SUPERB NATURAL WHITE AMMONITE GROUP WITH INTACT PEARLY SHELLS FROM THE UNITED STATES PIERRE SHALE

Pierre Shale - South Dakota, U.S.A.

UPPER CRETACEOUS PERIOD:  73 million years ago

With immense natural aesthetics, this is a large portion of an original ammonite-bearing shale boulder displaying two complete (as well as multiple other partials) of beautiful natural white Upper Cretaceous ammonites.  The two primary ammonites shown are a variety of Jeletzkytes sp. and Scaphites sp. ammonites.  Most impressive is the presence of their original preserved shells that are thick and white with multi-colored, pearly iridescence seen in full light.  This effect did not photograph but is very obvious in person and must be seen as such to be appreciated.  This specimen is much, much nicer in person!  The original outer rind of the boulder is also still present.  This is a fantastic display piece with lots of educational value as well, since the matrix is large and has not been ground away and removed.  This shows what the original rock looked like where these rare ammonites were found.  Ammonites like these are not commercially mined so their scarcity is not only due to true rarity but also to the lack of any large scale efforts compared to mass-marketed and produced ammonites from Russia, Madagascar and Morocco.  Excellent horned anatomy is preserved as well as very delicate chamber detail.  Natural as found with 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.

UNCOMMON SPECIMEN WITH RARE PRESERVED FOSSIL SHELL AND PEARLY, IRIDESCENT NACRE!!!

10" x 6.75" overall in matrix, largest ammonite is 4.2' across

$895     AMX-102     Actual Item - One Only

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895