A huge, strange-looking fish washed up on a southern California beach recently.

The 2.1m-long fish, identified as a hoodwinker sunfish by researchers from California, Australia and New Zealand, was found on the beach within the Coal Oil Point Reserve (COPR) on Feb 19.

This was the first time the species, which is so rare that it was just discovered in 2017, has been seen in the Northern Hemisphere.

An intern who came across the fish first thought it was an ocean sunfish, which is found in the channel near the reserve. She then posted the pictures of her find on COPR's Facebook page.

An associate professor at University of California Santa Barbara's ecology, evolution and marine biology department, Professor Thomas Turner, hurried down to the beach when he saw the photos online. He then posted some images of his own on an online community website for scientists. He told CNN: "It's the most unusual fish you've ever seen. It has no tail. All of its teeth are fused, so it doesn't have any teeth. It's just got this big round opening for a mouth."

Experts on the other side of the globe then weighed in to identify the fish. Mr Ralph Foster, a fish scientist and the fish curator at the South Australian Museum, and Dr Marianne Nyegaard, the marine scientist who discovered the hoodwinker sunfish species, both felt that it was a hoodwinker sunfish rather than an ocean sunfish.

Where a fish normally has a tail, the hoodwinker has only a clavus - a structure that looks like a rudder, said Dr Nyegaard, who works in the marine division at the Auckland War Memorial Museum in New Zealand. All sunfish have a clavus but the hoodwinker's has a shape that is distinctive, she added.

She was very excited about the discovery. "When the clear pictures came through, I thought there was no doubt. This is totally a hoodwinker," Dr Nyegaard told CNN. "I couldn't believe it. I nearly fell out of my chair."

Samples of the fish were saved for future research, said the reserve.

In reply to one comment on its Facebook page, COPR explained the significance of the find.

"If the fish had died in open ocean, we would have never learnt about its northern distribution, hundreds of parasites, age, size, DNA, etc," it said.

Hoodwinker sunfish have been previously sighted in Australia, New Zealand, South Africa and Chile.