The Ammonites (Speetoniceras subinversum) - (Reference|Index} Fossils



Ammonites have actually been understood to humanity for countless 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 pictured as a man 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 been understood to humanity for thousands of years. The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites.

Ammonite Myths
Lots of cultures throughout history have actually associated unique powers to this fossil.

In ancient Greece, it was said that if you put an ammonite under your pillow it would cure 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 types had easy septa with a single arc like the members of the class orthocerida. Ammonites of later durations developed septa that had actually complex folds called saddles and lobes. They also established fragile lacey patterns on the outer shell. These patterns along with the shape of the shell and the structure of the septa are how this cephalopod is classified. Ammonites such as Speetoniceras subinversum are very desirable often on sale.

Because all living cephalopods (octopus, nautilus, and squid) are predators, we can presume that ammonites were. The only living cephalopod with an external shell is the chambered nautilus. It can swim and control its depth. It does this by using the siphuncle. The siphuncle is a tube that links all the chambers in the shell with the living animal. The nautilus can deduct or add gas in these chambers to manage buoyancy.

Ammonite Size
Ammonites have a vast array of size. Specimens have actually been found varying from less than a centimeter to 2 meters in size. Early ammonites, until the middle Jurassic, were smaller sized, usually less than 9 inches or 23 centimeters. During the upper Jurassic and lower Cretaceous bigger varieties can be found. Titanites discovered in the south of England can be over 50 centimeters, 2 feet in size.

Biostratigraphy
The tough shell of the ammonite was Find Out More quickly fossilized. This, combined with the sheer abundance of this group of cephalopods and its evolutionary duration through a number of geologic durations, make it a good index fossil. Index fossils assist geologists and paleontologists to determine the age of rock layers. This is called biostratigraphy. It works like this. If you find an ammonite from a genus understood to be from the Triassic Period, then the rock layer it originated from should be Triassic. To be a good index fossil:

It needs to have broad circulation.

There need to be a great deal of them.

It should come from web link a group that evolves rapidly.

They should be simple to acknowledge.

Ammonites satisfy all the above criteria easily.

Extinction of The Ammonites
The end of the Cretaceous Period was also the end of the ammonites. Dinosaurs and numerous other species of animals and plants died out at about this same time.

The curled ammonite shells looked like the horns and were called Ammon's hop over to these guys Stones or ammonites.

Ammonites of later durations developed septa that had elaborate folds called saddles and lobes. The hard shell of the ammonite was quickly fossilized. If you discover an ammonite from a genus understood to be from the Triassic Period, then the rock layer it came from should be Triassic. The end of the Cretaceous Period was likewise the end of the ammonites.

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