Fossil Sea Lilies — Jurassic Display

This fossil mural features two large crinoids, a type of marine invertebrate colloquially known as a "sea lily." These sea lilies lived 180 million years ago in the prehistoric Tethys Ocean that covered much of present-day Europe and Asia. Spending almost their entire lives attached to the piece of driftwood seen here, they flourished in a rich underwater world alongside other marine animals including fish, ammonites, and belemnites. As sessile filter feeders, crinoids relied on the movement of the driftwood or floating debris to which they were attached to venture into areas with adequate food supply. Crinoids were nevertheless able to bend their stalks and flex and extend their arms — the central appendages in their crowns — so that their mouths could face the water current to capture potential food.

Crinoids bred once a year when their eggs or sperm were released into the water. Once the eggs were released from the parent and fertilized, the resulting embryo would attach itself to a solid substrate such as driftwood where it would develop for several days into a barrel-shaped, free swimming larva. After several more days, the larva would reattach to the driftwood and develop a rudimentary stem, mouth, and five small arm-like tentacles known as podia. After several more weeks, the crinoid would reach the stalked, sessile stage, where it formed true arms, feather-like pinnules, and a complete set of podia that covered the pinnules and helped move food toward the mouth. After about a year of life, the crinoid would become fertile and produce either eggs or sperm, thus continuing the propagation of the species.

Eventually, these sea lilies succumbed to death and became buried on the sea floor, where the low-oxygen environment allowed for their pristine preservation and fossilization. Over millions of years, the sediment and animal remains surrounding these two animals petrified and became the dark grey Posidonia shale seen here, now famously extracted from the quarries of Holzmaden, Germany.