry shell and alcohol preserved specimens), USNM 1266143 (from same lot).

Referred material.

NEVADA. Clark County: USNM 883248 (coll. James J. Landye, 17-XII-1992), USNM 1098627 (coll. Donald W. Sada, 6-XII-2006), USNM 1146345 (coll. Andrew K. Schwaneflugel, 29-V-2008), USNM 1146420 (coll. DWS, 11-XII-2009), USNM 1248362 (coll. RH, 5 –15– 2014), USNM 854844 (coll. Saxon Sharpe, no date), Blue Point Spring.

Diagnosis.

Shell medium-sized, conic to turriform; penis having two distal papillae on the inner edge and a single basal papilla both on the inner and outer edges. Readily distinguished from geographically proximal and closely related Tryonia clathrata by its smaller size, weaker shell sculpture, and smaller number of papillae on the inner edge of the penis. Differentiated from Tryonia gilae (also distributed in the lower Colorado River basin) by its more convex teleoconch whorls, lateral expansion of distal bulb of penis, and in having a basal papilla on the inner edge of the penis. Differs from Tryonia porrecta , with which it was previously confused, by its smaller size, consistently weak shell sculpture, and much greater frequency of males.

Description.

Shell (Fig. 4 A–B) up to 2.8 mm tall, large females having 5.00-5.75 whorls, spire height 100-133% width of shell, male shells smaller than those of females. Teleoconch whorls highly convex, evenly rounded. Aperture ovate, weakly angled adapically. Parietal lip complete, adnate, umbilicus narrow. Outer lip orthocline or prosocline, sometimes weakly sinuate. Sculpture of strong growth lines and a few weak spiral threads. Periostracum light brown. Shell parameters for a series of paratypes are given in Table 1.

Inner and outer sides of operculum smooth (Fig. 4 C–D). Radula (Fig. 4 E–G): dorsal edge of central teeth concave, basal tongue V-shaped, median cusps elongate, distally pointed, lateral cusps four–six, basal cusps one–two, usually two (innermost larger; Fig. 4F). Lateral teeth having three–five cusps on inner and five–seven cusps on outer side, length of outer wing about 200% width of cutting edge, central cusp pointed (Fig. 4G). Inner marginal teeth with 24-34 cusps, outer marginal teeth with 27-38 cusps. Radula data are from USNM 1266143.

Animal darkly pigmented. Penis (Fig. 5) having two distal and one basal papillae on inner edge and one basal papilla on outer edge (29 of 30 specimens); one specimen differed in having a single distal papilla along the inner edge. Distal bulb of penis expanded laterally on inner side, black; stylet small. Penial duct weakly undulating along most of length. Penial data are from USNM 1248362.

Etymology.

The specific epithet (infernalis) is a Latin adjective meaning hellish, and refers to the Valley of Fire, which is closely proximal to the type locality.

Distribution and habitat.

Tryonia infernalis is known only from its type locality, a thermal (ca. 30 °C) rheocrene (discharging ca. 0.55 l/s; USGS 2007) whose outflow forms a narrow (ca. 0.3 m) stream (Fig. 6A). Tryonia infernalis is restricted to the upper 10 m of the spring run where it lives on silt and rocks. This species was considered to be extinct in 2002 following a series of unsuccessful searches, however it was subsequently “rediscovered” in a small, ponded reach above a weir plate associated with a USGS gaging station (Fig. 6B) in 2007 ( Sada and Jacobs 2008; also see CCDCP 2002) and currently is abundant at this site (RH, personal observation).

Remarks.

The reproductive anatomy of several females was studied to confirm that this species belongs to Tryonia as currently defined ( Hershler 2001).