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Ammonites are an extinct order of carnivorous mollusks that were closely related to the squid, octopus, cuttlefish, and the chambered nautilus. Ammonites mysteriously became extinct at the same time as the dinosaurs some 65 million years ago. The term "ammonite" means "Ammon's Stone." The name was given to these coiled fossils by the Egyptians who noted their resemblance to the horns of their ram headed god, Ammon. Ammonites flourished in oceans for approximately 330 million years.

Ammonites are easily recognized by their beautiful geometrically coiled shells. These shells were secreted by the animal and continued to grow and provide protection for the creature throughout its life. The animal itself probably very closely resembled a modern day squid living in the end of the shell (similar to the chambered nautilus). An ammonite could control its buoyancy much like a submarine, filling its chambers in the shell with either gas or fluid. Ammonites became so prolific that they filled nearly every niche in the ocean.

Many of the ammonites from South Dakota will fluoresce due to the replacement of the shell by calcite and chalcedony. The calcite will fluoresce from white to yellow to orange. The chalcedony usually shows up as a green fluorescence. Usually the stronger fluorescence is under long wave and is the first photo shown in the fluorescents (South Dakota) section of the web site. Chalcedony usually does not fluoresce well under long wave, but does fairly well for the fossils from this area.

Check out other South Dakota fluorescent offerings under the Fluorescents section. Then click on the "To view specimen material from South Dakota" link. Some other normal light photos will be shown there as well.

Rhaeboceras (rhaibos=bent + ceras=horn) occurs as medium to large size scaphitids with an involute phragmocone and a more evolute (loosely) coiled living chamber. The umbilical walls are fairly steep, the sides are slightly rounded, and the venter (outside edge) is very well rounded. Straight or slightly curving and bifurcated ribs are present on the sides. Tubercles may or may not be located near the umbilical or ventral areas. Most or the specimens offered here will be from the Upper Campanian Stage of the Upper Cretaceous (72-71 MYA).

This specimen is also available in the fluorescent section under South Dakota fluorescent minerals and fossils. It will have the same item number without the "N" at the end of the number.

This specimen has been sold! It was offered at $10.00.

Rhaeboceras
 
<i>Rhaeboceras</i> Quantity in Basket: None
Code: SDA-117N
Price: $0.00
Shipping Weight: 0.07 pounds
 
 
Quantity:
 
Time: Upper Cretaceous, Upper Campanian Stage, approximately 72-71 million years ago.
Location: Pierre Shale, South Dakota, USA
Dimensions: 1" x 3/4" x 7/16"

This specimen has been sold!



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