Hyolitha from the Early Paleozoic glacial erratic boulders (Geschiebe) of Germany and Poland

Hyoliths from glacial erratic boulders, or Geschiebe, from northern Germany and Poland include representatives of Hyolithes acutus Eichwald, 1840, the type of the genus. Geschiebe individuals of that taxon reinforce and augment the revised generic concept of Hyolithes of Malinky (2006), and extend the range of morphologic variation in terms of longitudinal sculptural elements and apical curvature. Occurrences in the Geschiebe of Crispatella Malinky, 2002 and Dorsolinevitus Syssoiev, 1958, reinforce the notion of distinct hyolith paleobiogeographic provinces in the Ordovician, with these forms belonging to the Baltic province of Marek (1976). Operculum A is the first operculum identified to possess an epibiont on the exterior. Hyolithes esthonus Koken, 1889 is herein transferred to Dorsolinevitus with question, and several other specimens are assigned to that genus but left in open nomenclature at the species level. Nevadotheca ? sp. and Holmitheca ? sp. are both recognized from Early Cambrian erratic sandstone boulders, suggesting that these forms lived in shallower, more nearshore environments than their occurrences elsewhere would suggest. “Hyolithes ” vaginati (Quenstedt, 1852), the first hyolith species recognized from a boulder, is deemed unrecognizable due to inadequate preservation. The supposed Silurian hyolith Ceratotheca erratica (Koken, 1889) is herein transferred to the Gastropoda