Archelon Ischyros, commonly known as Archelon, was a prehistoric giant sea turtle whose fossilized remnants were discovered in Late Cretaceous strata in North America 100 million to 66 million years ago.
Archelon belongs to the family Protostegidae, a classification that distinguishes it from modern turtles due to its unique skeletal framework and lack of a solid shell. It is frequently imagined to be remarkably similar to the leatherback turtle.
Keep reading to unlock the fascinating history of these ancient giants.
Appearance
The Archelon is an enormous ancient species of sea turtle. It had a leathery, streamlined shell instead of a solid, bony carapace like modern sea turtles. This shell called a carapace, was not solid bone but rather a skeletal framework covered by a layer of skin and fat, which would have made it more flexible.
Archelon’s head could not be fully retracted into its shell, unlike some modern turtles. Its skull was relatively small compared to its body size, with powerful jaws likely used for crushing or shearing food.
The cranium was noticeably long and narrow. It resembled the beaks of raptors because it had a distinct, hooked shape and a sheath covering it.
Its front flippers were long and paddle-like, well-adapted for swimming in the open ocean. The back flippers were shorter and helped with steering.
With a length of up to 4 meters (13.1 feet) and a weight that could exceed 2,200 kg (approximately 4,550 pounds), the skeletal framework supported its massive body and large limbs designed for powerful swimming.
The largest specimen measured over 4 meters (13 feet) in length and about 5 meters (16 feet) wide from flipper to flipper.
Swimming Adaptations
The streamlined shape of Archelon, accentuated by its pointed tail and narrow skull, facilitated efficient swimming and maneuvering in the pursuit of prey, distinguishing it from many sea turtles today.
The shell is neutrally buoyant. This is the point at which the body of a fish and other aquatic organisms adapt to prevent it from floating to the surface or sinking to the bottom.
To overcome this obstacle, the animal’s body alters in ways, including the development of denser, thicker bones that counteract the lifting action of the air in its lungs. This prevents the animal from bobbing around on the surface.
Evolutionary Significance
Archelon’s large size and adaptations, such as star-shaped plates for neutral buoyancy, reveal significant evolutionary strategies. These features not only supported its survival in the diverse marine ecosystems of the late Cretaceous period but also provided insights into the evolutionary journey from prehistoric animals to the leatherback sea turtle and other sea turtles today.
Habitat
The largest sea turtle ever discovered, lived in the Western Interior Seaway, an inland sea that split North America into two landmasses during the Late Cretaceous period. This sea stretched from the Gulf of Mexico to the Arctic Ocean, covering much of the midwest United States. Fossils of Archelon have been found in states like the Pierre shale of South Dakota and Wyoming, which were once covered by this ancient sea.
Fossils discovered within the Pierre Shale geological formation, suggest that they thrived in a shallow sea environment.
Strong swings could be generated for cross-ocean migration and, if necessary, escape from other aquatic predators. It lived in the northern Western Interior Seaway, a location with warm to mild temperatures where plesiosaurs prevailed.
The average depth of the muddy, oxygen-depleted habitat that they thrived in was possibly slightly more than 600 ft, and the water’s typical temperature could have been 63 °F.
Diet
Similar to some modern turtles that feed on jellyfish and squid or shrimp. Archelon’s diet also included these soft-bodied cephalopods, indicative of its varied predatory habits. Some of the theories say that it might have preyed on ammonites.
Its jaws were designed for crushing, indicating that the turtle consumed huge crabs, octopus and mollusks as well. Archelon might have been easily sustained by the many thin-shelled, bottom-dwelling Cretaceous shellfish, some of which exceeded 4 ft in diameter.
Reproduction
Archelon only ever ventured onto the shore to lay eggs, just like turtles do presently. On the other hand, these eggs would ultimately hatch, and the young might have had to outrun a horde of predators to reach the ocean.
Except for a few species, all contemporary turtles have a regular behavioral pattern of nest excavation. Most turtles create chambers in which to lay their eggs. The female begins to excavate the chamber with alternate scooping motions of the back legs after she locates the preferred nesting place. It is theorized that this originated from Archelons.
Threats
Because of the presence of natural predators such as mosasaurs, like Allosaurus and perhaps even sharks like Cretoxyrhina, likely, Archelon was still not completely protected from predators, especially from strikes on the flippers. However, the size of their shell alone may have been sufficient to keep certain carnivores.
While Archelon faced threats from formidable predators of its time, including dinosaurs and the gigantic turtle Stupendemys, its size and defensive adaptations provided some level of protection against the harsh realities of the late Cretaceous period.
At the very least, adult males would have been more challenging to catch than other sea reptiles with thinner bodies.
It is thought that Arechlon would use its hardened underside plates as a sort of defense mechanism. This was derived from bite marks found alongside different fossils suggesting that they were prone to blind predator attacks.
4 More Facts About Archelon
- The largest skeleton, which showcases the remarkable size and structure of Archelon, is displayed in Vienna, highlighting its importance both in the USA and internationally.
- Archelon was the largest turtle species to have ever been reported.
- They went extinct about 68-66 million years ago.
- It lived during the same period as the dinosaurs, but it outlived them.
FAQs
Why did the Archelon go extinct?
At the end of the Late Cretaceous epoch, the Archelon is thought to have gone extinct. This indicates that it was extinct after 66 million years. Scientists think that it went extinct as a result of climate change, as altered environmental circumstances have a direct impact on the availability of food.
Did the Archelon have any predators?
Yes, Archelon likely had predators, despite its massive size and the protective features it possessed. Predatory threats to Archelon during the Late Cretaceous period could have included large marine reptiles such as mosasaurs and plesiosaurs, which were apex predators in the marine ecosystems of that time. Additionally, large sharks of the Cretaceous, such as Cretoxyrhina, might have also posed a threat to Archelon, particularly targeting younger or smaller individuals.
How did the Archelon protect itself?
Archelon shells were notably strong, and they had a large diameter, so it would be essentially impractical for a large predator to bite on the shell or even try to swallow them whole as this would, at the most, scratch the surface of the shell. However, its flippers were made of flesh, making them a target for predators to bite, rendering them immobile.
What does the name Archelon mean?
The name “Archelon” is derived from two ancient Greek words: “Arkhe” (ἀρχή), meaning “ruler” or “first,” and “Chelone” (χελώνη), meaning “turtle.” Thus, the name can be translated to mean “ruler turtle” or “first turtle,” reflecting its status as one of the largest sea turtles known and perhaps its ancient lineage among turtles.
Where are Archelon fossils found?
American paleontologist George Reber Wieland initially discovered the Archelon in 1895. He discovered the species’ first-ever fossil in South Dakota’s Pierre Shale geological structures. He noticed a specimen that had been lacking its cranium. But in 1897, a different individual discovered a petrified turtle skull in the same location.
