The titanic turtle, which is likely to have had a body length of around 12.3 feet (3.7 meters), has been named Leviathanochelys aenigmatica by the paleontologists.
In a statement, the researchers explained that they identified the specie from a complete pelvis fossil and fragments of fossilized shell uncovered between 2016 and 2021 at the Cal Torrades locality in northeastern Spain.
According to livescience, the giant reptile likely cruised around Europe's ancient oceans between 83.6 and 72.1 million years ago.
Its body is twice the size of leatherback turtles, which are the largest living marine turtles who can reach up to 5.9 feet (1.8 m) long.
However, the researcher's statement details that the newly found reptile falls short of the record set by the world's largest-ever turtle, the extinct Archelon ischyros, which had a maximum body length of 15 feet (4.6 m).
Fossils of giant turtles are usually found in North and South America, which means that this is the first European marine turtle, living or extinct, to have ever been discovered.
During the discovery, the scientists found that the ancient reptile's body provides interesting clues about its revolutionary past.
They discovered that the turtle's pelvis bone has an unusual protrusion, potentially linked to the respiratory system, which is unlike anything seen in modern or extinct turtles, according to the statement.
This means that the new information upends anything that researchers have seen before in the evolution of turtles as it suggests that there was more than one specie that grew to such an extreme size.
Despite this, the discovery of the L. aenigmatica is not the only one that has taken place in present times.
In 2021, researchers in Venezuela discovered a giant, nearly intact, shell belonging to a freshwater turtle known as the Stupendemys geographicus.
This species lived around eight million years ago in northern South America and its shell measured at nearly 8 feet (2.4 meters) long, livescience reports.
According to the research, the giant reptile weighed an estimated 2,500 lbs. (1,145 kilograms), which is almost 100 times the size of its closest living relative, the Amazon river turtle, and twice the size of the marine leatherback.
Senior researcher Marcelo Sánchez-Villagra said at the time of the discovery that its impressive shell makes the ancient creature "one of the largest, if not the largest turtle that ever existed."
He also added that it's likely the species achieved its record-breaking size due to the warm wetlands and lakes in its habitat.