Car-Sized Prehistoric Sea Turtle Found To Be Largest In Europe

The fossilized remains of a car-sized, prehistoric sea turtle have recently been found in the Spanish Pyrenees.

The huge reptile is the largest-known sea turtle to have been found in Europe, its size rivaling that of giant sea turtles that swam in the shallow seas covering much of what is now North America during the Late Cretaceous Period.

(Photo above is of a leatherback sea turtle, the largest living sea turtle, which has a leathery shell similar to that of the newly-discovered species.)

Giant Prehistoric Sea Turtles

70 million years ago, towards the end of the Cretaceous period, much of what is what is now Europe was an island chain surrounded by shallow seas.

North America, too, looked significantly different from its modern-day form, with a shallow sea, known as the Western Interior Seaway, dividing the continent into eastern and western landmasses.

Swimming in the world’s oceans at this time were numerous sea turtle species (the first sea turtles appeared around 110 million years ago; perhaps even earlier). Some of these prehistoric marine reptiles were true giants; Archelon, which reached lengths of 15 ft. / 4.6 m, is the largest sea turtle yet discovered.

Archelon and other giant prehistoric sea turtle species were found in North America; until recently, the largest-known European turtles of this time reached a “mere” 1.5 meters in length.

This all changed with the discovery of the fossilized remains of a car-sized sea turtle in the Spanish Pyrenees. The species, which has been given the name Leviathanochelys aenigmatica (enigmatic giant turtle), had an estimated carapace length of 12.14 ft. / 3.7 meters. It is the largest sea turtle ever to have been found in Europe, and the second-largest sea turtle species ever discovered.

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How Was The New Sea Turtle Discovered?

The fossilized remains of Leviathanochelys aenigmatica were discovered by a hiker walking in the Spanish Pyrenees in 2016. The Conca Dellà Museum was notified and a team assembled to preserve and collect the specimen.

Further excavations at the site resulted in the discovery of more of the carapace and most of the pelvis. Still to be found are a skull, limbs and tail.

Fossils of Leviathanochelys aenigmatica. Images: Castillo-Visa, O., Luján, À.H., Galobart, À. et al., CC BY 4.0, via Wikimedia Commons (cropped / resized by

Although the remains were fragmented, researchers from the Miquel Crusafont Catalan Institute of Paleontology, the Conca Dellà Museum and the Czech University of Masaryk Brno (MU) recognized that the animal was new to science, and described the new species in a research paper. (source)

What’s In A Name?

Leviathanochelys aenigmatica, the scientific name given to the new species, means “enigmatic leviathan / giant turtle”, the name referring to the turtle’s large size and unusual characteristics.

Leviathanochelys aenigmatica Characteristics

Leviathanochelys has an exceptionally large pelvis with a unique extension on the side that may have been connected to muscles to control abdominal contraction. Scientists think that this could have played a role in the respiratory system, helping the giant turtle to maximize its breathing capacity in deeper waters.

Why Were Prehistoric Turtles So Large?

Although a complete Leviathanochelys skeleton has not yet been found, the size of an animal’s pelvis is often a good indicator of overall body size.

Mosasaurus hoffmanni.
A mosasaur eating a sea turtle. Image by Dmitry Bogdanov.

It is hypothesized that turtles evolved large body sizes during the Cretaceous period due to the presence of large predators such as mosasaurs, which could reach over six meters in length. A large, heavily armored turtle would have been considerably harder to capture than a fish or squid.

The largest turtle ever to have lived is Archelon, a genus found in the oceans around North America during the Late Cretaceous. Archelon was over 4 meters in length and weighed around two tons.

L. aenigmatica evolved separately from Archelon. While we don’t know exactly why the European species grew so large, it is probable that it faced similar environmental factors as the giant North American turtles.

How Big Are Today’s Turtles?

Leatherback sea turtle on beach
A female leatherback sea turtle leaving the water to lay her eggs.

The largest living turtle species is the leatherback sea turtle. It usually reaches around 2 meters in length, but a specimen currently held in the National Museum of Cardiff is almost three meters long and weighs over a ton. This particular animal washed up on Harlech Beach on the coast of Wales in 1988 after becoming trapped in fishing lines and drowning. (source)

The leatherback turtle has the widest distribution of all turtle species, ranging as far north as Norway and Alaska, and as far south as South Africa and New Zealand. The species gets its name from its unique shell, which unlike the bony shells of other sea turtles, is flexible and covered with leathery, oily flesh.

The leatherback turtle is the only living relative of a turtle family that stretches back 100 million years. The species’ population is currently in decline due to bycatch, egg harvest, coastal development, and declines in food availability. Individual leatherback sea turtles are thought to live over 100 years.

How Do Leatherback Turtles Benefit From Being Large?

Although it doesn’t reach the same size as prehistoric turtles such as Leviathanochelys aenigmatica, the leatherback sea turtle is still a very large animal in today’s world, its size helping it to survive where other turtle species cannot.

The leatherback, unlike nearly all other reptiles, is able to maintain a body temperature higher than that of the surrounding waters. Its large size, thick layer of insulating fat, and constant movement enable the leatherback turtle to dive deeper, swim faster, and inhabit colder seas than any other sea turtle species.

Leatherbacks are known to dive as deep as 1,280 meters – deeper than all other diving reptiles, and all mammals except for the beaked whale and sperm whale.

Leatherback sea turtles follow their jellyfish prey into deeper water during the daytime, and shallower water at night. (source) Scientists fitted a satellite tag to a leatherback turtle and found that it spent many weeks in waters that were only 0.4°C (32.7°F). (source)

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What Can We Learn From This Discovery?

The discovery of Leviathanochelys aenigmatica in Europe gives us a clearer image of what our oceans looked like millions of years ago.

Researchers previously thought that these marine giants were found only in North America. The discovery of the new species, with its unique pelvic bone, suggests that giant turtles evolved independently from lineages in North America.

The new species also gives us a clearer picture of the evolutionary trends of sea turtles. It backs the idea that extreme sizes are more common before an extinction event, with smaller sizes becoming more common afterward.

Although only a few bone fragments were discovered, scientists have still been able to piece together an idea of the size of Leviathanochelys aenigmatica and where it fitted into the marine ecosystem of prehistoric Europe. This has raised new questions about how giant turtles were able to evolve on both sides of the Atlantic, and additionally hints towards the potential discovery of more of these enormous animals in the future.

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