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JURASSIC SEA LIFE FOSSIL CLAMS AND AMMONITES IN MATRIX

Gottingen, Germany

EARLY JURASSIC PERIOD (LIAS):  200 - 176 million years ago

From an Early Jurassic deposit in Germany, this unusual fossil rock contains multiple remains of clams and ammonites - preserved sea life from a classic period of prehistory.  The ammonites and clams have been wonderfully preserved in full three dimensional form One of the primary clams is actually removable from the matrix and both sides are beautifully fossilized with intact luster from the original shell.  The outer ornamentation of the ammonites  can be seen in one repaired partial example as well as embedded associated examples.  This is the only specimen of this material we collected years ago.  Perfect for any sea life exhibit from the past. 


Bivalves, which include clams and mussels, are made up of two half shells.  The valves are attached by a hinge ligament and articulate open and close by two muscles attached on the inside of the shells.  Bivalves are filter-feeders and pump water inside their bodies to strain out phytoplankton and other small organisms for food.  Bivalves generally have limited locomotion and possess a foot but mainly live attached to some type of substrate or burrow in the underwater sand.  Bivalves move along the bottom by means of jumping.  The foot is extended then contracted violently, moving backwards in the process acting like a spring always kicking the animal slightly forward.

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.

UNCOMMON TYPE OF FOSSIL SEA LIFE FROM THE JURASSIC - PERFECTLY PRESERVED 3D CLAM IS REMOVABLE AS SEEN ABOVE

4.5" in length overall

SOLD     BIV-011     Actual Item - One Only

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