File:Ectenocrinus simplex (fossil crinoids) (Kope Formation, Upper Ordovician; Cincinnati area, USA).jpg

English: Ectenocrinus simplex (Hall, 1847) - fossil crinoids in limestone from the Ordovician of the Cincinnati area, USA.

The famous Cincinnatian Series of the tristate area of Ohio-Kentucky-Indiana has some of the richest fossiliferous rocks on Earth. Cincinnatian rocks were deposited in relatively shallow marine facies during the Late Ordovician. The Cincinnatian succession is mostly interbedded limestones and shales. Most of the limestones are event beds (= tempestites), deposited during ancient storms.

The Cincinnatian fossiliferous limestone shown above has a "logjam" of Ectenocrinus crinoid stems, plus some articulated crowns. Crinoids (sea lilies) are sessile, benthic, filter-feeding, stalked echinoderms that are relatively common in the marine fossil record. Crinoids are also a living group, but are relatively uncommon in modern oceans. A crinoid is essentially a starfish-on-a-stick. The stick, or stem, is composed of numerous stacked columnals, like small poker chips. Stems and individual columnals are the most commonly encountered crinoid fossils in the field. Intact, fossilized crinoid heads (crowns, calices, cups) are unusual. Why? Upon death, the crinoid body starts disintegrating very rapidly. The soft tissues holding the skeletal pieces together decay and the skeleton falls apart.

Classification: Animalia, Echinodermata, Crinoidea, Disparida, Homocrinidaee

Stratigraphy: Kope Formation, Edenian Stage, lower Cincinnatian Series, Upper Ordovician

Locality: unrecorded/undisclosed site in the Cincinnati area (= tristate area of southwestern Ohio-southeastern Indiana-northern Kentucky), USA