A Shark Discovery ‘Didn’t Look Right.’ It Might Have Been a Plastic Toy.

Goblin sharks are deep-sea fish whose frightening, protrusile jaws served as an inspiration for the terrifying creatures in the “Alien” movie franchise. Little is known about these elusive sharks, and sightings of them are extraordinarily rare. They are known to live in deep coastal waters all over the world but have never been found in the Mediterranean Sea.

But recently, a group of scientists reported the discovery of what they said was a goblin shark that had washed ashore on a Greek beach. Their announcement of the find last year in the journal Mediterranean Marine Science has led to a series of events almost as bizarre as the goblin shark itself, involving competing scientific narratives, a retraction and the possibility that maybe all of the fuss was over a children’s plastic toy.

According to the original scientific paper, the Mediterranean goblin shark was discovered by a man named Giannis Papadakis in August 2020. After finding the specimen, the paper said, Mr. Papadakis propped it on some rocks and snapped a photo. The image ended up in the hands of a group of local scientists, and two years later they published it alongside records of other species found in the Mediterranean for the first time.

The paper seemed like a success of citizen science, in which people with no formal scientific training assist professional scientists in research. But it wasn’t long before shark experts around the world started to express their doubts, in a Facebook group, about the authenticity of the goblin shark.

“It didn’t look right,” said David Ebert, author of the book “Sharks of the World.” Dr. Ebert said several things about the shark found in Greece were unusual. “It’s too small, and its gills don’t look like they’re actually open,” he said. “It doesn’t look natural at all.”

Dr. Ebert and others were also skeptical because there had been no direct examination of the shark. The paper was based solely on a photo and a brief description provided by Mr. Papadakis.

In November, a group of shark researchers published a comment paper questioning whether the goblin shark found in Greece was a real animal. “We have doubts,” they wrote, that the goblin shark in the original paper “is a natural specimen.” They argued that the specimen’s lack of teeth, its overly rounded fins and its low number of gill slits were not characteristic of a goblin shark.

Soon after, another image was shared on social media, one that would cause the skepticism to reach a crescendo. It was a plastic goblin shark toy sold by an Italian toy company, DeAgostini, and it had an uncanny resemblance to the goblin shark found in Greece.

DeAgostini, the toymaker, could not be reached for comment.

This toy “shows a great similarity to the specimen in the published image,” said Jürgen Pollerspöck, an independent shark researcher and an author of the paper that presented the doubts about the Greek goblin shark’s authenticity.

Earlier this month, the authors of the original paper doubled down, standing by their original claims in a reply to the concerns raised by Mr. Pollerspöck and his colleagues. They also amended their size estimate from about 30 inches to about seven inches and suggested that the goblin shark in question could be an embryo.

“Embryos of this size are not viable,” Mr. Pollerspöck replied.

Then this week, the authors of the original paper retracted it, as well as their reply to the critique, conceding that there was too much uncertainty about the find. Reached by email, one of the paper’s authors declined to answer additional questions.

So ended a nearly yearlong saga that had many shark sleuths squinting at their computer screens.

Mr. Pollerspöck said it was possible for goblin sharks to be lurking in the depths of the Mediterranean Sea. But he said that none had been found.

Whether the shark in this image is found to be a real fish or just a piece of plastic pollution, critics say that the publication of the image in a scientific journal draws attention to the imperfections of the scientific peer review process.

“In my opinion, the problem and responsibility lies with the editor of the journal and the reviewers,” Mr. Pollerspöck said.

The shark’s unusual appearance wasn’t the only red flag reviewers of the paper should have seen, he said. That the claim in the paper was based on one image provided by a citizen scientist warranted increased scrutiny.

The editor of Mediterranean Marine Science did not respond to a request for comment.

Whether or not the researchers who published the now retracted Greek goblin shark paper ever concede that they published a picture of a toy, Dr. Ebert said he wouldn’t be surprised if something like this happened again, given the problems with peer review and the rates of plastic pollution in the seas.

“Anything’s possible,” he noted.