Archelon

A giant turtle once lived in the sea.

It was the biggest turtle ever found.

Instead of a hard shell, it had soft skin. This skin was thick and leathery.

The turtle had a strong, hooked beak. It used this beak to eat food. It might have eaten slow things from the sea floor. It also swam to find jellyfish. Large flippers helped it move through the water. It was a mighty sea animal.

Archelon was a giant sea turtle from a long time ago.

It lived during the Late Cretaceous period. It is the largest turtle ever found.

One huge turtle named "Brigitta" was about 4.6 meters long. It could weigh as much as 2,270 kilograms.

Most turtles have hard shells. Archelon was different. It had a leathery carapace, which is the top part of a shell.

This shell was made of thick skin. It may have had small ridges on top. The turtle had a very long head and a hooked beak. It used this beak to eat. It likely ate hard things like mollusks or jellyfish.

Archelon had large, strong flippers. These helped it swim in the deep ocean. It lived in a sea with many other big animals. It might have died out when the sea grew smaller. A cooling climate may have also caused its end.

Archelon was a giant sea turtle from a long time ago.

It lived during the Late Cretaceous period in a place called the Western Interior Seaway. This was a mild to cool area of the ocean. Archelon is the largest turtle ever found in the fossil record.

One huge specimen named "Brigitta" was found in South Dakota. This turtle was about 4.6 meters long from head to tail. It could weigh as much as 2,270 kilograms. It is a very special animal to study.

This turtle had a very different body than most turtles today. Most turtles have a hard shell, but Archelon had a leathery carapace. The carapace is the top part of the shell.

This shell was made of thick, strong skin. It might have had seven small ridges along the middle. Its bones were also quite unique. Some parts of its bone were dense and heavy to act like ballast. This helped the turtle stay steady in the deep, open ocean.

Archelon had a very long head and a hooked beak.

This beak was likely covered in a sheath during its life. It worked much like the beak of a bird of prey. The turtle used its jaws to crush hard things. It probably ate mollusks and hard-shelled crustaceans. It might have also eaten jellyfish or squid while swimming near the surface. Its strong flippers helped it move through the water.

These flippers could spread between 2.4 and 3.1 meters wide.

Scientists first learned about Archelon in the late 1800s.

An American paleontologist named George Reber Wieland found a large skeleton in 1895. He found it near the Cheyenne River in South Dakota. He named the animal Archelon ischyros in 1896. The name comes from Greek words meaning "first turtle" and "mighty." Later, other scientists found more pieces. In 1992, they found the huge "Brigitta" specimen in Oglala Lakota County. These finds help us see how big these animals were.

Learning about Archelon helps us understand how life changes.

For a long time, people thought the leatherback sea turtle was its closest relative. Now, we know that Archelon belonged to a completely separate family called Protostegidae. This family is not related to any living sea turtles. Archelon lived in a sea filled with other big creatures. It shared the water with mosasaurs and plesiosaurs. Eventually, the seaway shrank and the climate cooled. These changes may have caused Archelon to go extinct.

Archelon is an extinct genus of marine turtle from the Late Cretaceous period. It holds the record as the largest turtle ever documented in the fossil record. This massive animal belonged to the extinct family Protostegidae. While it lived in the ocean, it was quite different from the sea turtles we see today. Scientists study Archelon to understand how ancient marine reptiles adapted to life in the open sea.

The anatomy of Archelon was specialized for a life of swimming and feeding. Unlike most turtles with heavy, solid shells, Archelon possessed a leathery carapace. This carapace consisted of bony plates called neuralia and pleuralia. These plates were connected by irregular, finger-like sutures. Because these bony portions were thin, the animal likely had thick, strong skin covering them. This skin provided support for the shoulder girdle. The carapace might have also featured a row of seven ridges along the midline.

Archelon's skeletal structure helped it navigate the deep ocean. It possessed osteosclerotic structures, which are areas of very dense, heavy bone. These acted as ballast to help the turtle stay stable in the water, similar to how whales use weight. Its head was long and narrow, featuring a distinct hooked beak. This beak was likely covered in a sheath, much like the beak of a bird of prey. The jaws were designed for a hammering motion. This allowed the turtle to crush hard-shelled prey like mollusks or crustaceans.

The turtle's movement was powered by massive foreflippers. The humeri, or upper arm bones, were proportionally very large. The radii and ulnae, which make up the forearm, were short and compact. These limbs could spread between 2.4 and 3.1 meters wide. Such large flippers provided the powerful strokes needed for open-ocean travel. They also helped the animal escape from marine predators.

Researchers have identified several important specimens that define this genus. The holotype, catalogued as YPM 3000, was found in 1895 near the Cheyenne River in South Dakota. In 1992, a massive specimen nicknamed "Brigitta" was discovered in Oglala Lakota County, South Dakota.

Brigitta is the largest specimen known to date. It measured approximately 4.6 meters from head to tail. In life, this individual likely weighed about 2,270 kilograms. Another partial skeleton was discovered in 2002 in North Dakota.

The history of Archelon's classification has changed as more fossils were found. American paleontologist George Reber Wieland named the genus in 1896. He based his description on the South Dakota skeleton. Originally, the genus included species like A. marshii and A. copei. However, modern science has reassigned these to other genera, such as Protostega and Kansastega.

Scientists once believed the leatherback sea turtle was the closest living relative of Archelon. We now know that the family Protostegidae is a completely separate lineage from any living sea turtle.

Archelon lived in the northern Western Interior Seaway. This was a mild to cool temperate environment. The waters were filled with other large animals, including mosasaurs and plesiosaurs. Eventually, Archelon went extinct. Several factors may have caused this disappearance. The seaway began to shrink, and the global climate became rapidly cooler. Additionally, higher rates of predation on eggs and hatchlings on land, along with infant mortality in the sea, likely contributed to their end.