The Geology of Delaware

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Clams, Snails, and Squid: Phylum Mollusca, Class Cephalopoda

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Phylum Mollusca
Class Cephalopoda
Cephalopods are a group of molluscs that include the pearly chambered Nautilus, squids, and the octopus. They can be divided into three categories: the Nautiloidea (chambered Nautilus), the Ammonoidea (the extinct ammonites), and the Dibranchiata (squids, the extinct belemnites, and octopuses).

Ammonite fossils occur in places in the Cretaceous of Delaware. An ammonite can be thought of as an octopus stuffed inside a straight, coiled, or spiral shell. They are uncommon finds at the C & D Canal, usually occuring as broken pieces; a complete one is a rare and exciting find. Most of the larger coiled ones are found in the Merchantville Formation. Sections of the straight-shelled Baculites are more common in the Mount Laurel Formation.

The belemnite species Belemnitella americana is the Delaware State Fossil. They are amber colored, bullet-shaped fossils that served as the internal skeleton in an extinct squid-like animal called a belemnoid. Belemnites are a common find on the Mount Laurel spoils pile because they probably traveled in large schools.

Reference(s): 

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Photo Gallery
1. Placenticeras placenta - specimen from the Merchantville Formation<br>2. Menabites (Delawarella) delawarensis - specimen from the Merchantville Formation<br>3. Oxybeloceras sp. - specimen from the Mount Laurel Formation<br>4, 5. Baculites ovatus - specimen from the Mount Laurel Formation<br>6. Belemnitella americana - specimen from the Mount Laurel Formation<br>
Belemnitella americana - occurs in the Mount Laurel Formation<br>Cretaceous Cephalopoda illustration from Page 16, DGS Special Publication No. 19, 1992.
1, 2. Belemnitella americana - specimen from the Mount Laurel Formation<br>Cretaceous Cephalopoda photograh from Plate V, DGS Report of Investigation No. 21, by T. E. Pickett, 1972.
5. Menabites (Delawarella) delawarensis - specimen from the Merchantville Formation<br>6. Baculites ovatus - specimen from the Mount Laurel Formation<br>Cretaceous Cephalopoda photograph from Plate V, DGS Report of Investigation No. 21, by T. E. Pickett, 1972.
Placenticeras placenta - occurs in the Merchantville Formation<br>Menabites delawarensis - occurs in the Merchantville Formation<br>Belemnitella americana - occurs in the Mount Laurel Formation<br>Oxybeloceras sp. - occurs in the Mount Laurel Formation<br>Baculites ovatus - occurs in the Mount Laurel Formation<br>