Discover The Ancient Sea Turtle The Size of A Car

Written by Kyle Glatz
Updated: March 17, 2023
© Michael Rosskothen/
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The largest modern sea turtles can grow upwards of 6 feet long. While that’s impressive, the ocean waters once contained another turtle that was even larger, heavier, and potentially deadlier. This ancient sea turtle was roughly the size of a car, and the species survived for millions of years in the world’s oceans.

Discover the largest sea turtle to have ever lived in the world and learn where they lived, where their fossils have been found, and more!

What Was the Car-Sized Ancient Sea Turtle?

Archelon turtle's head
The Archelon turtle had a pointy head and a hooked beak.


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The massive, car-sized ancient sea turtle was Archelon, a genus of one species, Archelon ischyros. This sea turtle looked roughly similar to modern sea turtles except that it was far larger.

Archelon’s size was incredible. They measured about 11.5 to 15 feet long based on the recovered specimens. The head protruding from the shell was about 2 to 3 feet long! The turtle weighed somewhere between 4,800 pounds to 7,000 pounds. That’s more than the average weight of a car and almost the same length as the average car. Archelon was a seriously large creature.

The creature’s morphology was interesting too. This reptile had a leathery carapace rather than a keratinous shell like many other turtles. Another interesting thing about this turtle is that it had a long, thin head as well as a very distinct beak. Together with the turtle’s powerful jaws, scientists believe that this animal would eat crustaceans and mollusks in the waters where it lived.

The turtle also had very large, powerful flippers, with a span measuring about 16 feet to 20 feet. Even with these exceptionally powerful flippers, the turtles were not that swift.

When Did the Giant Ancient Sea Turtle Live?

Archelon lived millions of years ago. Scientists believe that the creature first appeared during the Late Cretaceous, about 100 million years ago. The species lived for a long time, too. However, this creature disappeared from the fossil record about 66 million years ago.

The cause of Archelon’s extinction is unknown. However, scientists have many theories about what finally caused them to die out. These include:

  • Habitat loss in the Western Interior Sea
  • An increase in infant mortality and predation
  • A decrease in the water temperature

These are the commonly accepted reasons that the turtle went extinct. Although it died out around the same time that the dinosaurs did, the two extinctions may not be connected at all. Yet, if the turtles survived until the extinction event that wiped out the dinosaurs, then it would have almost certainly spelled the end of the turtles.  

Where Did Archelon Live?

Xiphactinus Fossil in Canada
Turtles were not the only massive creature that lived in the Western Interior Seaway.


Fossil records indicate that Archelon lived in a shallow sea that once covered a significant part of North America. This body of water was called the Western Interior Seaway. The sea stretched from the northwestern portion of what is now Canada, through the middle of the present-day United States, and reached an outlet into the ocean by modern-day Texas and Louisiana.

This sea divided North America into two different landmasses. They were called Appalachia and Laramidia. Appalachia was the landmass to the east, and the Laramidia was the landmass to the west.  The seaway stretched over 2,000 miles.  

This shallow sea was perfect for the Archelon, allowing it to find food and lay its eggs on the beaches near the sea. Within the sea, Archelon probably stayed close to the bottom of the water. That is where it would find the hard-shelled creatures that it preferred to feed upon.  

The former area covered by the Western Interior Seaway provides all the evidence needed to prove that Archelon lived here. After all, fossils of Archelon have been discovered in places like North Dakota, South Dakota, Kansas, and Nebraska.

Where You Can See Archelon Fossils

Largest Sea Turtle - Archelon
Archelon fossils can be found in North Dakota, Austria, and a few other places.


The ancient sea turtle was massive, so its fossils are very impressive. However, they are not widely available to enjoy due to their limited specimens. Still, these fossils can be found in some museums.

One place a person can find Archelon fossils is Naturhistorisches Museum Wien, a museum in Vienna, Austria. Visitors can also find Archelon fossils at the Griggs County Historical Society Museum in Cooperstown, North Dakota. These are two places where people can see fossils of this incredible creature.

What’s the Largest Extant Turtle?

leather-back sea turtle
The leatherback sea turtle is the largest extant turtle.


The largest turtle alive today is the leatherback sea turtle. This creature is very large, weighing up to 2,000 pounds and growing about 6 feet long. That makes it a massive, fascinating creature. However, it does not measure up to the ancient sea turtle, Archelon.

Both turtles have a similar type of outer covering. The leatherback has a leathery carapace just like Archelon had in the past. The leatherback turtles are far more widespread than Archelon ever was, though.

These creatures are said to have a cosmopolitan distribution. That means they live across most of the world. The leatherback sea turtle has been found far to the north like the Arctic Circle and as far south as the southern reaches of New Zealand.

Unfortunately, leatherback turtles suffer from a diminishing population. These creatures are listed as vulnerable on the IUCN red list. Roughly 40,000 nesting females exist in the world today. That number has dropped from over 100,000 in 1980. The future of these creatures could be in jeopardy as they are caught in fishing gear and have their eggs poached for human consumption.

The Archelon was a massive ancient sea turtle that once lived throughout a sea that split North America. It was not the only giant animal that lived during that time, but it was still far larger than any turtle found these days.  

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About the Author

I've been a freelance writer since 2013, and I've written in a variety of niches such as managed service providers, animals, and retail distribution. I graduated from Rowan University in 2014. When I'm not working, I enjoy playing video games, reading, and writing for fun.

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