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



Ammonites have been understood to humanity for thousands of years. They are the source of many stories and misconceptions. The name of this spiral-shelled cephalopod comes 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.

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.

If you put a golden ammonite (pryritized) under your pillow you would have prophetic dreams, the Romans believed that.

A Brief History of Ammonites
Ammonites first appeared in the Devonian Period. Ammonites of later durations established septa that had elaborate folds called lobes and saddles. Ammonites such as Speetoniceras are very beautiful often on auction.

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 using the siphuncle. The siphuncle is a tube that read what he said links all the chambers in the shell with the living animal. The nautilus can add or subtract gas in these chambers to control buoyancy.

Ammonite Size
Ammonites have a large variety of size. Early ammonites, till the middle Jurassic, were smaller sized, generally less than 9 inches or 23 centimeters.

Biostratigraphy
The hard shell of the ammonite was easily fossilized. This, combined with the sheer abundance of this group of cephalopods and its evolutionary period through numerous geologic durations, make it a good index fossil. Index fossils assist geologists and paleontologists to figure out the age of rock layers. This is called biostratigraphy. It works like this. The rock layer it came from should be Triassic if you find an ammonite from a genus known to be from the Triassic Period. To be an excellent index fossil:

It must have large distribution.

There need to be a great deal of them.

It should belong to a group that progresses rapidly.

They must be simple to recognize.

Ammonites satisfy all the above criteria quickly.

Termination of The Ammonites
The end of the Cretaceous Period was also the end of the ammonites. This had to do with 65 million years back. Dinosaurs and many other types of plants and animals passed away out at about this same time. It is believed that a big meteor colliding with earth triggered these mass extinctions.

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

Ammonites of later periods established septa that had complex folds called lobes and saddles. The difficult shell of the ammonite was easily fossilized. If you find an ammonite from a genus understood to be from the Triassic Period, then the rock layer it came from Full Report need to be Triassic. The end of the Cretaceous Period was also the end of the ammonites.

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