Tryonia metcalfi 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 metcalfi

description: Tryonia metcalfi sp. nov.
(Figs 5 I, 9E–F, J–K, O –Q)
Types. Holotype, USNM 1001931, unnamed seeps in La Cienega, ca. 0.8 km east of cemetery, Presidio County, Texas, 30º6'38.9" N, 104º40'21.1" W, leg. R.H. and J.J.L., 6/xii/2001. Paratypes (from same lot), USNM 1153672.
Etymology. A patronym honoring Art Metcalf (University of Texas at El Paso, now retired) for his many years of study of regional mollusks and for the unfailing encouragement and support that he provided to other such researchers.
Referred material. TEXAS. Presidio County. USNM 1151243, topotypes, J.J.L., 15/ii/2011.
Diagnosis. Shell medium-sized, ovate-conic; penis having two distal and two basal papillae on the inner edge. Distinguished from Chihuahuan Desert congeners by the greatly enlarged size of the penial papillae relative to the penis. Further differentiated from lower Río Conchos basin congeners by having a basal papilla on the inner edge of the penis, and from Pecos River basin congeners by its larger penial stylet.
Description. Shell (Fig. 9 E–F) up to 2.6 mm tall, large females having 4.5–5.0 whorls, spire height 100–130% width of shell, sexual dimorphism of shells not obvious. Teleoconch whorls medium convex, shouldered, sutures impressed. Aperture ovate, inner lip complete, slightly thickened, adnate or disjunct, umbilicus narrow or absent. Outer lip thin, orthocline. Sculpture of strong growth lines. Periostracum tan, usually absent owing to erosion of shell surface.
Shell measurements (mean in parentheses): height 1.99–2.62 mm (2.24), width 1.08–1.34 mm (1.19), body whorl height 1.34–1.66 mm (1.51), body whorl width 0.99–1.27 mm (1.12), aperture height 0.77–0.97 mm (0.87), aperture width 0.67–0.80 mm (0.73), total number of whorls 4.50–5.00 (4.78) (USNM 1153672, n = 10).
Measurements of holotype: height 2.27 mm, width 1.17 mm, body whorl height 1.52 mm, body whorl width 1.12 mm, aperture height 0.89 mm, aperture width 0.73 mm, 4.75 whorls.
Inner and outer sides of operculum smooth (Fig. 9 J–K). Radula (Fig. 9 O –Q): dorsal edge of central radular teeth strongly concave, basal tongue V-shaped, median cusps distally pointed, parallel-sided proximally, lateral cusps five–seven, basal cusps one–two (innermost larger) (Fig. 9 P). Lateral teeth having four–six cusps both on the inner and outer sides, length of outer wing about 160% width of cutting edge, central cusp pointed (Fig. 9 Q). Inner marginal teeth having 24–28 cusps, outer marginal teeth having 26–32 cusps. Radula data are from USNM 1153672.
Animal darkly pigmented. Penis (Fig. 5 I) having two distal and two basal papillae on the inner edge (30/ 30 specimens), the basal-most papilla is sometimes positioned partly on the dorsal surface. Distal bulb of penis expanded laterally on inner side, black; stylet large. Penial duct weakly undulating in medial section. Penial data are from USNM 1151243.
Distribution and habitat. Endemic to a single locality along the east side of the Rio Grande above the mouth of the Río Conchos (Figure 1, locality 12). This locality is a complex of small seeps that discharges into a broad arroyo (Fig 6 K). Tryonia metcalfi was found on mud, decaying vegetation and on the undersides of rocks in 19°C water. This habitat has been heavily degraded by livestock.
Remarks. Tryonia metcalfi was delineated as a well supported lineage in the Bayesian tree (Fig. 2). This species was discovered coincidentally while searching for additional localities for Pyrgulopsis metcalfi (Taylor, 1987), which is distributed a little to the south of La Cienega (Taylor 1987).
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 19-21, DOI: 10.5281/zenodo.278442