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Invertebrate Fossils of NJ

Exogyra sp. (Say)

   The oysters Exogyra and Pycnodonte were the most common bivalves of the Cretaceous period. Lying on the seabed floor with the convex side in the mud and the flat side position at the seafloor surface for camouflage. Exogyra first appeared in the lower Cretaceous and had disappeared by the upper Cretaceous. These fossil remains can be found in abundance at numerous locations in Monmouth County.

Five species of Exogyra that have been reported from New Jersey;

Exogyra cancellata (Stephenson)
Exogyra costata (Say)
Exogyra erraticostata (Stephenson)
Exogyra spinifera (Stephenson)
Exogyra ponderosa (Roemer)

Oysters are often found riddled with bore holes. This is from the boring sponge
Cliona cretacica.


 

Exogyra costata from Monmouth County, NJ

 


 

Characteristic spiral coil of Exogyra.
 


 

Exogyra sp. with both valves.
 


 

The example of Exogyra spinifera measures over 5 inches across.
This shell is over 1 inch thick in places.
Monmouth County, NJ.

 


 

Upper valve from an unknown species.
 


 


These things can get rather large, but tend to lose their distinguishing markings
as the size increases.

 


 


Many of our local streams that cut through the Cretaceous marls will expose
large sections of oyster beds. This block, weighting several hundred pounds
was carved out of a very large exposure and now resides in the MAPS
collection. (Ralph Johnson - curator)
(Click to enlarge)
Note: This was taken from private property with the owners permission.

 

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