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Understanding The Largest Known Prehistoric Turtle From 80 Million Years Ago

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Author Arwen Kent, Bachelor of Science

A man beside the skeleton of archelon.
A man beside the skeleton of archelon. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0

Read all the way to the end – we save the one detail most people never think about for last.

Archelon was a giant prehistoric turtle that lived during the Late Cretaceous period, around 80 to 66 million years ago. This sea turtle is the largest known turtle species to have ever existed. Let’s look at how Archelon fossils have provided incredible insights into its life and environment!

The First Discovery of Archelon

Full skeleton of archelon the prehistoric turtle.
Full skeleton of Archelon the prehistoric turtle. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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The first Archelon specimen was discovered in South Dakota in 1895 by Dr. George Reber Wieland. Specifically, the fossil was found in the Pierre Shale Formation, a rich fossil site from the Cretaceous period. Both then and now, this discovery sparked great interest among paleontologists!

Size of Archelon

Archelon skeleton.
Archelon skeleton. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon was truly massive, measuring up to 15 feet long and weighing around 5,000 pounds. Undoubtedly, its size made it one of the most imposing creatures of the ancient seas. As I imagine you’ve already noticed, it was much larger than modern sea turtles!

Shell Structure

Skull of archelon.
Skull of Archelon. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Unlike most turtles, Archelon had a leathery shell instead of a hard one. This is because its shell, or carapace, was lighter and more flexible, which likely helped it swim more easily in the ocean. Additionally, the shell’s design provided some protection from prehistoric predators.

Habitat and Environment

Archelon and a man for scale.
Archelon and a man for scale. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon lived in the shallow seas that covered much of North America during the Late Cretaceous. Moreover, these waters were full of marine life, making it a perfect habitat for this giant turtle to live and hunt. Archelon likely swam long distances in search of food, as its massive size likely meant it was often hungry.

Diet of Archelon

Archelon resting on a beach.
Archelon resting on a beach. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon was a carnivore, feeding mainly on jellyfish, mollusks, and other soft-bodied creatures. Consequently, it had a powerful beak that allowed it to crush and consume its prey. Interestingly, this diet was similar to what many modern sea turtles eat today, so that feature seems to have been passed down through each generation.

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Lifespan and Growth

Drawing of several prehistoric sea turtles.
Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon is believed to have had a long lifespan, possibly living up to 100 years! Like modern sea turtles, it likely grew slowly over time, so only the oldest turtles would be absolutely huge. This long life helped Archelon thrive in the Cretaceous seas for millions of years.

Reproduction and Nesting

Archelon and other prehistoric sea life.
Archelon and other prehistoric sea life. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Although there is little direct evidence, it’s believed that female Archelons likely laid eggs on beaches, just like modern sea turtles. So, they would have traveled to land to lay their eggs in sandy nests just like you’d expect. Hatchlings would then have made the dangerous journey back to the sea just like their modern relatives. Can you imagine the size of those eggs?

Predators of Archelon

Archelon eating squid.
Archelon eating squid. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Despite its size, Archelon still faced threats from predators. For example, large marine reptiles like mosasaurs were likely a danger to both young and adult turtles. However, Archelon’s large size and tough shell provided some defense against these ancient predators.

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Extinction of Archelon

Archelon and some smaller dinosaurs.
Archelon and some smaller dinosaurs. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon became extinct around 66 million years ago, likely due to environmental changes. Specifically, the mass extinction event that wiped out the dinosaurs also affected many marine species. So as the oceans changed, Archelon’s habitat may have disappeared.

Significance of Archelon in Paleontology

Prehistoric turtles swimming together.
Prehistoric turtles swimming together. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon’s fossils have been important in understanding the diversity of prehistoric sea life. For example, its size and unique features provide insight into the evolution of turtles. Today, paleontologists continue to study Archelon to learn more about life in the Cretaceous period.

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Conclusion

Artistic imagining of archelon on the beach.
Artistic imagining of archelon on the beach. Screenshot from Archelon: The Largest Turtle Ever To Have Lived Source: YouTube Channel: Earth 2.0
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Archelon was a remarkable prehistoric creature that roamed the seas millions of years ago. Still today, its massive size, flexible shell, and ancient habitat make it a fascinating subject for study. Even though it has long been extinct, Archelon continues to capture our imagination. Had you ever heard of this prehistoric turtle before?

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