Tryonia molinae Hershler, Liu & Landye, 2011, sp. nov.
Creators: name: Hershler, Robert
name: Liu, Hsiu-Ping
name: Landye, Jerry
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Hydrobiidae
Tryonia
Tryonia molinae

description: Tryonia molinae sp. nov.
(Figs 5 E, 8A–C, G–H, K–M)
Types. Holotype, USNM 1139278, unnamed spring in northern part of El Molino, ca. 125 m east of Chihuahua Highway 15, Chihuahua, 29º12'11" N, 107º24'24" W, leg. J.J.L., 26/iv/2010. Paratypes (from same lot), USNM 1153674.
Etymology. A geographical epithet referring to El Molino.
Diagnosis. Shell medium-sized, elongate-conic; penis having two distal and one basal papillae on the inner edge. Differentiated from closely similar T. taylori (described below) by having a single basal papilla on the inner edge of the penis.
Description. Shell (Fig. 8 A–C) up to 3.9 mm tall, large females having 4.75–6.25 whorls, spire height 133–167% width of shell, male shells smaller than those of females. Teleoconch whorls weak to medium convex, evenly rounded, with impressed sutures. Aperture weakly angled and sometimes slightly thickened adapically, parietal lip complete, sometimes thickened, adnate, umbilicus narrow. Outer lip orthocoline or weakly prosocline. Sculpture of strong growth lines and weak spiral threads. Periostracum tan.
Shell measurements (mean in parentheses): height 2.84–3.92 mm (3.35), width 1.35–1.77 mm (1.54), body whorl height 1.70–2.04 mm (1.85), body whorl width 1.25–1.63 mm (1.44), aperture height 0.96–1.19 mm (1.06), aperture width 0.79–0.96 mm (0.87), total number of whorls 4.75–6.25 (5.73) (USNM 1153674, n = 10).
Measurements of holotype: height 3.26 mm, width 1.55 mm, body whorl height 1.90 mm, body whorl width 1.48 mm, aperture height 1.05 mm, aperture width 0.90 mm, 5.75 whorls.
Inner and outer sides of operculum smooth (Fig. 8 G–H). Radula (Fig. 8 K-M): dorsal edge of central radular teeth concave, basal tongue V-shaped, median cusps elongate, distally pointed or jagged-edged, parallel-sided proximally, lateral cusps four–seven, basal cusps two–three (innermost larger) (Fig. 8 L). Lateral teeth having two–six cusps on inner and three–six cusps on outer side, length of outer wing 167–200% width of cutting edge, central cusp pointed or jagged-edged (Fig. 8 M). Inner marginal teeth with 19–31 cusps, outer marginal teeth with 27–35 cusps. Radula data are from USNM 1153674.
Animal darkly pigmented. Penis (Fig. 5 E) having two distal and one basal papillae on the inner edge (30 of 30 specimens examined). Basal papilla often small, sometimes positioned ventrally near inner edge. Distal bulb of penis expanded laterally on inner side, lightly pigmented; stylet small. Penial duct nearly straight. Penial data are from USNM 1153674.
Distribution and habitat. Tryonia molinae is endemic to a single locality in the Río Santa Maria basin (Fig. 1, locality 6) that is locally known as “El Ojo.” The outflow of this thermal (28°C) spring is ponded by a small retention dam and used for recreation (Fig. 6 E). Snails were abundant on all substrates (including rocks, rootlets and algae) in the headspring and upper portion of the pool.
Remarks. Tryonia molinae was delineated as a well supported lineage in the Bayesian analysis (Fig. 2).
description: Published as part of Hershler, Robert, Liu, Hsiu-Ping & Landye, Jerry, 2011, New species and records of springsnails (Caenogastropoda: Cochliopidae: Tryonia) from the Chihuahuan Desert (Mexico and United States), an imperiled biodiversity hotspot, pp. 1-32 in Zootaxa 3001 on pages 15-16, DOI: 10.5281/zenodo.278442