Crinoid fossils known as Pentacrinites have been found attached to wood by long stems in small colonies. More recent crinoids related to Pentacrinites live on rocks and are attached with a shorter stem. The vast majority of modern crinoids have evolved to be stem-less and can swim around freely. Some of the free-swimming ancestors of these crinoids are the Marsupitsa, Saccocoma and Uintacrinus crinoid fossils. These free-swimming crinoid fossils have been discovered in the Niobrara chalk of Kansas and the Solnhofen limestone of Solnhofen Germany. The Niobrara chalk of Kansas has many free-swimming Uintacrinus crinoid fossils dated back to the Cretaceous. The Solnhofen limestone in Solnhofen Germany has many Pterocoma crinoid fossils dated back to the Jurassic. |
