Dinosaurs suffered painful arthritis in their huge joints, scientists revealed for the first time today.
Researchers found signs of a degenerative condition similar to human arthritis in the jaw of a pliosaur - an ancient sea reptile that lived 150 million years ago.
The discovery marks the first time arthritis-like diseases have been found in fossilised Jurassic reptiles.
A team from Bristol University examined a giant specimen of the pliosaur Pliosaurus dating from the Upper Jurassic period, which was found in Westbury, Wiltshire.
The eight metre long creature had a large crocodile-like head, a short neck, whale-like body and four powerful flippers to propel it through water.
It has huge jaws and teeth 20cm long - capable of ripping most other reptiles or dinosaurs to pieces - but suffered from an arthritis-like disease, they found.
This caused its left jaw joint to erode, displacing its lower jaw to one side.
The dinosaur is believed to have suffered with the condition for years as there are marks on the bone of the lower jaw where the teeth from the upper jaw impacted during feeding.
Dr Judyth Sassoon, of the University of Bristol, who studied the skeleton, said: "In the same way that aging humans develop arthritic hips, this old lady developed an arthritic jaw, and survived with her disability for some time.
"But an unhealed fracture on the jaw indicates that at some time the jaw weakened and eventually broke.
"With a broken jaw, the pliosaur would not have been able to feed and that final accident probably led to her demise."
There are several signs to suggest the skeleton was of an old female, who developed the condition as part of the ageing process - like many humans.
The pliosaurs large size and fused skull bones suggest maturity, while it is believed to be female because its skull crest is quite low.
Pliosaurs are thought to have been pursuit or ambush predators, feeding on fish, squid and other marine reptiles but would also have been able to scavenge.
They were at the top of their food chains so would only have had to fend off attacks from other pliosaurs.
Professor Mike Benton, a collaborator on the project, added: "You can see these kinds of deformities in living animals, such as crocodiles or sperm whales and these animals can survive for years as long as they are still able to feed.
"But it must be painful. Remember that the fictional whale, Moby Dick from Herman Melville's novel, was supposed to have had a crooked jaw!"
The research was published today in the leading international palaeontological journal, Palaeontology.