Discus patulus
Domed disc

Key Characteristics

The domed disc snail is a small land snail 7 - 8 mm in width with a brown helicoid shell (low, flattened spirals) marked by relatively large, prominent ribs and a wide umbilicus (central opening on the base of the shell) that is over 1/2 the shell diameter.

Status and Rank

  • State Status: SC
  • State Rank: S1S2
  • Global Rank: G5

Occurrences

County NameNumber of OccurrencesYear Last Observed
Cass22002
Jackson11970
Washtenaw11970
Distribution map for Discus patulus

Updated 7/21/2017. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

This species is found under logs and moist leaves in upland deciduous forests, ravines, and river valleys. Rotting logs with loosened bark apparently provide optimal habitat.

Specific Habitat Needs

Downed woody debris needed in Floodplain forest, Mesic southern forest

Natural Community Types

Methodology

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management

Land-use activities that remove forest canopy cover and alter critical habitat requirements such as microclimate and moisture availability should be avoided at occupied sites. These include activities such as timber harvesting, residential development, and road building. The species also is sensitive to excessive trampling and ORV use.

Active Period

Active from first week of April to fourth week of September

Survey Methods

Surveys can be conducted anytime during the growing season, but are most successful in spring and fall following rain showers or when the soil is moist, and during higher relative humidity conditions and cooler temperatures. Visual surveys consist of looking for individuals crawling on the ground, in moist leaf litter, and on or under woody debris. Litter sampling consists of collecting soil and leaf litter samples in the field and drying, sifting and looking for snail shells in the litter samples in the laboratory.

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Jul 22, 2017]

References

Survey References

Technical References

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