Leviathanochelys

Leviathanochelys is an extinct genus of giant sea turtle from the Middle Campanian of northern Spain. Although only known from the rear end of the carapace and the connecting pubic bones, these elements clearly show that they belonged to a turtle of great size, comparable in dimensions to the giant Archelon and Protostega from the Western Interior Seaway of the USA. This makes Leviathanochelys the first giant sea turtle known from Europe and one of the largest known turtles of all time. This great size was evolved independently from the American protostegid turtles and was likely an adaptation to the conditions of the Cretaceous oceans covering much of Europe. Being classified in the superfamily Chelonioidea, Leviathanochelys is likely more closely related to modern sea turtles (families Dermochelyidae and Cheloniidae) than the protostegids, which are thought to be more basal and have a more uncertain relationship to modern sea turtles. Leviathanochelys is thought to have been a pelagic animal. The genus contains a single species, Leviathanochelys aenigmatica.

Discovery and naming

The remains of Leviathanochelys were discovered in 2016 by a hiker at the Cal Torrades locality in the Spanish Pyrenees, which corresponds with the lower Perles Formation. Within this locality, the fossil material was discovered approximately 20 cm (7.9 in) above the sandstone that forms the base of the locality, within a layer of grey marls. The turtle was named based on the holotype specimen MCD9884, which represents the posterior end of the animal's shell including the 5th to 8th neural and costal plates, an almost unidentifiable bone thought to be a vertebra and much of the pelvic girdle including both pubis, ischia and ilia.

The name Leviathanochelys is an allusion to the biblical leviathan, a massive marine beast that was chosen due to the turtle's great size.