UNDERSTANDING AMMONOIDS: THE ANCIENT MASTERS OF BUOYANCY

 

What are ammonoids?: Ammonoids are a group of extinct marine animals related to modern squids and octopuses. They are best known for their spiral-shaped shells, which are often found as fossils. These creatures lived in the oceans for over 300 million years and are considered iconic fossils due to their unique shell structures and evolutionary history.

The structure of their shells: The shells of ammonoids are divided into chambers, which are separated by walls called septa. These septa have complex internal architectures that evolved over time, becoming more intricate as ammonoids adapted to their environments. The complexity of these structures is a key feature that scientists study to understand their biology and evolution.

 

Buoyancy control: One of the most fascinating aspects of ammonoid biology is how they controlled their buoyancy. The septa within their shells are not just for structure; they play a crucial role in helping the animal float and move in the water. The folds and shapes of these septa can retain liquid, which is essential for buoyancy regulation. This means that ammonoids could adjust their position in the water column, helping them to avoid predators and find food.

 

Recent research findings: Recent studies using 3D-printed models have shown that ammonoids with more complex septa can hold more liquid due to better surface tension. This ability to retain liquid is vital for buoyancy control, allowing these ancient creatures to thrive in various marine environments. The research suggests that ammonoids with intricate shell designs had a significant advantage over those with simpler structures.

Creation of cylindrical shells models (a–c) and chamber models (d–f) used in liquid retention experiments. (a) Wireframe view showing the suture (orange) wrapped around the internal whorl section. (b)   Extruded, virtual model with the cylindrical shell and septum unied together. (c) Final 3D printed model used to measure the liquid retained by surface tension in the septal recesses. (d) Virtual model of a single chamber (camera). (e) Virtual model of the camera subtracted from a bounding volume.(f) Final, 3D printed model with empty chamber inside and holes for drainage on the adoral, adapical, and ventral sides of the model (Peterman et al, 2021)

Ecological Importance: Understanding how ammonoids managed their buoyancy provides insights into their ecological roles in ancient marine ecosystems. Their adaptations allowed them to survive and flourish during significant evolutionary changes, making them key players in the history of life on Earth.

In summary, ammonoids are remarkable examples of evolutionary success, showcasing how complex structures can lead to better survival strategies in changing environments. Their story continues to captivate scientists and enthusiasts alike!

More info: David, J., Peterman., Kathleen, A., Ritterbush., Charles, N., Ciampaglio., Erynn, H., Johnson., Shinya, Inoue., Tomoyuki, Mikami., Thomas, Linn. (2021). Buoyancy control in ammonoid cephalopods refined by complex internal shell architecture.. Scientific Reports, 11(1):8055-8055. doi: 10.1038/S41598-021-87379-5.