An ordovician fauna from Lough Shee, Partry Mountains, Co. Mayo, Ireland

An hitherto undocumented early Ordovician fauna from mudrocks at Lough Shee in the Partry Mountains contains species of sponge, machaeridian, bivalve, gastropod, cephalopod, brachiopod, and trilobite, together consistent with a deep‐water setting marginal to the North American province. The trilobite and brachiopod data suggest a correlation of the Lough Shee mudrocks with the upper Whiterock Stage (equivalent to a level near the D. ‘bifidus’ – D. murchisoni boundary, within the middle Llanvirn). The sparse, low‐diversity assemblage is specialized and demonstrates the development of aspects of the Whiterock fauna in the South Mayo Trough.