File:Brachiopods in limestone (Waynesville Formation, Upper Ordovician; Roaring Run, Warren County, Ohio, USA) 1.jpg

English: Brachiopod fossils in limestone in the Ordovician of Ohio, USA. (bedding plane view)

This fossil plate is from the famous Cincinnatian Series of the tristate area of Ohio-Kentucky-Indiana. Rocks in the Cincinnatian 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 fossiliferous limestone shown above is eroded from an outcrop of the Waynesville Formation, a richly fossiliferous marine unit in the upper Cincinnatian Series. Overall, the Waynesville is about 30% limestone and 70% shale - it was deposited in a shallow carbonate platform setting, but well below fair weather wave base.

The prominent fossils are complete and fragmentary brachiopod shells (readily identifiable forms include Rafinesquina ponderosa, Leptaena richmondensis, and Platystrophia sp.). Brachiopods are sessile, benthic, filter-feeding, marine invertebrates. They first appear in Cambrian rocks and were abundant in Earth's oceans throughout the Paleozoic. They were also common in Mesozoic oceans, but are scarce in modern oceanic biotas. Brachiopods have two shells, called valves, that are usually calcareous (made of calcite - CaCO3 - calcium carbonate). Each shell of a brachiopod is bilaterally symmetrical, unlike each shell of a bivalve (clam).

Classification: Animalia, Brachiopoda, Articulata (also known as Rhynchonelliformea)

Stratigraphy: Waynesville Formation, Richmondian Stage, upper Cincinnatian Series, upper Upper Ordovician

Locality: Roaring Run, Caesar Creek Lake State Park, northeastern Warren County, southwestern Ohio, USA (vicinity of 39° 28' 41.63" North latitude, 84° 03' 46.83" West longitude)