The identity of a highly decomposed sea creature that recently washed up on a beach in Spain has run the gamut of speculation; everything from an oarfish or a horned sea dragon to the Loch Ness Monster or a shark has been suggested.

The 13-foot-long corpse is so badly decomposed that it bears resemblance to everything and nothing all at once. The mystery creature washed up in Villaricos in Andalusia, Spain, on Aug. 15, according to LiveScience.

Bizarre horn-like protrusions from one end of the creature added to the mystery.

"We have no idea what it could be," Maria Sanchez, a civil protection coordinator, told Spanish newspaper Levante, according to Fox News. "A woman found a piece [of the animal] and we helped her get the rest."

David Shiffman, a shark researcher at the University of Miami, told NBC News that it's hard to tell what the creature is, but that it's plausible that it could be a thresher shark. Thresher sharks have lengthy caudal fins which can be as long as the body of the shark itself.

Shiffman also said the mystery creature resembled a giant oarfish -- the world's longest boney fish, which researchers just recently caught on film for the first time.

But the oarfish idea was later debunked by Dean Grubbs, an ichthyologist at Florida State University, who told NBC that the creature is "definitely a shark skeleton."

"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," he said.

Earlier this year a similar episode of "sea monster" speculation happened when a badly decomposed orca carcass washed ashore in New Zealand.

A video montage of pictures of the creature is below, complete with "X-Files" music.