Carychium nannodes

Carychium nannodes G.H. Clapp, 1905
Pygmy Thorn

  • Carychium nannodes G. H. Clapp 1905: 91, pl. 3, figs 7–9.

Identification. Shell elongate. Spire tapering; sides straight or nearly so. Whorls ca 5. Protoconch smooth. Teleoconch nearly smooth and incremental striae very faint, with 23–25 spiral rows of exceedingly tiny punctae (seen under at least 20× magnification; Burch & Van Devender 1978). Aperture subovate, ca 1/3 of shell height, with a parietal fold, continuing internally around the columella, and a smaller columellar fold below. Palatal lip expanded but little thickened; seen from the side, prosocline, nearly straight, not strongly sigmoid. Belly of last whorl not projecting beyond the plane of aperture. Shell shining, translucent and colourless when fresh; dead shells become white and opaque. Shell to 1.3–1.5 mm high (higher than wide).

Carychium nannodes is the smallest of the Carychium species in Canada. It is recognized by its diminutive size (≤1.4 mm), smooth shell without any trace of striae, and thin, although recurved, palatal lip. The internal lamella is smoothly curved.

Habitat. Mesic upland forests, such as along the Niagara Escarpment; in leaf litter. A rare species, most Ontario records are from stream drift.

Global range. Southern Ontario and in the USA, western Maryland southwest along the Appalachians to central Alabama and from Virginia west to Kentucky, Indiana, and Michigan (Hubricht 1985).

Canadian range. Ontario only; restricted to areas along the north shore of Lake Ontario. First reported by Oughton (1948) from stream drift of the Green, Rouge, Don, and Humber rivers. On the Niagara Escarpment at Crawford Lake, Halton Regional Municipality (Nekola & Barthel 2002). A rare species (although perceived rarity may be due to its small size and confusion with other Carychium species). Oughton (1948) first recorded this species in Canada; Burch & Van Devender (1978) and Nekola & Barthel (2002) figured shells from Ontario.

Etymology. Greek, nanos, “a dwarf”.