The bizarre creature - which according to experts could be a dolphin, porpoise or just a large fish - was found in Liverpool on Thursday afternoon.

Scientists say it was found “badly decomposed” and probably died a long time ago.

Window cleaner Sean Hall said he was walking with a colleague when he found the mystery animal.

The creature appeared to have fangs, he said, and its skin felt “slimy” to touch.

He said it reminded him of a “river monster - something really pre-historic”.

He told the Liverpool Echo : “At first we thought it was a seal, and then we got closer.

“We thought it was in trouble, so we went over to have a look, to see if we could help it back to the sea. But it was dead.”

He added that the creature didn’t even look like it had eyes.

Sean said: “It was really strange.”

The 28-year-old said he called various animal charities for help identifying the creature, but remained in the dark.

Experts were left mystified by photos of the creature on Friday.

Dr Leonie Robinson, a lecturer in marine biology at the University of Liverpool, said: “Unfortunately it is so rotten that it has lost most of its identifying features.

“It might be easier to identify in the flesh, but based on the images supplied it could be anything from a porpoise to a large fish (grenadier possibly).”

Dr Robinson added that the creature “must have been dead a long time” because its head has “rotted back to its jawbone”.

An RSPCA expert said the creature is “most probably a member of the cetacean family, which includes dolphins and porpoises”.

The Mirror