Fossil crinoids from Panthalassa

Today, stalked crinoids are confined to the deep sea, although their ancestors once dominated shallow-marine environments. Our analysis of the fossil record from the ancient Panthalassa Ocean shows that their restriction to deep-water habitats occurred much later than in the Tethyan realm. These findings indicate that marine ecosystem restructuring proceeded at different rates across the globe, challenging the idea of a globally synchronous impact of the so-called Mesozoic Marine Revolution.

Figure: Crown of an Oligocene crinoid from Oregon.