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.

This specimen is also offered in the fluorescent section under South Dakota fluorescent minerals and fossils. Also 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.

The two main fossils on this specimen are Hoploscaphites and Jeletzkytes. Both are beautiful representations of their species. The Jeletzkytes is the specimen, in the shadow to the right.

Hoploscaphites (hoplo=heavily armored foot soldier + skaphe=boat + ites=a stone). They have compressed or flattened sides. The phragmocone is tightly coiled, with shallow umbilical walls and a short, slightly curved body chamber. Ribs tend to be thicker on the phragmocone, becoming denser and finer on the body chamber. The ribs often bifurcate (divide) and bend back towards the phragmocone at mid-flank. Small ventrolateral tubercles (bumps) may be present on the body chamber and may or may not be present along the umbilical margin. They lived during the Campanian and Maastrichtian Stages (100-70 MYA).

Jeletzkytes can occur as small to large moderately inflated conchs. So, compared to Hoploscaphites it will appear to be somewhat fatter. The phragmocone (the walled off part of the shell) has an involute (tight) coil. The body chamber has a short shaft which extends slightly from the phragmocone and re-curves slightly back towards the phragmocone. Ribbing is sparse and straight on the phragmocone and tends to bifurcate and bend slightly on the living chamber. Prominent ventrolateral nodes are present on the phragmocone which fade away as they approach the opening of the living chamber. Many species have at least one more row of tubercles near the umbilical margin or midway on the sides. Jeletzkytes from the area where this specimen was found occurred from the Middle Campanian through Maastrichtian Stages of the Upper Cretaceous (about 80-70 MYA).

Hoploscaphites and Jeletzkytes
	Quantity in Basket: None Code: SDA-102N Price: $75.00 Shipping Weight: 1.74 pounds
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Time: Upper Cretaceous, Middle Campanian through Maastrichtian Stages, approximately 80-70 million years ago. Location: Pierre Shale, South Dakota, USA Dimensions: 4-1/2" x 3-3/4" x 2-7/8"