The Ammonites (such as Speetoniceras from Russia) - (Reference|Index} Fossils



Ammonites have been known to mankind for thousands of years. They are the source of lots of stories and misconceptions. The name of this spiral-shelled cephalopod originates from the Egyptian god Ammon. Ammon was visualized as a guy with the horns of a ram protruding from his head. The curled ammonite shells resembled the horns and were called Ammon's Stones or ammonites. Ammonites have actually been understood to mankind for thousands of years. The curled ammonite shells resembled the horns and were called Ammon's Stones or ammonites.

Ammonite Myths
Lots of cultures throughout history have attributed special powers to this fossil.

In ancient Greece, it was stated that if you put an ammonite under your pillow it would cure insomnia and bring excellent dreams.

The Romans thought that if you put a golden ammonite (pryritized) under your pillow you would have prophetic dreams.

A Brief History of Ammonites
Ammonites first appeared in the Devonian Period. Early curled types had easy septa with a single arc like the members of the class orthocerida. Ammonites of later periods established septa that had intricate folds called saddles and lobes. They likewise developed fragile lacey patterns on the outer shell. These patterns in addition to the shape of the shell and the structure of the septa are how this cephalopod is categorized. Ammonites such as Russian Speetoniceras are highly collectible fossils often on auction.

Given that all living cephalopods (squid, nautilus, and octopus) are predators, we can presume that ammonites were. The only living cephalopod with an external shell is the chambered nautilus. see this page The siphuncle is a tube that links all the chambers in the shell with the living animal.

Ammonite Size
Ammonites have a broad range of size. Early ammonites, up until the middle Jurassic, were smaller sized, generally less than 9 inches or 23 centimeters.

Biostratigraphy
The tough shell of the ammonite was quickly fossilized. This, combined with the sheer abundance of this group of cephalopods and its evolutionary period through a number of geologic durations, make it a good index fossil. Index fossils help paleontologists and geologists to identify the age of rock layers. This is called biostratigraphy. It works like this. If you find an ammonite from a genus known to be from the Triassic Period, then the rock layer it came from must be Triassic. To be an excellent index fossil:

It should have wide circulation.

There should be a lot of them.

It needs to come from a group here that evolves quickly.

They need to be easy to acknowledge.

Ammonites please all of the above criteria quickly.

Termination of The Ammonites
The end of the Cretaceous Period was likewise the end of the ammonites. Dinosaurs and many other types of plants and animals passed away out at about this same time.

The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites.

Ammonites of later periods developed septa that had actually elaborate folds called saddles and lobes. The difficult 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 need to be Triassic. The end of the Cretaceous Period was also the end of the ammonites.

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