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Gallatin Mountainsnail - Oreohelix yavapai mariae

Species of Concern

Global Rank: G5T1
State Rank: S1

Agency Status


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General Description
Bartsch (1916) describes the shell as “decidedly depressed helicoid, almost lenticular, flesh colored, with a narrow brown band on the upper surface, which is a little nearer the peripheral cord than the suture, and a second even narrower one bordering the peripheral cord on the lower surface. Nuclear whorls scarcely differentiated from succeeding turns, bearing the same sculpture as the adult whorls, but a little less strongly expressed. Periphery of the whorls provided with a cord-like keel, which becomes somewhat weakened on the last quarter of the last turn. Entire surface both above and below marked by slender thread-like incremental lines and fine spiral striations; last whorl slightly descending near the aperture. Base broadly, openly umbilicated, well rounded; a little more convex at the umbilical wall than at the lateral margin. Aperture very oblique, oval; peristome neither thickened nor reflected at the edge; parietal wall strong, rendering the peristome complete” (p. 331). Shell diameter 20.7 mm (18.3-22.5 mm; n = 9); shell height 9.2 mm (8.2-10.0 mm; n = 9); number of whorls 5.5 (5.2-5.6; n = 9). Internal anatomy not described.

Taxonomic Comment: The original description of this taxon by Bartsch (1916) and his placement as a subspecies of Oreohelix yavapai are still valid. Pilsbry (1939) noted the larger size of this form, but thought separation of this subspecies may prove difficult or impracticable. Frest and Johannes (1995) consider this taxon distinct from another subspecies, O. yavapai extremitatis, that is present in the Big Horn Mountains, Wyoming, and the nearby Bridger Range, Montana, noting the consistent larger size of O. y. mariae, more evident pigmented banding, less extreme carination and a less-deflected aperture. Pilsbry (1939) placed all Oreohelix in the Xanthonycidae.

Active in wet and cool weather; otherwise not described.

Diagnostic Characteristics
A combination of shell shape (broadly heliciform or somewhat flattened), small size, opaque shell color (especially chalky white when dead) with a few bands, absence of reflected lip, and absence of teeth in the aperture distinguishes this from other Montana land snails (Hendricks 2003, 2012). Most other large species of Oreohelix in Montana are less flattened and less carinate (keeled) or else show stronger ribbing (e.g., O. elrodi). Oreohelix yavapai mariae is probably best differentiated in Montana by range and habitat, but also distinguished from other forms of O. yavapai by its larger size, less carinate shell, less deflected aperture, and more evident pigmentation and banding (Frest and Johannes 1995; Burke 2013).

Species Range
Montana Range

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Range Comments
Montana endemic: known only from the type locality at Storm Castle Creek (formerly Squaw Creek) near the mouth of Gallatin Canyon in the Gallatin Range, Gallatin County (presumably above the confluence of Squaw Creek with the Gallatin River) at 1707 m (5600 ft) elevation (Bartsch 1916; Burke 2013). Six live animals and 50 shells documented at the site as recently as 2009 (see O. yavapai account in Hendricks 2012).

Summary of Observations Submitted for Montana
Number of Observations: 6

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Predicted Distribution in Montana
Predicted distribution model for Gallatin Mountainsnail (Oreohelix yavapai mariae). Records were spatially unique and had a locational uncertainty of ≤ 400 meters.  Hotter colors indicate areas that are predicted to have more suitable habitat for the species.  Black dots are positive data used to build the model.  Gray dots are locations where a survey capable of detecting the species has been performed.  Landownership, a shaded relief map, and county lines are included for reference.  Details of the modeling effort, a description of the environmental layers used, and a more thorough interpretation of model outputs can be found in the report Land Mollusk Surveys and Predicted Distribution Models on USFS Northern Region Lands: 2007.

Predicted Distribution Map

More model output for this species

Present on a south-facing slope in grassy habitat around and below limestone outcroppings. Shells found in the open, some live individuals attached to limestone rocks imbedded in loose soil under scattered Rocky Mountain juniper and Douglas-fir, and scattered bunch grasses, on an steep, exposed slope (see O. yavapai account in Hendricks 2012).

Food Habits
Not described.

Little information. Live animals have been documented at the type locality as recently as August 2009, attached and estivating on limestone rocks or near the base of scattered trees. Population trends are unknown, but the species persists at the type locality.

Reproductive Characteristics
Presumably hermaphroditic, but the internal anatomy, as well as other reproductive characteristics, not described.

Threats or Limiting Factors
Logging and road construction along the Gallatin River and Squaw Creek are likely the main threats that could impact the only known population (Frest and Johannes 1995). Fire, fire suppression, weed control, and grazing could also have negative impacts (Hendricks 2003).

  • Literature Cited AboveLegend:   View Online Publication
    • Bartsch, P. 1916. Two new land shells from the Western States. Proceedings of the U. S. National Museum 51:331-333.
    • Burke, T. E. 2013. Land snails and slugs of the Pacific Northwest. Corvallis, OR: Oregon State University Press. 344 p.
    • Frest, T.J. and E.J. Johannes. 1995. Interior Columbia Basin mollusk species of special concern. Final report to the Interior Columbia Basin Ecosystem Management Project, Walla Walla, WA. Contract #43-0E00-4-9112. 274 pp. plus appendices.
    • Hendricks, P. 2003. Status and conservation management of terrestrial mollusks of special concern in Montana. Unpublished report prepared for the U.S. Forest Service. Montana Natural Heritage Program, Helena, Montana. 67 pp. + appendices.
    • Hendricks, P. 2012. A Guide to the Land Snails and Slugs of Montana. A report to the U.S. Forest Service - Region 1. Montana Natural Heritage Program, Helena, MT. vii + 187 pp. plus appendices.
    • Pilsbry, H.A. 1939. Land Mollusca of North America (north of Mexico.) George W. Carpenter Fund for the Encouragement of Original Scientific Research, Philadelphia, Pennsylvania. 2107 pp.
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Citation for data on this website:
Gallatin Mountainsnail — Oreohelix yavapai mariae.  Montana Field Guide.  .  Retrieved on , from