Fasciculiconcha knightii Newell, 1937 - fossil bivalve in fossiliferous limestone in the Pennsylvanian of Ohio, USA.

This rock is from the Upper Mercer Limestone in the Pottsville Group, a Pennsylvanian-aged cyclothemic succession containing nonmarine shales, marine shales, siltstones, sandstones, coals, marine limestones, and chert ("flint"). The lower Pottsville dates to the late Early Pennsylvanian. The upper part dates to the early Middle Pennsylvanian. The Lower-Middle Pennsylvanian boundary is apparently somewhere near the Boggs Member (?).

The Upper Mercer Limestone is a moderately laterally persistent, chertified limestone horizon in the Pottsville Group. It is often composed of black-colored chert/flint but can be dark bluish to bluish-black colored as well (the latter colors are referred to as "Nellie Blue Flint"). Upper Mercer Flint has light-colored fossils and fossil fragments that include fusulinid foraminifera, crinoid ossicles, and other Late Paleozoic normal marine fossils. Apparent phylloidal algae can also be present as squiggly lines.

Non-chertified limestone is frequently present in the Upper Mercer horizon, although minor in volume. Limestone usually occurs along the outside portions of chert masses, but also in relatively small patches within the chert.

In places, the Upper Mercer Flint/Limestone horizon is missing, usually removed by paleoerosion.

American Indians sometimes used Upper Mercer Flint to make arrowheads and spear points and knife blades. "Flint Ridge Flint" (= Vanport Flint) was the most desirable source rock for these objects, but other chert horizons also attracted attention.

This fossil bivalve is in the limestone lithology of the Upper Mercer. Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates.

Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood.

The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record.

The nice, decent-sized fossil scallop shown above is Fasciculiconcha knightii, which has been previously reported from marine limestones in the Pottsville and Allegheny Groups (Lower to Middle Pennsylvanian) of Ohio (see Hoare et al, 1979).

Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Pterioida, Pectinidae or Aviculopectinidae

Stratigraphy: Upper Mercer Limestone, upper Pottsville Group, Atokan Stage, lower Middle Pennsylvanian

Locality: Rock Cut railroad cut - loose talus piece derived from outcrop along the southern side of Ohio Central Railroad tracks (west of milepost 134), ~southwest of Copeland Island & south-southeast of the town of Dresden, northern Muskingum County, eastern Ohio, USA (~vicinity of 40° 04’ 24.41” North latitude, ~81° 59’ 11.25” West longitude)

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