An Ultimate Guide to Archelon: The Ancient Turtle

Leave a comment / / Updated on: 23rd September 2023

Name Meaning“First / Early Turtle”Height4 meters (13.120 feet)
PronunciationAR-che-lonLength3.35-4.57 meters (11-15 feet)
EraMesozoicLate CretaceousWeight1-2.5 short tons (2,000-5,000 lbs)
ClassificationReptilia, Testudines & ProtostegidaeLocationPierre Shale in South Dakota

Archelon Pictures

Archelon | Warpaintcobra via iStock

The Archelon

Gage Beasley Prehistoric's Archelon Concept
Gage Beasley Prehistoric’s Archelon Concept

During the Cretaceous period, fascinating creatures like dinosaurs were known to dominate the earth on the terrestrial level.

The aquatic world, however, also had its set of animals that ruled it, and a notable example is the Archelon.

The Archelon is an extinct turtle that was a major member of the ocean about 80 to 74 million years ago and is still regarded as the largest marine turtle to have ever been documented.

The Archelon is believed to be the ancestor of leatherbacks due to their similarity in structure and shell design.

Leatherback Turtle spawning in the coastline
Leatherback Turtle spawning in the coastline | Michel VIARD via iStock

The bones of the first Archelon fossil recorded in history were discovered in the Pierre Shale of South Dakota by paleontologist George Reber Wieland in 1895.

The paleontologist found the fossils along the Cheyenne River, and during his analysis, he discovered that the skull was missing.

In 1902, a completely different specimen was also found in the Cheyenne River.

Another turned up in Oglala Lakota County, South Dakota, in 1992, and that was declared to be the largest Archelon fossil to be discovered.

In 2002, another Archelon fossil was found in the Pierre Shale of North Dakota.

"Brigitta," the largest specimen, at the Natural History Museum Vienna
“Brigitta,” the largest specimen, at the Natural History Museum Vienna | FunkMonk via Wikipedia CC BY 2.0

After the analysis of the different fossils discovered by paleontologists, the turtle was observed to have a hooked beak and mouth, perfect for devouring large mollusks and smaller crustaceans.

Furthermore, most of the fossils were estimated to have lived for over 100 years, and this is the number of years that paleontologists believe to be the species’ average lifespan.

This extinct sea creature had no identified resting pattern and was probably one of the best scavengers of the period.

This article focuses on the features of the Archelon and the many essential details that facilitated its existence during the Late Cretaceous period.

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

Physical Characteristics

It is important to understand that there are certain features that the Archelon possessed to be recognized among the creatures that ruled the aquatic world during the Late Cretaceous period.

Gage Beasley Prehistoric’s Archelon Size Chart Comparison

Here are some of such features:

Huge Structure

The Archelon is regarded as the largest turtle species ever to be discovered.

Researchers concluded that an average Archelon weighed between 2000 to 5000 pounds, and the length from the head to the tail was determined to be between 11 to 15 feet.

The Archelon had a unique shell structure with 1-2 inch ridges and was covered by a leathery carapace.

The massive size of the Archelon gave it a fighting chance when competing for resources and protecting itself from predators.

Archelon with its massive shell
Archelon with its massive shell | MR1805 via iStock


The Archelon had a strong flipper structure on each side, which it used to swim and probably glide across long distances in the ocean.

The front flippers were likely powerful enough to move the turtle’s entire weight through the water at high speeds.

Eye Vision

The Archelon likely had a remarkable vision that enabled it to navigate the ocean while watching out for prey and predators.

Based on the fossils recovered, the eye structure is placed at the far sides of the head, giving it a wide range of vision.

Large Lungs

The Archelon likely did not dive deep into the ocean often, but even when it did, it probably used its large lungs to hold its breath for a long time.

Other adaptation features include its streamlined, lightweight shell, which probably made it swim faster, and its beak-like mouth for feeding.

Habitat and Distribution

Computer-generated 3D illustration with the extinct giant sea turtle Archelon
Computer-generated 3D illustration with the extinct giant sea turtle Archelon | MR1805 via iStock

The Archelon thrived during the Late Cretaceous period and was well spread around (but not limited to) the shallow areas of the Western Interior Seaway in North America.

It was also deduced that the Archelon preferred shallow areas with muddy/sandy surfaces where it could easily breathe fresh air.

Behavior and Diet

Unlike many marine creatures in the Cretaceous period, the Archelon was possibly solitary, except during the breeding season, when the species gathered in sets.

Their front flippers made it easy for them to swim and likely cover long distances in search of food and significant breeding areas.

During winter, Archelon would have migrated to a warmer region and would ultimately return in the summer to where they once stayed.

This seasonal migration was necessary for breeding, a feature also found in modern turtles.

Archelon migrating in order to breed
Archelon migrating in order to breed | MR1805 via iStock

The Archelon also migrated to keep track of the movement of its prey and was a predatory creature that survived on eating different prey such as mollusks, fish, and small crustaceans.

This ancient turtle possessed structures that enabled it to detect, catch and subdue its prey, with one being its excellent eye vision to identify and track its target.

It might also interest you to know that the Archelon was likely among the greatest scavengers of that era; it was probably always on the lookout for the dead animals that found their way to the ocean’s surface.

Life Cycle

One of the many great characteristics of the Archelon is its very long lifespan.

The female Archelon exhibited an oviparous mode of reproduction; during the breeding season, the turtle probably moved to the shore to lay its eggs in a hole in the sand.

Afterward, it returned to the ocean.

Mid-size baby Archelon
Mid-size baby Archelon | CoreyFord via iStock

Once the little Archelon is hatched, it would likely find its way into the sea by itself and begin living alone for an average of 100 years.

Archelon are believed to first live in the open sea when they were small and could catch prey very fast.

However, the bigger they got, the more they preferred the shallow area of the ocean.

Evolution and History

The Archelon is a creature from the biological class Reptilia, the order Testudines, and the family Protostegidae.

Given the time when the Archelon reigned during the Late Cretaceous period, researchers hypothesized that it is a descendant of captorhinids, basically anapsids that existed during the Early Carboniferous period, about 340 million years ago.

Archelon reigning during the Late Cretaceous period
Archelon reigning during the Late Cretaceous period | MR1805 via iStock

The captorhinids later went extinct almost at the end of the Triassic period about 250 million years ago, and the Archelon became extinct towards the end of the Cretaceous period.

Still, scientists have reasons to believe that the creature has evolved into the modern turtle we can identify now as leatherback.

This is likely a result of their familiarity with the properties of their shell.

Interactions with Other Species

The Archelon, just like we noted earlier, was likely a solitary creature.

Still, this does not rule out the possibility of interacting with other animals during the Late Cretaceous period.

It is safe to say that the Archelon interacted with other ocean animals in that period due to competition for resources, with a notable example being plesiosaurs.

Archelon interaction with other ocean creatures in the past
Archelon interaction with other ocean creatures in the past | MR1805 via iStock

The Archelon is also believed to have interacted with other turtles in different food and nesting sites.

Male Archelon interacted with the female species to reproduce more of their kind.

While we can only infer the Archelon’s interactions with other species, we can be sure that the creature played a significant role in the ecosystem during that period.

Cultural Significance

Since the discovery of the Archelon in the 19th century by Wieland, the study of the fossils has helped increase the knowledge of paleontologists on the evolution of sea turtles and the research of other prehistoric sea animals from the Late Cretaceous period.

The discovery of this creature’s fossils has helped the researchers understand the turtle’s biology.

Replica of a 75 million year old "Archelon ischyros" from South Dakota
Replica of a 75 million year old “Archelon ischyros” from South Dakota | Mike Beauregard via Wikipedia CC BY 2.0

The fossils of the Archelon have been used over time for many reasons, one being the reconstruction of the Late Cretaceous marine ecosystem to have a deeper understanding of the evolution of sea animals of that time.

The fossils are also used for tourist attractions to help inform and educate people about the creature’s existence.

For example, the first fossil discovered has been on show at the Peabody Museum of Natural History, Yale University in Connecticut City, as far back as 1907.


The Archelon genus of the family Protostegidae is the largest turtle ever documented in history.

This remarkable creature is, by most standards, regarded as one of the prehistoric animals that ruled the marine world during the Late Cretaceous period about 80-74 million years ago.

The first fossils of Archelon were discovered in the 19th century by paleontologist George Reber Wieland, and this scientific study helped paleontologists understand the creature’s biology.

The Archelon was a giant turtle that thrived in the marine world for many reasons, some of which are the adaptive structures discussed in this article.

The Archelon exhibits an oviparous mode of reproduction and has a long lifespan, just like modern turtles.

Researchers concluded that the Archelon resided mainly in the warm and shallow areas of the ocean.

The Archelon might be prey to stronger animals like sharks, but there’s no denying that this creature was an exceptional hunter with unique features that helped it catch its game.

In all, the Archelon is a fantastic creature that, when studied, can be an avenue to broaden our knowledge of a lot of prehistoric marine animals in the Cretaceous Era.


How Did Archelon Protect Itself From Its Predators?

Because of its big structure, the Archelon was most likely prey only to a few animals like sharks and the mosasaur.

While it remains unclear whether the Archelon possessed a protective system to help defend itself from its predators, it probably rarely came in contact with them, as it rarely dived into the deep ocean.

What Makes Archelon Different From Other Turtles?

Apart from its distinctive size, the Archelon had a different rib structure from other sea turtles where the first rib does not meet the first pleural.

Can Archelon Survive on Land?

The Archelon is undoubtedly an aquatic creature, but it is known to have also survived on land.

However, it is important to note that the Archelon is more likely to be at a speed disadvantage when on land than when it is in water.

Also, after a baby Archelon has hatched on land, it cannot spend long before going back into the water, as it is dependent on the aquatic environment for survival.

What Are the Descendants of the Archelon as of Today?

The Archelon has been known to be extinct as far back as the end of the Cretaceous period, and therefore we cannot say for a fact that the Archelon has evolved into any modern turtle of today.

However, due to their similarities in structure, a lot of scientists believe that the Archelon is closely related to today’s leatherback.


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