Faunas of disarticulated ossicles, particularly columnals, are a potentially important source of data for helping to elucidate the patterns of evolution and extinction shown by pelmatozoans in the late Ordovician. The columnal fauna of the Hirnantian High Mains Formation, Craighead Inlier, Strathclyde, includes the following morphotaxa: Cyclocyclicus (col.) foraminosus sp. nov.; Cyclocyclicus (col.) periogmos sp. nov.; Hypsinomocrinus (col.) lewisi gen. et sp. nov.; Tetragonotetragonalis (col.) girvanensis sp. nov.; and Pentagonopentagonalis (col.) sp. This is the first Hirnantian columnal fauna to be described from the North American province; it is distinctly different from Hirnantian columnal biota described from Wales and Kazakhstan.
