The Ammonites to Collect - (Reference|Index} Fossils
Ammonites have been known to mankind for thousands of years. They are the source of many stories and myths. The name of this spiral-shelled cephalopod comes from the Egyptian god Ammon. Ammon was pictured as a male with the horns of a ram extending from his head. The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites. Ammonites have been known to humanity for thousands of years. The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites.
Numerous cultures throughout history have actually attributed unique powers to this fossil.
In ancient Greece, it was said that if you put an ammonite under your pillow it would treat sleeping disorders and bring good 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 initially appeared in the Devonian Period. Early curled species had easy septa with a single arc like the members of the class orthocerida. Ammonites of later durations established septa that had intricate folds called lobes and saddles. They likewise developed delicate lacey patterns on the external 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 from Russia are highly collectible fossils often on sale.
Since all living cephalopods (squid, octopus, and nautilus) are predators, we can presume that ammonites were too. The only living cephalopod with an external shell is the chambered nautilus. It can swim and manage its depth. It does this by using the siphuncle. The siphuncle is a tube that connects all the chambers in the shell with the living animal. The nautilus can add or subtract gas in these chambers to manage buoyancy.
Ammonites have a wide variety of size. Specimens have been found varying from less than a centimeter to 2 meters in diameter. Early ammonites, until the middle Jurassic, were smaller sized, normally less than 9 inches or 23 centimeters. Throughout the upper Jurassic and hop over to here lower Cretaceous larger varieties can be found. Titanites discovered in the south of England can be over 50 centimeters, 2 feet in diameter.
The tough shell of the ammonite was quickly fossilized. This, integrated with the large abundance of this group of cephalopods and its evolutionary period through a number of geologic durations, make it a great index fossil. Index fossils help paleontologists and geologists to figure out 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 originated from need to be Triassic. To be a great index fossil:
It needs to have large circulation.
There must be a lot of them.
It must belong to a group that evolves rapidly.
They need to be easy to recognize.
Ammonites please all the above criteria easily.
Termination of The Ammonites
Completion of the Cretaceous Period was also completion of the ammonites. This had to do with 65 million years earlier. Dinosaurs and lots of other species of animals and plants passed away out at about this very same time. It is thought that a substantial meteor colliding with earth caused these mass extinctions.
The curled ammonite shells looked like the horns and were called Ammon's Stones or ammonites.
Ammonites of later durations developed septa that had complex folds called lobes and saddles. The tough shell of the ammonite was easily fossilized. If you discover an ammonite from a genus known to be from the Triassic Period, then the rock layer it came my latest blog post from should be Triassic. The end of the Cretaceous Period was likewise the end of the ammonites.