Biodiversity of Mississippian (Lower Carboniferous) crinoids from Bradford Dale, Derbyshire, UK

Abstract

Crinoid diversity and abundance was higher during the Early Carboniferous (Mississippian) than at any other time. Due to the systematic focus on more complete specimens of crinoids, some areas, like the White Peak of Derbyshire and Staffordshire, UK, have erroneously been considered poor in fossil crinoids. Indeed, cups and crowns have only rarely been found in this area, but many limestones and cherts from the White Peak are rich in disarticulated crinoid remains. Screwstones (=fossiliferous cherts) collected in Bradford Dale, Derbyshire, yielded the disarticulated stem fragments, preserved as natural moulds, of seven crinoid morphotaxa, which is more than half of the known species richness of the whole White Peak. Considering that the material studied herein came from one locality, it is thus probable that the diversity of Mississippian crinoids in the White Peak is somewhat higher than previously recognized. This study shows that disarticulated stem fragments can be used as a proxy to test the crinoid diversity of an area, and that with further study of not only cups and crowns, some areas preserve a diversity of crinoids that is more than previously known.