With a few exceptions, the Viviparidae are characterised by medium high-spired shells with moderately to strongly inflated whorls that are often more or less circular in cross-section and separated by deep sutures. The large, thin, horny operculum lacks calcareous carbonate and is usually not preserved in fossilized specimens. In most species, the shells are thin, often stabilized by spiral ribs or bands, and relatively large, ranging between 25 and 70 mm in height. Based on their near-global distribution and abundance, the Viviparidae are thought to have evolved before the break-up of the Pangaea supercontinent, and thus at least during the Jurassic (Wenz 1938-1944; Hamilton-Bruce et al. 2002; Strong et al. 2008). The highest diversity of extant Viviparidae is found in East