Paleoecological Significance of a Pre-Mortem Crinoid-Coral Interaction from the Silurian of Southeastern Indiana

A noteworthy specimen recording a syn vivo interaction between stalked echinoderm and tabulate coral is described herein from the middle Silurian (Wenlock: Sheinwoodian) Massie Formation of Ripley County, southeastern Indiana. Part column camerate crinoid Eucalyptocrinites encrusted around entirety its lateral margin by favositid colony. The radially outward orientation corallites on both upper lower surfaces colony show that was elevated completely above seafloor and, more importantly, had to be vertical at time initial encrustation subsequent astogeny. Hence, host most likely alive throughout duration this interaction. No evidence for paleopathological reaction present column, suggesting encruster did not adversely affect host. This reflects long inflexible Eucalyptocrinites, which could have supported encrusting, secondarily tiered organisms—even relatively heavy ones—without interfering with biological functions crown or weighing down column.