English: Antiquatonia coloradoensis (Girty, 1910) - productid brachiopod (view of dorsal valve) from the Pennsylvanian of Ohio, USA.

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).

The Antiquatonia brachiopod shown above is from the Boggs Shale, a marine fossiliferous mudshale unit that caps the Boggs Limestone in the Pennsylvanian-aged Pottsville Group of eastern Ohio, USA. Fossils are moderately common in this unit at this locality (Blunt Run, Muskingum County) and include brachiopods (Anthracospirifer occiduus, Antiquatonia coloradoensis, Composita cf. Composita subtilita, Rugosochonetes delicatus), encrusting bryozoans, fenestrate bryozoans, carbonized wood, bivalves, and crinoid stems.

Classification: Animalia, Brachiopoda, Articulata (a.k.a. Rhynchonelliformea), Strophomenida, Productidae

Stratigraphy: Boggs Shale (just above the Boggs Limestone), middle Pottsville Group, lower Atokan Stage, lower Middle Pennsylvanian

Locality: loose talus block along Blunt Run (= east-flowing tributary of the Muskingum River), Muskingum Township, north-central Muskingum County, eastern Ohio, USA (~40° 01' 44.88" North latitude, ~81° 59' 49.48" West longitude)