R- and Q-mode cluster analysis of data on the occurrence and distribution of 43 conodont species enables delineation in North America of warm-water Red River and Ohio Valley provinces during the Late Ordovician Velicuspis Chron, and suggests recognition of six major biofacies that represent a continuum from nearshore, shallow-water biotopes with numerous endemics to offshore, deeper-water biotopes characterized by more cosmopolitan species. Approximately coeval conodonts from Great Britain, Baltoscandia, and continental Europe are assignable to at least 36 taxa, which are less well known than those of equivalent age in North America but represent cold-water faunas whose Late Ordovician distribution and frequency of occurrence may be used to characterize British, Baltoscandic, and Mediterranean provinces, within which we recognize only three distinct biofacies. Only a third of the taxa in the Late Ordovician cold-water region are also represented in warm-water areas, where they characterize relatively deeper-water biofacies or have a distribution that indicates they were eurythermal cosmopolites. Late Ordovician conodonts are treated as components of warm- and cold-water pelagic faunas, not because their distribution demands that interpretation, but because the pelagic model is simpler than a benthic or nektobenthic one and squares readily with available distributional data.