Cincinnatian Fossils from the Ordovician

Cincinnatian Fossils

From The Ordovician Period

A Guide to the Ordovician Fossils of Southeast Indiana Collected by Jeff Bryant


Arthropoda Cnidaria
Arthropoda Cnidaria Brachiopoda Molluska Echinodermata Bryozoa Hemichordata

Ordovician Mollusk Fossils

An important characteristic of most molluscs is the head-foot region. Most molluscs are strongly cephalized; that is, they have a well-developed head, in which is located a mouth and a concentration of nervous and sensory functions. Adjacent to the head is a large, muscular foot formed from the ventral body wall. Used primarily in locomotion, the surface of the foot is sometimes ciliated and laden with numerous mucous glands. Another characteristic of most molluscs is the mantle. This sheath of tissue is formed from the dorsal body wall. It surrounds the mantle cavity, which houses the gills or lungs if they are present, and its surface may assist in gas exchange. The mantle also secretes the shell in those forms that possess one. Mollusks have a complete digestive tract, spanning from the mouth to the anus. Many also have a radula, a unique organ composed mostly of chitin, in the mouth. The radula allows the animal to scrape food from surfaces, especially the ocean floor, by sliding back and forth.

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Genus/species: Tentaculites richmondensis
Images Tentaculites richmondensis
Notes: Well preserved specimen 1.79 cm in length. Tentaculites is a bizarre creature and it's true classification is unknown, but many people place it in the phylum molluska.

Genus/species: ?Richmondoceras sp.
Images ?Richmondoceras sp. ?Richmondoceras sp.
Notes: First specimen is a mold of an orthocerid . Approx. 2 cm in length.
Second specimen is another mold of an orthocerid 2.33 cm in length.

Genus/species: ?Treptoceras sp.
Images ?Treptoceras sp.
Notes: Another mold of an orthocerid 3.51 cm in length.

Genus/species: ?Lambyoceras sp.
Images ?Lambyoceras sp.
Notes: A mold of an orthocerid 3.13 cm in length. This specimen differs from the above by the fact that the chambers are narrower and more curved

Genus/species: unknown nautiloid
Images unknown nautiloid unknown nautiloid
Notes: Unknown nautiloid 5.6 cm in length and 2.75 cm wide. Chamber segments are about 0.4 cm wide. Still heavily encased in matrix.

Genus/species: Platyostoma niagarense (Silurian)
Images Platyostoma niagerense Platyostoma niagerense Platyostoma niagerense Platyostoma niagerense

Extremely well preserved gastropod specimen. Approx. 2.8 cm wide. Specimen provided by Vern Swanson of Alexandria, IN.

Genus/species: Cyclonema sp.
Images Cyclonema sp. Cyclonema sp.
Notes: Well preserved specimen 1.09 cm high and 1.42 cm wide.


Genus/species: ?
Images ?Cyclonema sp.
Notes: This specimen is difficult to classify, but the angle of the shell growth and spiral shape may indicate that this is a fragment of a Cyclonema specimen. This specimen has a slightly flatter profile than usual for Cyclonema so this classification may be in error. No exact match is found in the reference. The specimen is .85 cm high and approximately .78 cm wide.

Genus/species: ?Augustoceras sp.
Images ?Augustoceras sp.
Notes: Internal mold of a specimen. Augustoceras is not listed in the reference so this classification may be in error. Specimen is 1.32 cm at its widest point and .43 cm high.

Genus/species: Ambonychia sp.
Images Ambonychia sp.
Notes: Pelycopod specimen 4.19 cm in length and 2.64 cm wide.

Genus/species: Unknown pelycopod
Images unknown pelycopod unknown pelycopod
Notes: Unknown pelycopod specimen 3 cm in length and 2 cm wide. The color is noticeably black.