Pentamerus oblongus Sowerby in Murchison, 1839 - fossil brachiopod from the Silurian of Ohio, USA.
<p>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).
</p><p>This large pentamerid brachiopod is an internal mold in dolostone - the original shell has dissolved away, leaving an impression of the shell's interior surface.
</p><p>Classification: Animalia, Brachiopoda, Articulata (also known as Rhynchonelliformea), Pentamerida, Pentameridae
</p><p>Stratigraphy: apparently derived from the Guelph Dolomite (= upper Lockport Dolomite), upper Niagaran Series, (~middle to upper Wenlockian), upper Middle Silurian
</p>
Locality: Lime City Quarry, northeastern side of Lime City, Perrysburg Township, northern Wood County, northwestern Ohio, USA (41° 32' 13" North latitude, 83° 33’ 45" West longitude)
James St. John
CC BY 2.0
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