LARGE DINOSAUR-ERA EOPACHYDISCUS AMMONITE - Duck Creek Formation - Cooke County, Texas, USA

CRETACEOUS PERIOD (EARLY UPPER ALBIAN STAGE) :  101 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.  This is especially true of this exquisite and very large example of the Cretaceous species of ammonite called Eopachydiscus marcianus.  These ammonites, found in Texas, USA are used by geologists and paleontologists as a zone marker for the Early Upper Albian Stage of the Cretaceous identified to 101 million years ago.  

This wonderful Eopachydiscus is a large and affordable example of an ammonite that thrived in the prehistoric sea that once covered what is not Texas in the U.S.A..  This extinct marine creature was alive when many well-known dinosaurs were walking the land.  This specimen has been repaired and reinforced on the reverse side to strengthen damage sustained during excavation.  Another smaller ammonite can be seen as a positive impression near the opening as seen in the last image above, at the bottom of the ammonite, slightly to the left.  Beautiful natural detail and intact centrum with life-like three-dimensional qualities!  We highly recommend this excellent example as it would make an interesting display fossil alongside North American dinosaur fossils or fossils of Mosasaurs, the primary predator that fed on these Cretaceous ammonites.

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.

HIGHLY DISPLAYABLE (AND AFFORDABLE) SPECIMEN FROM THE U.S.A.!

9.25" wide x 8" high

SOLD     AM-029    INCLUDES STAND     Actual Item - One Only

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