Hendersonia occulta (Say, 1831), the Cherrystone Drop Snail (Gastropoda: Helicinidae), extended geographic distribution, Wisconsin, USA

Abstract

This paper describes a range extension of Hendersonia occulta, the cherrystone drop snail. This species, occurring in heavily wooded areas with carbonate geology, is imperiled in Wisconsin. Prior to our research, H. occulta had been found in 13 counties within Wisconsin, mostly in the southwestern and eastern parts of the state. We have found 13 new populations, both within counties where the snail was known to occur, and within three new counties, representing a ~150 km range extension northward.

Episodic deposition of Illinois Valley Peoria silt in association with Lake Michigan Lobe fluctuations during the last glacial maximum

“…The modern habitats of late Pleistocene gastropod assemblages identified from the New Cottonwood School and Thomas Quarry sections suggests these areas were forested at the time of loess deposition (Baker, 1939; Leonard and Frye, 1960; Nekola and Coles, 2010). For example, H. occulta relies on deep leaf litter in undisturbed woodlands (Lynum et al, 2013). The occurrence of boreal to arctic snails, C. alticola and V. modesta, immediately above the Jules Geosol at New Cottonwood School is indicative of relatively colder environments.…”