Ammonites have been known to mankind for thousands of years. They are the source of many stories and misconceptions. The name of this spiral-shelled cephalopod originates from the Egyptian god Ammon. Ammon was envisioned as a male with the horns of a ram extending from his head. The curled ammonite shells resembled the horns and were called Ammon's Stones or ammonites. Ammonites have been understood to humanity for thousands of years. The curled ammonite shells resembled the horns and were called Ammon's Stones or ammonites.
Many cultures throughout history have associated special powers to this fossil.
In ancient Greece, it was said that if you put an ammonite under your pillow it would treat insomnia and bring good dreams.
The Romans believed that if you put a golden ammonite (pryritized) under your pillow you would have prophetic dreams.
A Brief History of Ammonites
Ammonites initially appeared in the Devonian Period. Early curled species had basic septa with a single arc like the members of the class orthocerida. Ammonites of later durations developed septa that had actually complex folds called lobes and saddles. They also established delicate lacey patterns on the external shell. These patterns together with the shape of the shell and the structure of the septa are how this cephalopod is classified. Ammonites such as Russian Speetoniceras are very attractive often on auction.
Since all living cephalopods (nautilus, octopus, and squid) are predators, we can presume that ammonites were. The only living cephalopod with an external shell is the chambered nautilus. The siphuncle is a tube that connects all the chambers in the shell with the living animal.
Ammonites have a vast array of size. Specimens have actually been found ranging from less than a centimeter to 2 meters in diameter. Early ammonites, until the middle Jurassic, were smaller, typically less than 9 inches or 23 centimeters. Throughout the upper Jurassic and lower Cretaceous bigger ranges can be found. Titanites found in the south of England can be over 50 centimeters, 2 feet in diameter.
The this hyperlink difficult shell of the ammonite was quickly fossilized. This, combined with the sheer abundance of this group of cephalopods and its evolutionary duration through a number of geologic periods, make it a good index fossil. Index fossils assist paleontologists and geologists to determine the age of rock layers. This is called biostratigraphy. It works like this. The rock layer it came from should be Triassic if you discover an ammonite from a genus understood to be from the Triassic Period. To be a great index fossil:
It needs to have large distribution.
There must be a great deal of them.
It needs to belong to a group that evolves quickly.
They should be easy to acknowledge.
Ammonites satisfy all the above requirements easily.
Termination of The Ammonites
The end of the Cretaceous Period was likewise completion of the ammonites. This was about 65 million years earlier. Dinosaurs and numerous other species of animals and plants died out at about this very same time. It is thought that a huge meteor hitting earth caused these mass terminations.
The curled ammonite shells resembled the horns and were called Ammon's Stones or link ammonites.
Ammonites of later durations developed septa that had actually intricate folds called saddles and lobes. The hard shell of the ammonite was quickly fossilized. If you find an ammonite from a genus understood to be from the Triassic Period, then the rock layer it came from must be Triassic. The end of the Cretaceous Period was also the end of the ammonites.