Group F Mesodons - (Family Polygyridae)
There are four species in this group. The first two are part of Group F1 - large, globose, closed umbilicus and parietal tooth. Mesodon elevatus is more globose when you look at the shell from the side - a higher rounder spire compared to Mesodon zaletus.
The third and fourth species are part of the F2 - large, globose-or-so, closed umbilicus, toothless snails - Mesodon mitchellaneus and Mesodon normalis - both of which are very similar to Neohelix albilabris and Patera pennsylvanica.
Mesodon elevatus (Say, 1821)
Mesodon elevatus (Say, 1821)
Common Name: Proud Globe Snail
Characters: Heliciform, reflected lip, globose, imperforate, ~18-26 mm; noticeable high spire, large parietal tooth, basal lip straight with small ridge.
Comparison: The high spire in this globose shell separates the Proud Globe from other Mesodon species.
Habitat: This is a forest species that may be found in heavily wooded ravines or woodlands along river corridors and in drier upland woodlands.
Status: Found throughout the state in suitable habitat.
Mesodon zaletus (A. Binney, 1837)
Mesodon zaletus (A. Binney, 1837)
Common name: Toothed Globe Snail
Characters: Heliciform, reflected lip, globose to subglobose, imperforate, ~19-31 mm; small parietal tooth (may be absent), sturdy shell.
Comparison: Shells may be confused with Mesodon thyroidus, but M. thyroidus is rimate, not imperforate and has a thinner shell. The Elevated Globe tends to more globose (and rounded), compared to the Toothed Globe.
Habitat: This is a forest species found in mesic and xeric woodlands, mesic wooded slopes with mature forest cover and can be found in moist leaf litter and talus along river corridors.
Status: Common throughout the state in suitable habitat.
see image of Mesodon mitchellianus
Mesodon mitchellianus (I. Lea, 1839)
Common Name: Sealed Globelet Snail
Characters: Heliciform, reflected lip, globose to subglobose, rimate, ~15-19 mm, no parietal tooth.
The Sealed 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.
Status: Uncommon and scattered distribution in central and southern Indiana
see image of Mesodon normalis
Mesodon normalis (Pilsbry, 1900)
Common Name: Grand Globe Snail
Characters: Heliciform, lip reflected, shell with 5.5-6 whorls, imperforate, no teeth, 21-34 mm diameter
Comparison: The most similar species are the other globose toothless F2s: Mesodon mitchellianus, Neohelix albolabris, or Patera pennsylvanica.
Habitat: found in ravines and on mountainsides and upland habitats, likes acidic soils, mixed hard-woods but also reported to be found in pine woods around logs.
Status: Rare in the state, overall status not known. Three vintage collections with last one in 1948.
