Ammonite Fossil with Tentacles 5.5" L x 5.0" W #3

Ammonite fossils are the preserved remains or impressions of ancient marine mollusks called ammonites. These fossils are typically found in sedimentary rocks, especially those formed during the Mesozoic Era, which spanned from approximately 250 to 66 million years ago. Ammonite fossils are renowned for their spiral-shaped shells, which are often beautifully preserved due to the durable nature of the calcium carbonate (aragonite) material from which they are composed.

Key characteristics of ammonite fossils include:

1. Spiral Shell: Ammonites had coiled, chambered shells that resembled a tightly wound coil, much like a modern nautilus shell but more complex and varied in form.

2. Chambered Structure: The shell is divided into multiple chambers separated by walls called septa. As the ammonite grew, it would continuously add new chambers, moving forward into the larger part of the shell, known as the living chamber.

3. Suture Patterns: The junctions where the septa meet the outer shell are called sutures. These suture patterns are highly intricate and varied among different species of ammonites, making them a key feature in identifying and classifying fossils.

4. Ribbing and Ornamentation: Many ammonite species had ribs or other ornamental patterns on their shells, which can also vary widely between species.

5. Size Variation: Ammonites ranged in size from less than a centimeter to over two meters in diameter, depending on the species.

Ammonite fossils are valuable to paleontologists and geologists because they provide insights into the ancient marine environments they inhabited, their evolutionary history, and clues about past climate and geography. They are often collected and studied for their scientific importance as well as their aesthetic appeal, making them popular among fossil enthusiasts and collectors.