The body of a 150 million-year-old sea monster is hidden under a British cliff, says a scientist. Time is running out to find it.

• The body of a 150 million-year-old pliosaur is hiding under a British cliff.
• Experts have already uncovered the sea monster's seven-foot skull, complete with 130 teeth.

The body of an enormous 150-million-year-old sea monster could be hidden under British cliffs, and time is running out to uncover it.

The seven-foot-long head of the pliosaur, which has been described as an "underwater T. Rex", has already been discovered, complete with 130 razor-sharp teeth.

Now the paleontologist who found the skull hopes that the rest of the beast's body could be nestled in the cliff where the skull was found. It is estimated to be up to 39 feet long.

The coastline is rapidly retreating in this area, up to a foot a year, and this could threaten the specimen's integrity if it starts falling from its 50-foot-high resting place.

"I stake my life the rest of the animal is there," palaeontologist Steve Etches who found the skull, told BBC News.

Etches first uncovered the fossil after his friend and fellow fossil enthusiast, Phil Jacobs, found the skull's snout on a beach in Dorset in the UK. Drone footage revealed the rest of the fossil was peaking out of the cliff above, almost 50 feet in the air.

After a few months of excavation, Etches recovered the skull from the cliff. He identified the dinosaur as a pliosaur, a 30 to 39-foot-long predator with four fins that would allow it to move quickly in the water and pounce on passing prey.

"The animal would have been so massive that I think it would have been able to prey effectively on anything that was unfortunate enough to be in its space," Andre Rowe, a palaeobiologist from Bristol University in the UK, told BBC News.

"I have no doubt that this was sort of like an underwater T. Rex," Rowe said.

Etches' specimen is "very likely a new species," Judyth Sassoon, an expert on pliosaurs at the University of Bristol, told New Scientist.

The skull's crest could suggest that this specimen was not fully grown when it died, per Sassoon.

Etches believes there's more to the beast lurking in the rock. Vertebrae pointing out of the back of the skull suggests the rest of the pliosaur's body could still be intact, ready to be uncovered.

Etches' discovery will be the subject of a new BBC documentary presented by David Attenborough due to air on the UK's BBC One on New Year's Day and on PBS on February 14.