Crinoids
Sea lilies — crinoids have perched on the ocean floor for 480 million years, their graceful arms filtering food from the current.
Overview
Crinoids — sea lilies — are echinoderms that anchor to the seafloor and sweep food from the water with graceful, feathery arms. They built 'gardens' across Palaeozoic sea floors, and though reduced today, over 600 living species still persist in modern oceans.
Quick Facts
Key Characteristics
- •Stem (or holdfast) topped by a cup-shaped calyx bearing the arms
- •Five arms (commonly branching) lined with food-gathering pinnules
- •Pentaradial symmetry throughout the adult body
- •Skeleton of discrete calcite plates — columnals, calyx plates, arm plates
Fossil Record
Disarticulated columnals are among the most common Palaeozoic fossils; complete calyces with arms are rarer prizes. Mississippian limestones of North America and Europe are famously crinoid-rich; Crawfordsville, Indiana preserves complete stemmed crinoids in soft shale.
Global Distribution
Global in marine rocks — especially abundant in Mississippian beds of the American Midwest and England.
Evolutionary & Scientific Importance
Crinoids dominated Palaeozoic seafloor communities, are key index fossils for the Mississippian, and their plate-by-plate skeletons record echinoderm development and the survival of a lineage across the end-Permian bottleneck.