File:Flexicalymene meeki (fossil trilobite) (Cincinnatian Series, Upper Ordovician; Cincinnati area, USA) 1.jpg

English: Flexicalymene meeki (Foerste, 1910) - enrolled fossil trilobite from the Ordovician of the Cincinnati area, USA. (~2.7 centimeters across at its widest)

Trilobites are extinct marine arthropods. They first appear in Lower Cambrian rocks and the entire group went extinct at the end of the Permian. Trilobites had a calcitic exoskeleton and nonmineralizing parts underneath (legs, gills, gut, etc.). The calcite skeleton is most commonly preserved in the fossil record, although soft-part preservation is known in some trilobites (Ex: Burgess Shale and Hunsruck Slate). Trilobites had a head (cephalon), a body of many segments (thorax), and a tail (pygidium). Molts and carcasses usually fell apart quickly - most trilobite fossils are isolated parts of the head (cranidium and free cheeks), individual thoracic segments, or isolated pygidia. The name "trilobite" was introduced in 1771 by Johann Ernst Immanuel Walch and refers to the tripartite division of the trilobite body - it has a central axial lobe that runs longitudinally from the head to the tail, plus two side lobes (pleural lobes).

This specimen is enrolled - many trilobites could roll up like modern terrestrial isopods (see: villenatura.blogspot.com/2011/04/armadillium-opacum.html). This was usually in response to being buried in sediments - often by storm events.

Classification: Animalia, Arthropoda, Trilobita, Polymerida, Calymenidae

Stratigraphy: unrecorded unit in the Cincinnatian Series, upper Upper Ordovician

Locality: unrecorded/undisclosed site in the Cincinnatian outcrop belt of southwestern Ohio-southeastern Indiana-northern Kentucky, USA