Article: Palaeoecology and history of the Calceocrinidae (Palaezoic Crinoidea)

The morphologically divergent and long-ranging Calceocrinidae (inadunate crinoids, middle Ordovician to early Permian) are reinterpreted to have been leeward, passive, suspension feeders. Calceocrinid success is measured relatively by species diversity and by the relationship of calceocrinid species diversity to total crinoid generic diversity. The major change in calceocrinid importance occurred immediately after the Silurian, and this decline is judged to have been the consequence of biotic interactions. Both increased predation pressure and competition from fenestrate bryozoans are offered as potential causes for the decline; of the two, competition for living sites and exclusion by habitat modification by fenestrates is favoured. Accordingly the Devonian calceocrinid decline is argued to be the result of partial ecologic replacement of calceocrinids by fenestrate bryozoans. This study provides an example illustrating the impact that ecologic processes may have in evolutionary time.