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Montana Field Guide

Montana Field Guides

Top-heavy Column - Pupilla syngenes
Other Names:  Pupa syngenes


Global Rank: G4
State Rank: SNR

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General Description
A small shell, to about 1.7 mm diameter and 4.0 mm in height, subcylindircal (pupiform) and barely tapering with a top-heavy profile, surface dull with fine axial striae, 8 or 9 whorls, the last compressed and flattened around the lower portion; usually sinistral (coiling to the left from the aperture). Shell coloration is reddish-brown. Aperture subovate, with a single small tooth (denticle: parietal), a blunt columellar tooth may be evident beyond the aperture, a small palatal tooth well within the aperture, crest prominent, lip flared. Occurs at some locations in both dextral (coiling to the right from the aperture) and sinistral (coiling to the left from the aperture) forms (Hendricks 2012).

The subspecies in Montana is Pupilla syngenes syngenes.

Diagnostic Characteristics
Pupilla are brownish shells with teeth or internal baffles, and possess an external crest behind the aperture (unlike Columella). The palatal lip is not indented, mature shells have 6-9 wholrls, the combination of which separates Pupilla from similar shaped and sized pupiform shells (Verigo). Absence of teeth in aperture distinguish Pupilla muscorum and P. hebes from P. syngenes and P. blandi. P. blandi similar to P. syngenes but mature shells with three teeth of about equal size in aperture (instead of one to three teeth all of which are relatively small), with right-curving whorls (instead of left-curving), 6-7 whorls (rather than 8-9 whorls), and shell lacking a top-heavy profile as in P. syngenes.

Species Range
Montana Range

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Range Comments
Native to the southwest (Utah, Colorado, Arizona, New Mexico) and north to Montana. In Montana, reported east of the Continental Divide from Wibaux County; elevation 823 m (2700 ft). Drift material (dead shells) may constitute the single Montana record, when 8 shells were reported. Range and abundance in Montana poorly documented; current status needs investigation (Hendricks 2012).

Summary of Observations Submitted for Montana
Number of Observations: 1

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

Recency

 

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



Habitat
Not described for Montana (Hendricks 2012). Well-drained hillsides in arid country, not under dense forest canopy; found among grass and under rocks.

References
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Citation for data on this website:
Top-heavy Column — Pupilla syngenes.  Montana Field Guide.  .  Retrieved on , from