EVER WONDERED WHY WE FIND SO MANY SHARK TEETH IN THE FOSSIL RECORD?

 

Pliocene (~ 3million years old). teeth of great white shark carcharodon Linnaeus, 1758 from Antofagasta (Chile).

The abundance of shark teeth in the fossil record can be attributed to several key factors, including the unique biological characteristics of sharks, their evolutionary history, and the ecological dynamics of marine environments. These factors contribute to the high preservation potential of shark teeth, making them a common find in paleontological studies.

Eocene (approx. 50 million years old) sand tiger shark Striatolamia macrota Agassiz, 1843 from Khouribga phosphate deposits.

Biological Resilience

• Shark teeth are composed of highly durable materials, such as fluoroapatite and hydroxyapatite, which enhance their preservation over millions of years (Lübke et al., 2015).
• Sharks have a continuous tooth replacement system, shedding thousands of teeth throughout their lifetimes, leading to a significant accumulation of teeth in sedimentary depòsits (Bazzi et al., 2021).
  

Eocene shark tooth Otodus obliquus from Khouribga phosphate deposits (Morocco).

Evolutionary History

• Sharks have survived multiple mass extinction events, including the end-Cretaceous extinction, which has allowed for a rich fossil record that reflects their evolutionary adaptations (Bazzi et al., 2021).
• The morphological stability of shark teeth over time indicates their successful adaptation to various ecological niches, further contributing to their fossil presence (Lübke et al., 2015).

Miocene shark tooth Notorhynchus cepedianus from Belgium.

 

 Ecological Dynamics

• Changes in marine ecosystems, such as shifts in fish community structures and predator-prey dynamics, have influenced the abundance of shark teeth in the fossil record (Sibert, 2016).
• The fossil record shows a notable increase in shark teeth following significant global change events, suggesting a correlation between environmental shifts and tooth preservation (Sibert, 2016).

 Pliocene fossil shark tooth Carcharhinus egertoni Agassiz 1843 from #barcelona

Conversely, while shark teeth are prevalent in the fossil record, other marine vertebrates may not exhibit the same level of preservation due to differences in biological composition and ecological roles, highlighting the unique position of sharks in marine paleontology.

References

Bazzi M, Campione NE, Ahlberg PE, Blom H, Kear BP (2021) Tooth morphology elucidates shark evolution across the end-Cretaceous mass extinction. PLoS Biol 19(8): e3001108. https://doi.org/10.1371/journal.pbio.3001108

Lübke, A., Enax, J., Loza, K., Prymak, O., Gaengler, P., Fabritius, H. O., ... & Epple, M. (2015). Dental lessons from past to present: ultrastructure and composition of teeth from plesiosaurs, dinosaurs, extinct and recent sharks. Rsc Advances, 5(76), 61612-61622.

Sibert, E. C. (2016). Ichthyoliths as a paleoceanographic and paleoecological proxy and the response of open-ocean fish to Cretaceous and Cenozoic global change. University of California, San Diego.