150-Million-Year-Old Pliosaur Had Arthritis

20120516-003619.jpgA 150-million-year-old pliosaur jaw has been found to have signs of arthritis. This is the first time a degenerative disease like arthritis has been found in Jurassic reptiles.

Pliosaurs were a type of sea reptile living during the Jurassic period, 150 million years ago. Around 8 meters long, with 2-meter jaws, they looked somewhat like a whale with a crocodile’s head. And with teeth over 20 cm long, they would have had a very damaging bite.

The individual in question had signs of degeneration in its jaw similar to arthritis, which had eroded its left jaw joint, making the jaw displaced to one side. The degeneration apparently didn’t affect its hunting ability much, as there are marks on the lower jaw from where the upper teeth impacted it during eating.

Some signs on the skeleton suggest that it was an old female, and possibly developed the condition as a process from aging.

It has fused skull bones suggesting that it was a mature specimen, and the skull crest is lower than in other specimens, suggesting it would be female.

20120516-003635.jpg Dr Judyth Sassoon, the University of Bristol scientist, who began the research, 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.”

It’s thought that pliosaurs were either pursuit or ambush predators, feeding on fish, squid, and other marine reptiles, while sometimes scavenging. They were at the top of the food chain, so they only had competition from other pliosaurs.

Professor Mike Benton, a collaborator on the project, said: “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 just published in the Palaeontology journal.

Source and Images: University of Bristol

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