Xolotrema - Wedge Snails (Family Polygyridae)
Three species of Xolotrema are possible: the Bladetooth Wedge Snail (Xolotrema fosteri), the Velvet Wedge Snail (Xolotrema denotatum), and the Sharp Wedge Snail (Xolotrema obstrictum). Dourson (2010) has a very good treatment of Xolotrema.
This key is based on Dourson (2010) on characters for KY specimens.
1a. palatal tooth significant and deeply recessed, shell surface with hairs – Xolotrema dentifera
1b. palatal tooth more marginal and smaller (might be poorly defined), no hairs – go to 2
2a. periphery and shoulder more rounded – Xolotrema fosteri
2b. periphery and shoulder carinate or strongly angular - Xolotrema obstrictum
Xolotrema fosteri (F. C. Baker, 1921)
Xolotrema fosteri (F. C. Baker, 1921)
Common name: Bladetooth Wedge
Identification: shell imperforate, large parietal tooth, subglobose, rounded periphery, shell usually >17 mm, tooth in upper part of outer lip. This may be confused with some Patera species if the palatal tooth is particularly small and not noticeable - or absent.
Habitat: woodland species, associated with woody debris, limestone hillsides and outcrops, large boulders.
Status: Second most commonly found species of this genus.
Below are three images of newly hatched Xolotrema fosteri. Two adults wandered into my yard in early May. I kept them and the magic happened - about 2 dozen eggs (deposited end of May) turned into the same number of neonates. These are no older than 11 days. The eggs were about 2 mm diameter. Note the open umbilicus and lack of reflected lip.
Xolotrema denotatum (Férussac, 1821)
Xolotrema denotatum (Férussac, 1821)
Common name: Velvet Wedge Snail
Identification: shell imperforate, large curved parietal tooth, subglobose, notable basal tooth, palatal also significant and deeply recessed; shell usually >17-26 mm. This might be confused with a Threetooth snail, but this umbilicus is closed, not open as in Triodopsis. Hotopp et al. (2020) note this species has the shell is with "fine, hair-like processes, giving it a moleskin-like texture" and that older "shells lose this fine coating as it is part of the outer protein coat, or periostracum".
Habitat: woodland species, associated with large woody debris, hillsides and outcrops, large boulders. mesic, and according to Oesch et al. 2013 and Hubricht 1985 - on associated floodplains.
Status: The most commonly identified Xolotrema, widespread in the state .
Xolotrema obstrictum (Say, 1821)
Common name: Sharp Wedge Snail
Identification: shell imperforate, large parietal tooth, basal tooth small and could be minimal, palatal tooth significant; shell 17-27 mm, not hairy, periphery carinate to strongly angular.
Habitat: according to Dourson (2010) this species prefers limestone bluffs and outcrops with live snails being found pressed into recessions and crawling around the rock at night.
Status: The most least identified Xolotrema, widespread in the state.
