Fossil Notes - Ammonite
Ammonite
Classification: Class Cephalopoda, Subclass Ammonoidea
Origin
Ammonites are marine creatures that first appeared in the Devonian period, approximately 400 million years ago.
They belong to the same group as octopuses and squids, the cephalopods, and possessed a hard outer shell.
Most are thought to have lived in warm, shallow seas, gently floating and protecting themselves from predators.
They quietly vanished from Earth at the end of the Cretaceous period, about 66 million years ago, amidst a major upheaval.
Structure
The ammonite shell consists of three elements: the outer shell, septa, and siphuncle.
The interior was divided into small chambers called "camerae," and they adjusted their buoyancy by changing the amount of gas and liquid within these chambers.
Their spiral shape follows a logarithmic spiral, growing in a ratio close to the Fibonacci sequence.
As one of the orders created by nature, it remains a fascinating subject for many researchers today.
Fossilization
After death, their shells sank to the seabed and were enveloped by sediment, entering a long slumber.
Over vast stretches of time, organic matter was replaced by minerals, preserving their form as fossils.
The main minerals involved in this replacement include calcite, pyrite, and silica, and the color and texture vary depending on the environment.
In Morocco and Madagascar, beautiful specimens are still being found due to the uplift of geological strata.
Scientific Value
Ammonites evolved rapidly, and their appearance changed significantly with each era.
Because of this, they are widely used as "index fossils" to determine the age of geological strata.
They are indispensable for research in geology and paleontology,
and each specimen provides a clue to understanding Earth's history.
