The remains of a mysterious, bizarre “sea creature” found on a Spanish beach has left some experts confounded.

The four-meter-long creature, with what appear to be horns, was found decomposing on Luis Siret Beach in Villaricos, Spain leaving locals wondering if they had caught a glimpse of a mythical sea monster from the deep, Grind TV reports.

“A lady found one and we helped her retrieve the rest,” Maria Sanches of Civil Protection in Cuevas said. “We have no idea what it was. It really stank.”

Experts and residents are struggling to determine what the remains are, with guesses ranging from everything from a relative of the Loch Ness Monster, a dinosaur or sea monster, or an oarfish.

“It’s hard to know what we are dealing with,” PROMAR Sea Life Defence Program spokesman Paco Toledano told Ideal Ameria.

“It’s very decomposed and we cannot identify what it is.”

Mr Toledano said they have sent information about the remains to more other experts, in hopes that they can identify the animal.

It’s not the first mystery remains to lead to speculation of a sea monster. In May, stunned beachgoers on New Zealand’s Pukehina Beach stumbled over the carcass of a mysterious marine animal.

The latest mysterious find is part of a long history of discoveries of mysterious sea creatures. The bizarre, rotting corpses are often mistakenly identified as sea monsters or dinosaurs, or even just mysterious “blobsters”.

In 1896, a 2-metre tall sea creature corpse washed ashore in St Augustine, Florida. Scientists eventually determined it was a new type of giant octopus.

In 2003, the bizarre 12-metre, 13-tonne “Chilean blob” shocked the world when it washed ashore on Los Muermos beach, BBC News reports. Puzzled marine biologists speculated the blob could be a type of giant squid, but DNA tests on the blubbery mass eventually determined it was the remains of a sperm whale.

Marine mammal expert Anton Van Heldon examined the latest “monster” carcass in New Zealand and believes it is a killer whale, based on the fin structure. Killer whales, or orcas, are sometimes spotted in the Bay of Plenty.

This creature from Spain, though? It’s probably just a shark, Florida State University ichthyologist Dean Grubbs told NBC News. Grubbs is a specialist on the biology of fish species – especially sharks.

“That is definitely a shark skeleton,” Grubbs said via e-mail. “The elements toward the back were confusing me, but those are the lower caudal fin supports. The ‘horns’ are the scapulocoracoids which support the pectoral fins.”

The original article appeared on NEWS.COM.AU