Sea Lilies in Spring: Crinoid Diversification During the Early Ordovician

The many Early Ordovician crinoid discoveries over the past 30 years signal a largely undocumented crinoid radiation. The new crinoid diversity totals more than five times the previous known Early Ordovician list as of the year 2000. Camerate, cladid, and disparid clades had emerged by the second half of the Tremadocian Series, early during this time. Many key crinoid features such as their distinctive arms and standard cup plating originated by the end of the Early Ordovician, the Floian Stage. These new finds will provide data for character analysis in phylogenetic reconstructions, particularly those aimed at identifying early branching within the crinoid tree. Early Ordovician crinoids were 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.