Tryonia oasiensis 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 oasiensis

description: Tryonia oasiensis sp. nov.
(Figs 5 N, 12A–B, F–G, J–L)
Types. Holotype, USNM 1123759, Caroline Spring, upper reach of outflow of lower-most pond, Terrell County, Texas, 30º28'2.2" N, 101º48'6.6" W, leg. R.H. and J.J.L., 30/iii/2009. Paratypes (from same lot; 12 dry shells and 15 alcohol-preserved animals), USNM 1153675.
Etymology. The specific epithet refers to the distribution of this snail on the Oasis Ranch.
Diagnosis. Shell medium-sized, conic; penis having two distal papillae on the inner edge and a basal papilla on the outer edge. Distinguished from its two Pecos River basin congeners by its less convex teleoconch whorls and smooth inner side of the operculum. Further differentiated from T. cheatumi (Pilsbry, 1935) in having a basal papilla on the inner edge of the penis, broader central radular teeth, and longer outer wing of the lateral radular teeth; and from T. circumstriata (Leonard & Ho, 1960) in having weaker spiral sculpture on the teleoconch whorls and lacking a basal papilla on the inner edge of the penis.
Description. Shell (Fig. 12 A–B) up to 3.4 mm tall, large females having 6.25–6.50 whorls, spire height about 180% width of shell, male shells smaller than those of females. Teleoconch whorls weak convex, evenly rounded, sutures adpressed. Aperture ovate, adapically angled, inner lip complete, thin, adnate, umbilicus narrow or absent. Outer lip thin, orthocline or weakly prosocline. Sculpture of strong growth lines and, in some specimens, weak spiral threads. Periostracum tan.
Measurements of holotype: height 3.52 mm, width 1.40 mm, body whorl height 1.89 mm, body whorl width 1.36 mm, aperture height 0.97 mm, aperture width 0.81 mm, 6.25 whorls.
Outer side of operculum smooth or having edges of last 0.25 operculum whorl weakly frilled (Fig. 12 F); inner side of operculum smooth (Fig. 12 G). Radula (Fig. 12 J-L): dorsal edge of central radular teeth weakly concave, basal tongue rounded, median cusps pointed, lateral cusps four–six, basal cusps two–four (innermost larger) (Fig. 12 K). Lateral teeth having three–five cusps on both inner and outer sides, length of outer wing about 200% width of cutting edge, central cusp pointed (Fig. 12 L). Inner marginal teeth having 15–25 cusps, outer marginal teeth having 24–36 cusps. Radula data are from USNM 1153675.
Animal darkly pigmented. Penis (Fig. 5 N) having two distal papillae on inner edge and a basal papilla on outer edge (15 of 18 specimens), one specimen differed in having three distal papilla on inner edge, one specimen differed in having a (very small) basal papilla on the inner edge, and one specimen differed in lacking a papilla on the outer 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 1153675.
Distribution and habitat. Endemic to a single site in the lower Pecos River basin (Fig. 1, locality 13). This complex of large springs, which is also known as T5 Springs (Brune 1981), discharges into two large ponds which have been used for recreational purposes (Karges 2003). Tryonia oasiensis was found in low abundance (in silt) along the edges of a short (ca. 5 m) reach of the outflow of the lower pond (Fig. 6 P); the water temperature was 20°C. This species could not be found during two subsequent visits to the site in 2011. The status of T. oasiensis is uncertain because we have not carefully searched for it in the two ponds; there is no suitable habitat further downflow from the type locality. The ranch, on which these springs are situated, was purchased by The Nature Conservancy in 2000 (Karges 2003).
Remarks. Tryonia oasiensis was delineated as a well supported lineage in the Bayesian tree (Fig. 2). This species was discovered coincidentally during a visit to Oasis Ranch to collect other freshwater snails (Hershler et al. 2010). We did not obtain shell measurements for T. oasiensis (aside from the holotype) because our single sample was very small and most of the specimens were highly eroded.
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 26-27, DOI: 10.5281/zenodo.278442