Montana Field Guide

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.

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).

Non-migratory.

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).

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.

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

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).