Pyrgulopsis ventricosa


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Pyrgulopsis ventricosa
Species Authority: Hershler, 1995
Common Name(s):
English Clear Lake Pyrg
Pomatiopsis intermedia Cooper, 1876

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv) ver 3.1
Year Published: 2012
Date Assessed: 2012-03-05
Assessor(s): Cordeiro, J. & Perez, K.
Reviewer(s): Bohm, M., Collen, B. & Seddon, M.
Contributor(s): Dyer, E., Soulsby, A.-M., Whitton, F., Kasthala, G., McGuinness, S., Milligan, HT, De Silva, R., Herdson, R., Thorley, J., McMillan, K., Collins, A., Offord, S., Duncan, C. & Richman, N.
Pyrgulopsis ventricosa has been assessed as Critically Endangered under criterion B1ab(i,ii,iii,iv) and B2ab(i,ii,iii,iv) due to its restricted distribution with an extent of occurrence of 17 km2 and an area of occupancy which is less than 10 km2. It had a historically more widespread distribution but is now only found in one location and continues to be impacted by water loss, diversion and development. This is causing continuing declines in extent of occurrence, area of occupancy, habitat quality and number of subpopulations.

Geographic Range [top]

Range Description: This species is restricted to the Seigler Creek drainage in the south end of the Clear Lake basin, in California (Hershler 1995). Its extent of occurrence is estimated as less than 20 km2 and its area of occupancy is likely to be less than 10 km2.
United States (California)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species was commonly found in the stream where it is endemic, although historical records suggest as recently as 1970 it was more widespread in the Clear Lake region (Hershler 1995).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This species inhabits springs and small spring-fed streams, where it is found on vegetation (Hershler 1995).
Systems: Freshwater

Use and Trade [top]

Use and Trade: This species is not utilised.

Threats [top]

Major Threat(s): The only locality of this species, a small spring-fed stream, has been diverted and additionally impacted by human activities (Hershler 1995). Due to its highly restricted distribution, this snail is in danger of extinction from even minor alterations to its habitat.

Conservation Actions [top]

Conservation Actions: This species has a Global Heritage Status of G1 - Critically Imperilled (NatureServe 2009). Due to its highly restricted nature, protection of both this species and its habitat is essential to the continuing viability of the known population(s).

Citation: Cordeiro, J. & Perez, K. 2012. Pyrgulopsis ventricosa. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 27 August 2015.
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