Order: Ammonitida (Hyatt 1889)

Ammonites are an extinct group of marine animals known worldwide for their chambered spiral shell. This shell contained a series of progressively larger chambers, these chambers are divided by thin walls called septa. The last and largest chamber, the body chamber, was occupied by the living animal, as it grew, it added newer and larger chambers to the open end of the coil. A tube passed through the septa, extending from the ammonite's body into the empty shell chambers enabling the ammonite to control it's buoyancy by filling the empty chambers with air or water. The most common ammonite fossil in New Jersey are the isolated chambers, complete ammonites tend to be location specific and very fragile.  


Fossilized ammonite chamber.
This is the most common find in NJ


Placenticeras minor, measures 5 cm (2 inches)

Wenonah Formation - Cretaceous
Monmouth County, NJ




Sphenodiscus lobatus, measures 21 cm (8 inches)
 This is my only complete NJ ammonite, found in several pieces and glued back together.

Tinton Falls Formation - Cretaceous
Monmouth County, New Jersey



Placenticeras placenta with a bit of original shell.

The ammonite shell is composed of aragonite, an unstable form of calcium carbonate which usually has been dissolved
by the acidic ground water in New Jersey.
Woodbury Formation - Cretaceous
Camden County, NJ


Small fragment of original ammonite shell, This is a view is the inside with the septa attached to
the outside wall. 


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