A mysterious creature with a crocodilian head and a dolphin-like body has been photographed in China, prompting thousands to guess its identity.

The unfamiliar animal was reportedly photographed by puzzled fishermen in a river near Zhoushan in east China, with the images circulated on various Mandarin websites, such as People’s Daily Online, BTime and 163.

Online commenters speculated widely. Some argued it was a saltwater crocodile or giant salamander; a deformed fish, whale or shark; or even a completely unknown species. Especially confusing to some were the white growths, presumably teeth, poking out of each side of the creature’s beak.

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The animal looks even weirder with its mouth open.

More informed readers identified it as a beaked whale, an explanation confirmed by experts who spoke to English news websites.

This did little to clear up the mystery, as not much is known about the animal group – and there are many species.

In a previous interview with Fairfax Media, Museum Victoria palaeontologist Dr Erich Fitzgerald described the animals as “particularly enigmatic” and “the most poorly known group of whales”.

Many of the whales are named for their discoverer, such as Andrew’s beaked whale, Baird’s, Longman’s, Sowerby’s, Hubbs’, Blainville’s and so on.

The enigma of their lives is often attributed to the fact they are thought to be some of the deepest-diving of all whales.

If indeed the Chinese specimen is a beaked whale, then the white protrusions on its beak are likely teeth. In many beaked whale species, these are reportedly only visible in males and are used for fighting and to attract females.

The confusion of the Chinese fishermen is to be expected, as beaked whales usually spend their lives in the deep ocean beyond the continental shelves. If the photographed animal was indeed seen in a river, this would be strange.

Rear view of a Blainville’s beaked whale photographed near Portugal. Photo: Luis Dias

An Australian academic at the University of New South Wales reported the identification of a new beaked whale, the Deraniyagala’s, in the Marine Mammal Science journal as late as 2014. In a statement at the time, Dr Merel Dalebout said the whales were rarely seen alive.

“A number of species in this group are known from only a handful of animals, and we are still finding new ones, so the situation with Deraniyagala’s whale is not that unusual,” Dr Dalebout said.

“For example, the ginkgo-toothed beaked whale, first described in 1963, is only known from about 30 strandings and has never been seen alive at sea with any certainty. It’s always incredible to me to realise how little we really do know about life in the oceans. There’s so much out there to discover.”

The New Daily contacted Dr Erich Fitzgerald for comment.