Another united kingdom species, Similodonta magna was described in 1946 by Lamont and is known from Ashgillian fossils found near the Scottish coastal town of Girvan.
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The type species for the genus, Similodonta similis, has been found in Late Ordovician, Ashgill epoch, sediments of the upper Richmond Group exposed near Spring Valley, Minnesota.
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Similodonta spjeldnaesi is a late Ordovician species found in and described from the Upper Chasmops Shale, Ringerike, Norway.