Discoscaphites conradi
Geological Time: Upper Cretaceous
Size (25.4 mm = 1 inch): 70 mm, 53 mm, 23 mm, and 18 mm across on a 175 mm by 95 mm and 145 mm by 120 mm matrix base
Fossil Site: Fox Hills Formation, North Central South Dakota
Fossil Code: FH010
Price: $395.00 - sold
 Description:
A magnificent example of an assemblage of the ammonite Discoscaphites
conradi of the Fox Hills Formation deposits of South Dakota. During
the Cretaceous, much of the Western United States was covered by what
is termed the Western Interior Seaway, a broad shallow (100-300 m
maximum depth) sea that was home to various aquatic reptiles, fish,
and ammonites. It was open to the North to Canada’s boreal seas
and to the South to what is now the present-day Gulf of Mexico. During
the Late Cretaceous, fluctuations in the sea level led to various
bouts of exposure of some regions; as a consequence, there is some
intertonguing of terrestrial deposits, the most famous of which is
Hell Creek, home of T. rex. Ammonites of this degree of preservation
are difficult to come across singly, much less as a multiple as seen
here. In addition to the complete examples, there are numerous bivalves.
The high degree of preservation of their natural mother-of-pearl shell
makes them appear to be preserved as opal. This is a consequence of
light passing through the various layers of aragonite and conchiolin
deposited by the ammonite in life. Conchiolin is secreted by various
other mollusks, including oysters, and is a complex protein. Notice
how the colors change with changing perspective. This is a stunning
example a death assemblage of this flashy ammonite. Some modern-day
cephalopods are known to come together for mating, only to die soon
thereafter. Perhaps this is the fate that befell these beautiful examples
preserved here. The preservation of the shell in the cast of the largest
specimen makes for a stunning display for home or office. |
