RARE SMALL RADSTOCKICERAS AMMONITE - Southwest Germany

JURASSIC PERIOD (LIAS - PLIENSBACHIAN SUBSTAGE):  191 - 184 million years ago

From the Pliensbachian substage of a Jurassic deposit in southwest Germany, this rare type ammonite is of the genus Radstockiceras, a memeber of the Oxynoticeratidae family.  It possesses an oxycone and highly involute shell.  The outer ornamentation in this category is lacking with the surface being virtually entirely smooth.  The body is very laterally compressed with a sharp keel.  While most ammonites lived on or near the ocean bottom, it is likely that based on the low drag shell design of this ammonite, it swam in the open sea.  The beautifully graceful shape of Radstockiceras would have been perfectly suited for speed and allowing it to be able to swim against strong ocean currents with ease.

This particular specimen is mostly complete with a very shallow flake of the outer surface missing having stuck to the matrix when it was collected.  Still, a fantastic example of a type that is rarely if ever seen for sale and usually missing in most collections.  Natural pigment and excellent suture detail make this a fascinating little display specimen.  Entire ammonite is UNBROKEN AND HAS NO REPAIR AND NO RESTORATION. 

Ammonites are extinct members of the Cephalopod class.  Modern members include nautilus, squid and octopus.  They first appeared during the Silurian Period (435 million to 410 million years ago) and were abundant and widespread in the seas of the Jurassic and Cretaceous periods (175 million to 65 million years ago).  Ammonites are important index fossils—that is, they often link the rock layer in which they are found to specific geological time periods.

Ammonites varied greatly in size.  The largest known as small as 2 cm (0.75 in) in diameter.  During the Jurassic and Cretaceous periods, ammonites evolved more streamlined shells for swimming and the structure of the shell became stronger.  Different shell shapes emerged as well, such as snail-like or uncoiled.   

The shells of ammonites had hollow chambers separated by walls called septa.  A tube called the siphuncle, connected the body with the chambers allowing the animal to fill them with water or air, changing its buoyancy in order to rise or drop in the ocean.  Only the last and largest chamber was occupied by the living animal.  

Ammonites probably lived for one to six years, with the majority living two to four years.  They fed on plankton (tiny free-floating organisms), sea lilies, and smaller orthoceras.  Although many fed off the ocean floor, others may have caught plankton while floating or swimming via jet propulsion, expelling water through a funnel-like opening to propel themselves in the opposite direction.

Because ammonites lived exclusively in marine environments, their presence also indicates the location of prehistoric seas.

AFFORDABLE YET VERY UNCOMMON TYPE - RARELY SEEN IN COLLECTIONS!

2" wide

$90     AMX-045     INCLUDES STAND     Actual Item - One Only

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