A saltwater crocodile found in the Northern Territory has been described as a "freak of nature".

The half-metre long reptile has sharp spurs protruding from the underside of its back legs.

The five millimetre-long spurs connect to a bone stemming from the crocodile's ankle joint.

"I don't know whether a croc's been playing up with a platypus or not, but it looks a bit funny, I reckon," said crocodile hunter and taxidermist Mick Pittman.

"I've never seen anything like it."

Mr Pittman, known as "Crocodile Mick", says he and his family have been in the crocodile industry for 53 years.

He thinks the spurs might be mutant toes.

"I reckon the way it was sitting on his leg, it would have to hinder his existence," he said.

"He would have to be scratching himself all the time when he was walking.

"You can't see any real use for it.

"It's just a freak of nature."

Mr Pittman says he plans to make the crocodile "immortal".

"He's going to have his gut filled up with sawdust and he's going to sit on a mantelpiece somewhere as a freak.

"So I'll make him look as best as I possibly can."

Dr Grahame Webb from Crocodylus Park in Darwin says the spurs are extremely rare.

"I've seen it once or twice in looking at tens of thousands of hatchlings," he said.