Ammonites: Fossil treasures of the past 

1. Introduction

 

Ammonites are among the most iconic fossils of the prehistoric world. These now extinct marine mollusks populated the oceans for over 300 million years, before becoming extinct along with the dinosaurs at the end of the Cretaceous. Their spiral shells, often well preserved, fascinate scientists and collectors alike. But what do we really know about these creatures? This article explores their origin, morphology, lifestyle, and importance in Earth's history. We offer plenty of ammonites for sale on our website. 

2. Origin and classification  

Ammonites belong to the class Cephalopoda, just like modern squid and cuttlefish. They appeared during the Devonian period, about 400 million years ago. They are descended from Bactrites, a group of mollusks with straight shells. Ammonites quickly diversified into a multitude of species, adapted to different marine environments. Their classification is mainly based on the shape and structure of their shell, with several distinct orders such as Goniatitida, Ceratitida and Ammonitida.  

The evolution of ammonites has been marked by significant transformations over geological periods. The first forms, the goniatites, had relatively simple sutures, while more recent ammonites developed increasingly complex sutures, which gave them better resistance to marine pressures. This rapid evolution allowed them to adapt to varied environments and exploit many ecological niches.

3.Morphology and characteristics

The main characteristic of ammonites is their spirally coiled shell. Made of calcium carbonate, it had internal chambers, called septa, which allowed them to control their buoyancy thanks to a siphon system. Unlike modern nautiluses, ammonites had complex sutures marked by wavy lines, making them even more fascinating to paleontologists. Their size ranged from a few centimeters to several meters for some giant species. Ammonites also had tentacles that they used to capture prey, a horny beak similar to that of modern octopuses, and a mode of propulsion based on the projection of water, a characteristic common to modern cephalopods. It is assumed that they were fearsome predators or opportunistic scavengers, feeding on small fish, crustaceans and other marine invertebrates.

4.Environment and Geographic Distribution

Ammonites have occupied almost all marine environments, from coastal waters to deeper areas. Their fossils are now found worldwide, particularly in sedimentary rocks dating from the Jurassic and Cretaceous periods. Their wide distribution and rapid evolution make them excellent stratigraphic markers, allowing geologists to precisely date certain terrestrial layers.  

Environmental conditions played a key role in their diversification. Periods of high ammonite biodiversity often coincide with phases of warm climate and high sea levels. Conversely, periods of mass extinction were marked by environmental upheavals, such as drops in temperature, lower sea levels or anoxic events in the oceans.  

5. Ammonites lifestyle

 

Ammonites played a central role in marine ecosystems, acting as both predators and prey. As cephalopods, they were likely active and mobile, using water jet propulsion to move quickly through the water column. Their ability to adjust their buoyancy through internal chambers in their shells allowed them to navigate between different depths with ease. 

Ammonites had a varied diet. Their powerful horny beaks allowed them to capture crustaceans, small fish, and other marine invertebrates. Some smaller species likely fed on plankton, adopting a lifestyle similar to that of modern nautiluses. Their hunting strategy was likely similar to that of modern squid and cuttlefish, using their tentacles to grasp prey and pull it into their mouths.  

Ammonites were also prey for many marine predators. Fossilized bite marks on some shells suggest that they were the target of large marine reptiles such as mosasaurs and pliosaurs. Their robust shells offered them some protection, but when faced with specialized predators, they often had no escape.  

When it comes to reproduction, ammonites probably adopted a strategy similar to that of modern cephalopods. Females would have laid large numbers of floating eggs in the open sea, allowing their larvae to drift with the ocean currents before reaching a juvenile stage. This strategy of mass reproduction would have contributed to their wide distribution in the world's oceans and their incredible diversity. Their lifestyle also influenced their geographic distribution. Some species were adapted to deep waters, while others preferred shallow coastal areas. Their diversity and adaptation to environmental change contributed to their evolutionary success for millions of years, before the cataclysmic events of the Cretaceous ended their reign.  

6.Ammonites Extinction

Ammonites survived several biological crises before disappearing at the end of the Cretaceous period, about 66 million years ago. This extinction, often attributed to the impact of an asteroid on the Yucatan Peninsula, led to climate change and ocean acidification that were fatal to ammonites. Unlike their cousins, the nautiluses, they were unable to survive the post-cataclysmic conditions. 

In addition to the asteroid impact, intense volcanism, including the eruptions of the Deccan Traps in India, contributed to changing the chemical composition of the oceans, disrupting the marine food chain. Ammonites, which depended on a stable ecological balance, were unable to adapt to these abrupt changes. 

7.Paleontological Importance and Use

Ammonites play a crucial role in paleontology. Their abundance and rapid evolution allow for precise dating of sedimentary rocks. They are used as stratigraphic fossils, helping geologists identify specific geological layers and reconstruct the history of past oceans. 

Apart from their scientific interest, they are also highly prized in jewelry and decoration. Some fossilized species have shimmering plays of color due to the mineral transformation of their shells, making them sought-after objects. Iridescent ammonites, particularly those discovered in Alberta (Canada), are transformed into gems called ammolites, prized for their exceptional brilliance.  

Ammonites have also played a role in beliefs and folklore. In some cultures, they were seen as lucky charms or stones with protective properties. In England, they were once called "stone snakes" because their spiral shape was reminiscent of a coiled snake. * 

8.Great Discoveries and Remarkable Specimens  

Some ammonite discoveries are particularly notable. One of the largest known ammonites, Parapuzosia seppenradensis, was discovered in Germany and measures over 2.5 meters in diameter. Exceptionally well-preserved fossils, found in anoxic conditions, have also made it possible to study the internal structure of ammonites and even, in some cases, to identify remains of soft tissues. 

 

In France, deposits such as those in the Argonne region or the cliffs of Normandy are full of remarkable ammonite fossils, contributing to the richness of European paleontological heritage.  

9. Emblematic Deposits and Collection

Fossil enthusiasts and collectors can find ammonites in several renowned sites around the world. Among the most famous are the cliffs of Lyme Regis in England, part of the Jurassic Coast, where Mary Anning discovered many marine fossils. In France, the deposits of Aveyron and Alsace are full of well-preserved ammonites. Some of those ammonites are for sale on our website. Canada, particularly in Alberta, offers opalized ammonites, with spectacular iridescent reflections, prized in jewelry. Other sites such as Morocco and Madagascar are known for the abundance and variety of their specimens. These places are paradises for enthusiasts, allowing them to explore the history of the Earth through these fascinating fossils.  

10.Fossilization and Preservation of Ammonites

Fossilization of ammonites is a process that spans millions of years. After their death, their shells fell to the bottom of the ocean and were gradually covered by sediment. Over time, minerals contained in the water penetrated the shell and gradually replaced its original structure, resulting in the formation of a fossil. Some ammonites have been preserved in exceptional conditions, with remarkably preserved internal details. Sometimes, specific mineralizations, such as pyritization, give the fossils a golden sheen, making them particularly sought-after objects by collectors.  

Ammonites are often used as stratigraphic fossils because of their wide distribution and rapid evolution. They allow geologists to precisely date the rock layers in which they are found, thus providing valuable information on the geological history of the Earth.  

11.Evolution of suture lines in ammonites  

A fascinating aspect of ammonite evolution is the progressive complexity of their suture lines. Sutures correspond to the lines formed by the intersection of internal septa with the shell wall. In primitive ammonites, such as Devonian and Carboniferous goniatites, these lines were relatively simple and angular. Over time, sutures evolved into increasingly elaborate patterns, reaching a maximum complexity in Cretaceous ammonites. 

This evolution of suture lines is often interpreted as an adaptation to strengthen the shell against marine pressures. The more complex the sutures, the more resistant the shell was to mechanical stresses and to the pressures exerted by the deep sea. This characteristic allowed ammonites to colonize a wide range of habitats, from shallow waters to the abyss. 

  Furthermore, the study of sutures is crucial for the classification of ammonites. Paleontologists use these patterns to identify different species and establish evolutionary relationships between them. These structures are therefore a valuable tool for understanding the evolutionary history of ammonites and their progressive adaptation to their environment. 

Conclusion

 

Ammonites are much more than simple fossils: they are witnesses of a bygone era and valuable clues to understanding the history of our planet. Their study continues to fascinate scientists and paleontology enthusiasts. By revealing the secrets of the past, they help us better understand the ecological and evolutionary dynamics of the living world. Ammonite fossils have given us a deeper understanding of ancient oceans and their biodiversity. These extraordinary marine creatures continue to inspire researchers and fossil enthusiasts around the world, reminding us that every rock holds a fascinating story waiting to be uncovered.

Ammonites: Fossil treasures of the past 

1. Introduction

 

Ammonites are among the most iconic fossils of the prehistoric world. These now extinct marine mollusks populated the oceans for over 300 million years, before becoming extinct along with the dinosaurs at the end of the Cretaceous. Their spiral shells, often well preserved, fascinate scientists and collectors alike. But what do we really know about these creatures? This article explores their origin, morphology, lifestyle, and importance in Earth's history. We offer plenty of ammonites for sale on our website. 

2. Origin and classification  

Ammonites belong to the class Cephalopoda, just like modern squid and cuttlefish. They appeared during the Devonian period, about 400 million years ago. They are descended from Bactrites, a group of mollusks with straight shells. Ammonites quickly diversified into a multitude of species, adapted to different marine environments. Their classification is mainly based on the shape and structure of their shell, with several distinct orders such as Goniatitida, Ceratitida and Ammonitida.  

The evolution of ammonites has been marked by significant transformations over geological periods. The first forms, the goniatites, had relatively simple sutures, while more recent ammonites developed increasingly complex sutures, which gave them better resistance to marine pressures. This rapid evolution allowed them to adapt to varied environments and exploit many ecological niches.

3.Morphology and characteristics

The main characteristic of ammonites is their spirally coiled shell. Made of calcium carbonate, it had internal chambers, called septa, which allowed them to control their buoyancy thanks to a siphon system. Unlike modern nautiluses, ammonites had complex sutures marked by wavy lines, making them even more fascinating to paleontologists. Their size ranged from a few centimeters to several meters for some giant species. Ammonites also had tentacles that they used to capture prey, a horny beak similar to that of modern octopuses, and a mode of propulsion based on the projection of water, a characteristic common to modern cephalopods. It is assumed that they were fearsome predators or opportunistic scavengers, feeding on small fish, crustaceans and other marine invertebrates.

4.Environment and Geographic Distribution

Ammonites have occupied almost all marine environments, from coastal waters to deeper areas. Their fossils are now found worldwide, particularly in sedimentary rocks dating from the Jurassic and Cretaceous periods. Their wide distribution and rapid evolution make them excellent stratigraphic markers, allowing geologists to precisely date certain terrestrial layers.  

Environmental conditions played a key role in their diversification. Periods of high ammonite biodiversity often coincide with phases of warm climate and high sea levels. Conversely, periods of mass extinction were marked by environmental upheavals, such as drops in temperature, lower sea levels or anoxic events in the oceans.  

5. Ammonites lifestyle

 

Ammonites played a central role in marine ecosystems, acting as both predators and prey. As cephalopods, they were likely active and mobile, using water jet propulsion to move quickly through the water column. Their ability to adjust their buoyancy through internal chambers in their shells allowed them to navigate between different depths with ease. 

Ammonites had a varied diet. Their powerful horny beaks allowed them to capture crustaceans, small fish, and other marine invertebrates. Some smaller species likely fed on plankton, adopting a lifestyle similar to that of modern nautiluses. Their hunting strategy was likely similar to that of modern squid and cuttlefish, using their tentacles to grasp prey and pull it into their mouths.  

Ammonites were also prey for many marine predators. Fossilized bite marks on some shells suggest that they were the target of large marine reptiles such as mosasaurs and pliosaurs. Their robust shells offered them some protection, but when faced with specialized predators, they often had no escape.  

When it come to reproduction, ammonites probably adopted a strategy similar to that of modern cephalopods. Females would have laid large numbers of floating eggs in the open sea, allowing their larvae to drift with the ocean currents before reaching a juvenile stage. This strategy of mass reproduction would have contributed to their wide distribution in the world's oceans and their incredible diversity. Their lifestyle also influenced their geographic distribution. Some species were adapted to deep waters, while others preferred shallow coastal areas. Their diversity and adaptation to environmental change contributed to their evolutionary success for millions of years, before the cataclysmic events of the Cretaceous ended their reign.  

6.Ammonites Extinction

Ammonites survived several biological crises before disappearing at the end of the Cretaceous period, about 66 million years ago. This extinction, often attributed to the impact of an asteroid on the Yucatan Peninsula, led to climate change and ocean acidification that were fatal to ammonites. Unlike their cousins, the nautiluses, they were unable to survive the post-cataclysmic conditions. 

In addition to the asteroid impact, intense volcanism, including the eruptions of the Deccan Traps in India, contributed to changing the chemical composition of the oceans, disrupting the marine food chain. Ammonites, which depended on a stable ecological balance, were unable to adapt to these abrupt changes. 

7.Paleontological Importance and Use

Ammonites play a crucial role in paleontology. Their abundance and rapid evolution allow for precise dating of sedimentary rocks. They are used as stratigraphic fossils, helping geologists identify specific geological layers and reconstruct the history of past oceans. 

Apart from their scientific interest, they are also highly prized in jewelry and decoration. Some fossilized species have shimmering plays of color due to the mineral transformation of their shells, making them sought-after objects. Iridescent ammonites, particularly those discovered in Alberta (Canada), are transformed into gems called ammolites, prized for their exceptional brilliance.  

Ammonites have also played a role in beliefs and folklore. In some cultures, they were seen as lucky charms or stones with protective properties. In England, they were once called "stone snakes" because their spiral shape was reminiscent of a coiled snake. * 

8.Great Discoveries and Remarkable Specimens  

Some ammonite discoveries are particularly notable. One of the largest known ammonites, Parapuzosia seppenradensis, was discovered in Germany and measures over 2.5 meters in diameter. Exceptionally well-preserved fossils, found in anoxic conditions, have also made it possible to study the internal structure of ammonites and even, in some cases, to identify remains of soft tissues. 

 

In France, deposits such as those in the Argonne region or the cliffs of Normandy are full of remarkable ammonite fossils, contributing to the richness of European paleontological heritage.  

9. Emblematic Deposits and Collection

Fossil enthusiasts and collectors can find ammonites in several renowned sites around the world. Among the most famous are the cliffs of Lyme Regis in England, part of the Jurassic Coast, where Mary Anning discovered many marine fossils. In France, the deposits of Aveyron and Alsace are full of well-preserved ammonites. Some of those ammonites are for sale on our website. Canada, particularly in Alberta, offers opalized ammonites, with spectacular iridescent reflections, prized in jewelry. Other sites such as Morocco and Madagascar are known for the abundance and variety of their specimens. These places are paradises for enthusiasts, allowing them to explore the history of the Earth through these fascinating fossils.  

10.Fossilization and Preservation of Ammonites

Fossilization of ammonites is a process that spans millions of years. After their death, their shells fell to the bottom of the ocean and were gradually covered by sediment. Over time, minerals contained in the water penetrated the shell and gradually replaced its original structure, resulting in the formation of a fossil. Some ammonites have been preserved in exceptional conditions, with remarkably preserved internal details. Sometimes, specific mineralizations, such as pyritization, give the fossils a golden sheen, making them particularly sought-after objects by collectors.  

Ammonites are often used as stratigraphic fossils because of their wide distribution and rapid evolution. They allow geologists to precisely date the rock layers in which they are found, thus providing valuable information on the geological history of the Earth.  

11.Evolution of suture lines in ammonites  

A fascinating aspect of ammonite evolution is the progressive complexity of their suture lines. Sutures correspond to the lines formed by the intersection of internal septa with the shell wall. In primitive ammonites, such as Devonian and Carboniferous goniatites, these lines were relatively simple and angular. Over time, sutures evolved into increasingly elaborate patterns, reaching a maximum complexity in Cretaceous ammonites. 

This evolution of suture lines is often interpreted as an adaptation to strengthen the shell against marine pressures. The more complex the sutures, the more resistant the shell was to mechanical stresses and to the pressures exerted by the deep sea. This characteristic allowed ammonites to colonize a wide range of habitats, from shallow waters to the abyss. 

  Furthermore, the study of sutures is crucial for the classification of ammonites. Paleontologists use these patterns to identify different species and establish evolutionary relationships between them. These structures are therefore a valuable tool for understanding the evolutionary history of ammonites and their progressive adaptation to their environment. 

Conclusion

 

Ammonites are much more than simple fossils: they are witnesses of a bygone era and valuable clues to understanding the history of our planet. Their study continues to fascinate scientists and paleontology enthusiasts. By revealing the secrets of the past, they help us better understand the ecological and evolutionary dynamics of the living world. Ammonite fossils have given us a deeper understanding of ancient oceans and their biodiversity. These extraordinary marine creatures continue to inspire researchers and fossil enthusiasts around the world, reminding us that every rock holds a fascinating story waiting to be uncovered.