Close-up of "leaf-pattern" chamber detail on surface seen above

VERY LARGE 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.  

A delicate shelled creature, usually these fossil ammonites are found deformed by pressure or partially crushed.  Full and complete examples are prized and large specimens such as this one from the United States are truly a magnificent find!  Ammonite possesses minor repair and minor restoration from a few hairline fractures and thin lower regions but is otherwise very full and complete.  The color variances are natural and the amber regions show a light remnant of the original shell.  In large areas on both sides, surface detail of the fascinating inner chambers is present and displays wonderfully.    

We highly recommend this excellent example.  Fine and large specimens from the USA are NOT common and not mined commercially compared to the much more prevalent Moroccan and Madagascar types always seen for sale.  This complete and monstrous specimen hails from the same time period as many of North America's famous dinosaurs and is a superbly preserved as well as a wonderfully aesthetic display fossil. 

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.

RARE, HUGE SIZE - HIGHLY DISPLAYABLE SPECIMEN FROM THE U.S.A.!

15.25" wide x 13.5" high

SOLD     AM-009    INCLUDES STAND     Actual Item - One Only

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