A strange marine creature found washed up on the Cumbrian coast has left sea life experts stumped for answers.

Observant freelance cameraman Martin Boardman was out for a Sunday afternoon stroll with his wife Penny and dog Patch along the Arnside beach when he stumbled across a rotting carcass in the sand.

Mr Boardman said: "I was out walking with my wife and dog when we happened across a little cove and we found the creature in the flotsam that had been washed up. At first I thought it was a porpoise and then I got closer and saw it had a beak. It was about two to two-and-a-half feet long and had a leathery skin but no hair and seemed to be the composite parts of a bird. It was badly decomposed but I am sure that it must be a mammal."

The "dark tan" creature also has what appeared to be two flippers and the stump of a tail that Mr Boardman believes may have been chopped off by a propeller Realising he had discovered something unusual, Mr Boardman, 47, rushed to a local shop to buy a disposable camera and took pictures of the mystery creature which he sent to sea life experts.

The photos have reached establishments as prestigious as the Institute of Zoology, in London, and have been viewed by some of the world's leading experts in marine biology. But whether the creature is a penguin, porpoise, seal or squid remains to be seen.

Warren Crutchley, aquarist at the Aquarium of the Lakes, Lakeside, said although "it was impossible to say" categorically what the creature was, he suspected that it was a squid.

Mr Crutchley said: "We showed the pictures to one of the top five experts in the field of strange sea creatures and he said he thought it may be a squid. They can often decompose in stages. The first things to go are often the tentacles and it undergoes discoloration. Also it has a beak which all squids have."

He added: "One of the best ways to find out whether a creatures is a mammal or not is to cut it open on the beach and see if it has a backbone."

But he said it was impossible to say absolutely which species of squid it was or its age without seeing more photographs.

Mr Boardman's own theory is that the carcass could belong to a primeval species, the zeuglodon - a kind of sea serpent.

He said: "It reminded me of a picture of a dinosaur I saw when I was younger - it does look like a prehistoric creature."