The many Early Ordovician crinoid discoveries over the past 30 years signal a largely undocumented crinoid radiation totalling a more than five-fold increase in diversity, an important event in crinoid history. Camerate, cladid, and disparid clades had emerged by the Late Tremadocian Series, early during this time. These finds provide data for character analysis in phylogenetic reconstructions, particularly those aimed at identifying early branching within the crinoid tree. Early Ordovician crinoids comprised among the earliest-known benthic invertebrates to exploit food resources high above the substrate. Significantly, they were also among the largest known faunal elements during this time. A tentative listing of Early Ordovician crinoids and their distributions is provided; this compendium is subdivided into time slices with Laurentian and global stratigraphic units.