Palaeoecology of Jurassic encrinites: reconstructing crinoid communities from the Western Interior Seaway of North America

Abstract

Jurassic crinoid communities in North America are poorly known. However, encrinites (rocks chiefly composed of crinoid debris) are surprisingly common in North America, and represent some of the best examples of post-Palaeozoic crinoid accumulations. These rocks are highly significant for understanding the ecology of early isocrinid crinoids, and provide an insight into the wider crinoid communities of North America. Within this reanalysis of Jurassic crinoids of the Western Interior Seaway, a number of non-endemic forms are reported, together with some highly specialized crinoids. Encrinites are varied, with distinct marine and lagoonal communities recognized. These ecological associations are comparable to those seen in the European Jurassic, with many of the classic European genera being present. This new data, and existing data from the Jurassic shallow seas of Europe, demonstrates that crinoid distribution patterns are largely facies influenced while geographical factors are of limited importance. Even within the same region, taxa in lower energy offshore facies contrast strongly with those found in more restricted facies. However, very similar crinoid communities characterize comparable facies in North America and Europe.