Family Thysanophoridae Pilsbry, 1926

This is a small family of Nearctic and Neotropical snails occurring Alaska south along the west coast to the southern USA, in the Caribbean region, and through Central America to Colombia (Pilsbry 1940; Schileyko 2006). There is only one genus, Microphysula, and two species in Canada.

Genus Microphysula Cockerell in Pilsbry, 1926

  • Microphysula Cockerell in Pilsbry 1926: 117; type species by original designation: M. ingersollii (Bland, 1875).

Two living species; western North America from Alaska to the southwestern US states (Pilsbry 1940). Both species occur in Canada. Two additional Tertiary fossil taxa from Wyoming were attributed to Microphysula by Russell (1931).

Etymology. Greek: micron, small + physa, bubble + the Latin diminutive ending -ula. Feminine.

Microphysula cookei (Pilsbry, 1922)
Microphysula ingersollii (Bland, 1875)

Key to Microphysula

  • a Slightly smaller: width to 4.4 mm (coastal and north-western BC) — M. cookei
  • b Slightly larger: width to 4.8 mm (south-western BC, north along Rockies) — M. ingersollii