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Above: Front of Specimen Card
Ammonites are an extinct group of cephalopods that entered the fossil record 400 million years ago. They survived several mass extinction events, including the Permian–Triassic "Great Dying" which wiped out 96% of all marine species. They finally succumbed during the Cretaceous-Paleogene extinction event 66 million years ago, which also wiped out the dinosaurs.
This specimen is a fossilized ammonite shell from Madagascar. There are two styles: split and whole.
Above: A sampling of all available sizes and styles.
Split specimens are precision cut to reveal the interior spiral.
Above: A large split specimen.
Whole specimens are suitable for tabletop display. They range in size from 3cm to 5cm in diameter. The outer surface is polished to reveal the sutures in the shell.
Above: Two whole specimens.
All specimens come inside our classic, glass-topped riker display cases. The cases measure 4 1/2" x 3 1/2". A small information card is also enclosed that also serves as the certificate of authenticity.
More about Ammonites
"Three times during their reign of more than 300 million years, ammonites experimented with the most bizarre and startling shell shapes."
~ Wolfgang Grulke, author of "Heteromorph: The Rarest Fossil Ammonites"
Many thousands of distinct species make up the long-lived ammonoid clade. Though most ammonite shells are the classic spiral, there are also straight and gastropod-like shells and even some shells that are partially uncoiled. The surface of the shells also vary quite widely from smooth to wildly thorny.
The size of ammonite shells range from sub-centimeter dwarf species to giants nearly three meters in diameter. Most iconic shells exhibit a nearly perfect logarithmic spiral.
Aside from their complex shells, there is little direct evidence regarding the appearance of ammonites due to the absence of soft-tissue fossils. However, many scientists believe ammonites had bodies similar to that of the present-day Nautilus.
The main property of a logarithmic spiral is that the shape of the spiral is unaltered as it increases in size. Each turn is a pure geometrical progression of the last with a common ratio. This form is found in many natural phenomena, from the shape of galaxies to patterns on sunflower heads.
How these creatures lived is of intense interest to science as ammonites likely played a vital role in the food chain in the ancient seas. Evidence exists to suggest that ammonites were a prime food source for Mosasaurs and fishes, while other studies suggest the "bite marks" were created after death by limpets or even by other cephalopods.
Above: Back of Specimen Card