A restoration of Archelon ischyros
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
clade: Americhelydia
Order: Testudines
Suborder: Cryptodira
Family: Protostegidae
Genus: Archelon
Wieland, 1896
Binomial name
Archelon ischyros
Wieland, 1896

Archelon (from Greek αρχελών meaning ruler turtle) is a genus of extinct sea turtle, the largest that has ever been documented, and the second largest chelonian after Stupendemys.

Discovery and Taxonomy

Research history

The first specimen of Archelon (YPM 3000) was collected from the Pierre Shale of South Dakota by Dr. G.R. Wieland in 1895 and described by him the following year (Wieland, 1896). The largest Archelon fossil, found in the Pierre Shale of South Dakota in the 1970s, measures more than 4 metres (13 feet) long, and about 4.9 metres (16 feet) wide from flipper to flipper. It was a marine turtle, whose closest living relative in the present day is the leatherback sea turtle. Archelon's fossils date to around 75-65 million years ago in the Late Cretaceous period, when a shallow sea covered most of central North America. Most of the known remains have been found in South Dakota and Wyoming. Though anatomically similar to the earlier species Protostega gigas, it was much larger.


The holotype measures 352 cm (11.5 ft) from head to tail, with the head measuring 60 cm (2 ft), the neck 72 cm (2.4 ft), the thoracic vertebrae 135 cm (4.4 ft), the sacrum 15 cm (0.5 ft), and the tail 70 cm (2.3 ft).


Archelon was an obligate carnivore


Archelon inhabited the shallow Western Interior Seaway; the muddy, oxygen-depleted seafloor was probably, on average, no more than 180 meters (600 feet) below the surface, and average water temperature may have been 17°C (63°F) in the Campanian.


Unlike most modern turtles, Archelon did not have a solid shell, but instead had a skeletal framework supporting a leathery or bony carapace. Other distinguishing features include a pointed tail, a narrow skull, a relatively narrow, high-vaulted shell, and a pronounced overbite. The live weight of an Archelon ischyros is estimated at more than 2,200 kilograms (4,900 lbs). They probably had a very strong bite, and were optimized for feeding on pelagic mollusks such as squid. The specimen exhibited by the Museum of Natural History in Vienna is estimated to have lived to be a century old, and may have died while brumating on the ocean floor. However, brumation in reptiles is a response to cold weather and it is unlikely that the Western Interior Sea was ever that cold.

In Popular Culture

  • An Archelon made an appearance in the Hammer Film Productions 1966 remake of One Million Years B.C..
  • Archelon also appeared in the Walking with Dinosaurs spinoff special Chased by Sea Monsters.
  • It appeared in Prehistoric.
  • The film The Land Before Time IV: Journey Through the Mists features a helpful, atypically cave-dwelling Archelon named "Archie" assisting the juvenile sauropod named Littlefoot in the story.
  • An Archelon based Charger appears in Power Rangers Dino Charge as number 21 also known as the Dino gravity charger.
  • It appears in Dino Dan: Trek's Adventure.
  • Archelon can be created in Jurassic Park Builder as a limited edition crustaceavore, even though in reality, it likely ate jellyfish and seedweed like most sea turtles.
  • Archelon made an appearance in the Roblox game called "Dinosaur Simulator."
  • A young Archelon name Leon was a new character that appeared in the 2nd Season of Gigantosaurus (TV series).