Rimate Mesodons - Mesodon thyroidus and Mesodon clausus (Family Polygyridae)Â
These two species are typical Mesodon snails with the more-or-less globose shell. What distinguishes them from other Mesodons is the rimate umbilicus and what distinguished them from each other is the parietal tooth and size. The species are Mesodon thyroidus, the White-lip Globe and Mesodon clausus, the Yellow Globelet.
Mesodon thyroidus (Say, 1816)
Mesodon thyroidus (Say, 1816)
Common Name: White-lip Globe
Identification: subglobose shell, with a small parietal tooth that can be missing, peristome partially covers the umbilicus (rimate), adults usually 17-22 mm. Shells without a parietal tooth may be confused with Mesodon clausus, but can be distinguished by the smaller size of the Yellow Globelet and its rounder profile.
Habitat: found in woodland habitats associated with decaying woody debris, small rock piles, walls, or ledges; also commonly associated with urban residential landscapes; one of the two commonest species listed on iNaturalist from Indiana. The other is the Eastern Whitelip (Neohelix albolabris) with which it is often confused with images only showing the top of the shell.
Mesodon clausus (Say, 1821)
Mesodon clausus (Say, 1821)
Common Name: Yellow Globelet
Identification: Heliciform, reflected lip, globose to subglobose, rimate, ~15-19 mm, no parietal tooth.
The Yellow Globelet may be confused with smaller shells of the larger species Mesodon thyroidus that lack a tooth. It tends to be more globose. The rimate umbilicus separates it from other Mesodons.
Habitat: Mesodon is a woodland snail, has been found recently in woodland areas associated with rotting branches and fallen timber. Scattered in the state, may be under-collected.
