A newly-discovered species of ancient turtle is thought to be the largest marine turtle ever discovered in Europe.
Named Leviathanochelys aenigmatica and measuring 3.74 metres in length, it is also one of the largest ever to have roamed the seas, scientists say.
Fossilised remains of the turtle were discovered in the Cal Torrades locality in north-eastern Spain.
The Leviathanochelys also seems to represent a new taxon, or group, of ancient marine turtles, the study published in the journal Scientific Reports said.
No known European marine turtle — extinct or living — has exceeded 1.5m in shell-length, the researchers said.
The largest ever known sea turtle is the Archelon, which lived in the seas surrounding the North American continent between 66 and 100 million years ago.
The Archelon was 4.6 metres long and weighed up to 3.2 tonnes.
The Leviathanochelys remains, excavated between 2016 and 2021, were analysed by a team of scientists led by Angel Lujan from the Autonomous University of Barcelona.
They found a fragmented but almost complete pelvis and parts of the upper shell, which date to the Campanian Age — between 83.6 and 72.1 million years ago.
One key feature they identified was a distinctive bone that protrudes forwards from the front of the pelvis — something not seen in other marine turtles.
Researchers believe the protrusion may have been related to the reptile’s respiratory system.
Based on the size of the pelvis, the scientists calculated that the Leviathanochelys could have reached a body length of up to 3.74 metres.
They estimate the maximum width of Leviathanochelys’ pelvis was 88.9cm, making it slightly larger than the biggest estimate for Archelon’s best-known specimen of 81cm.
The findings indicate that gigantism in marine turtles developed independently in different lineages in both North America and Europe, the researchers said.