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Montana Field Guide

Montana Field Guides

Comb Snaggletooth - Gastrocopta pentodon
Other Names:  Vertigo pentodon, Pupa pentodon, Bifidaria pentodon, Pupa curvidens

Native Species

Global Rank: G5
State Rank: SNR

Agency Status

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General Description
A very small snail, to 1.1 mm diameter and 1.9 mm in height, subcylindrical (pupiform) and tapering, surface smooth, about 5 whorls. Shell coloration is translucent white. Aperture subovate, typically with 5 teeth (denticles: parietal, columellar, subcolumellar, lower palatal, upper palatal) but sometimes to 8 teeth, parietal tooth not shaped like the Greek letter lambda, columellar tooth not curving downward within the aperture, palatal callus present, sinulus absent, crest low to well developed, lip thin and slightly flared. Shape variable, more conical in wet localities (Hendricks 2012).

Diagnostic Characteristics
Shape (pupiform) and color (transparent whitish), with teeth in the aperture distinguish Gastrocopta from similar sized and shaped shells (Pupilla, Vertigo, Columella). G. armifera is the largest (height > 3.5 mm, diameter > 2.0 mm) with 6 teeth in aperture. Both G. holzingeri and G. pentadon are about 2.0 mm in height and 1.0 mm in diameter. G. holzingeri has a parietal tooth forked and shaped like the Greek letter lambda and a columellar tooth curving downward (basally) within aperture; the parietal tooth of G. pentodon is not lambda-shaped and the columellar tooth does not curve downward within the aperture.

Species Range
Montana Range


Range Comments
Eastern Canada and the United States west to Alberta, south to Florida, Arizona, New Mexico, Texas, into eastern Mexico and Guatemala. In Montana, reported on both sides of the Continental Divide from three counties: Lewis and Clark, Ravalli, Wibaux. Elevation range is 823 to 1829 m (2700 to 6000 ft). This species in Montana is probably referable to Gastrocopta tappeniana; true G. pentodon occurs west only to eastern North Dakota. Range and abundance in Montana are poorly understood; current status needs investigation (Hendricks 2012).

Observations in Montana Natural Heritage Program Database
Number of Observations: 5

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Relative Density



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

Not described for Montana. Forest canopy includes aspen and brushy hillsides, sometimes in openings. Found in leaf litter, moss, grass, or duff (Hendricks 2012).

  • Literature Cited AboveLegend:   View Online Publication
    • 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.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Forsyth, R.G. 2004. Land snails of British Columbia. Royal British Columbia Museum: Victoria, British Columbia, Canada. 188 pp.
    • Harris, S.A. 1978. Vertical zonation of land snails in the Iraqi slopes of the Persian Mountains and in the Rocky Mountains of Alberta, Canada. Arctic and Alpine Research 10:457-463.
    • Henderson, J. 1924. Mollusca of Colorado, Utah, Montana, Idaho, and Wyoming. University of Colorado Studies 13(2):65-223.
    • Nekola, J.C. and B.F. Coles. 2010. Pupillid land snails of eastern North America. American Malacological Bulletin, 28(2):29-57
    • Pilsbry, H.A. 1948. Land Mollusca of North America (north of Mexico), Volume II Part 2. The Academy of Natural Sciences of Philadelphia Monograph Number 2(2): 521-1113.
    • Squyer, H. 1894. List of shells from the vicinity of Mingusville, Montana. The Nautilus 8:63-65.
    • Sterki, V. 1890b. On Some Northern Pupidae, with Descriptions of New Species. The Nautilus 3:123-126.
    • Vanatta, E.G. 1914. Montana shells. Proceedings of the Academy of Natural Sciences of Philadelphia 66:367-371.
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Citation for data on this website:
Comb Snaggletooth — Gastrocopta pentodon.  Montana Field Guide.  .  Retrieved on , from