Remaining in the ground for 165 million years, an ancient marine reptile has been excavated from a quarry in eastern England. The fossils belong to what is suspected to be a new species of plesiosaur, which would have cruised the world’s oceans at a time when the dinosaurs were treading the land.

The almost-complete skeleton measures 5.5 meters (18 feet) long, and as possibly the first of its kind, has been nicknamed “Eve.” When alive, she would have had a round, barrel-like body with four flippers, a short tail, and a 2.5-meter-long (8-foot-long) neck. Although the skeleton is missing its hind flippers and parts of its fore-flippers, palaeontologists still plan on studying the specimen to find out as much as they can about how it lived.

The vertebrae from the 5.5-meter-long (18-foot-long) marine reptile. Oxford University Museum of Natural History

The discovery was made by Dr. Carl Harrington from the Oxford Clay Working Group, who first noticed a small piece of bone sticking out of the clay in 2014. After four days of digging, Dr. Harrington and his team excavated more than 600 bones, and then spent a further 400 hours cleaning and repairing the fossil. “I’d never seen so much bone in one spot in a quarry,” he explained. “As I was digging amongst the wet clay, the snout of a plesiosaur started to appear in front of me. It was one of those absolute ‘wow’ moments – I was the first human to come face to face with this reptile.”

The bones are suspected to be from a completely new species of plesiosaur, but further analysis will need to be carried out to determine this for certain. Despite popular misconceptions, plesiosaurs aren’t actually dinosaurs, but marine reptiles. As the dinosaurs dominated the land, the plesiosaurs, ichthyosaurs, and mosasaurs ruled the seas, with hundreds of species described from almost every ocean.

A selection of the fossils found in the quarry in Cambridgeshire, now to be studied by Oxford palaeontologists. Oxford University Museum of Natural History

While the mosasaurs were apex predators, no doubt hunting the other two down, the plesiosaurs and ichthyosaurs were much more like dolphins in modern seas, chasing and corralling fish, squid and other smaller marine critters. While the streamlined, dolphin-like ichthyosaurs would have been speedy hunters, how exactly the long-necked and slightly ungainly plesiosaurs managed to catch fast-moving fish has been the center of debate ever since they were first discovered almost 200 years ago.

The new find has been donated by building product manufacturer Forterra, who own the site where the fossils were found, to the Oxford University Museum of Natural History, where the final part of the skeleton will be carefully removed from the clay in which it is still encased. So far, researchers have conducted a CT scan of the block in order to determine where the bones are and to aid them when they begin to excavate it. When the fossil is fully cleaned, it will be studied by palaeontologists who will hopefully be able to identify, or even name, the species, and then put it on display and used for education.