No, someone didn't Photoshop thumbs onto a dolphin.

Photos of a very special dolphin inhabiting the waters of Corinth, Greece are surfacing. A dolphin born with hook-shaped "thumb" flippers, was spotted twice this summer by researchers with the Pelagos Cetacean Research Insitute.

The "thumbed" dolphin had no problem keeping up with the rest of its pod and was seen "swimming, leaping, bow-riding, playing" with other dolphins, Alexandros Frantzis, the scientific coordinator and president of the Pelagos Cetacean Research Institute told LiveScience.

“It was the very first time we saw this surprising flipper morphology in 30 years of surveys in the open sea and also in studies while monitoring all the stranded dolphins along the coasts of Greece for 30 years,” Frantzis said.

Scientists don’t believe the dolphins thumbs are caused by illness.

"The fact that this irregularity is found in both flippers of the dolphin and no injuries or skin lesions are present explains why this could not be an illness, but an expression of very rare genes," Frantzis told USA TODAY on Wednesday.

Why some dolphins have 'thumbs'

Dolphins are cetaceans, a group of marine mammals that have evolved distinct forelimbs. The bones in a dolphin's fins are arranged into human-like "hands" encased in a soft-tissue flipper, Bruna Farina, a doctoral student specializing in paleobiology and macroevolution at the University of Fribourg in Switzerland, told LiveScience.

On a human hand, "fingers" form into a paddle-shape, but cells die off between the fingers before birth.

"Normally, dolphins develop their fingers within the flipper and no cells between the fingers die off," added Lisa Noelle Cooper, an associate professor of mammalian anatomy and neurobiology at the Northeast Ohio Medical University.

To simplify, dolphins have thumbs, they're just concealed by flippers. The unique dolphin found in the Gulf of Corinth is missing some of those fingers and the tissue that would encase them.

"It looks to me like the cells that normally would have formed the equivalent of our index and middle fingers died off in a strange event when the flipper was forming while the calf was still in the womb," Cooper said.

It is the thumb and fourth "finger" that remain, resembling a hook.

Mixed-species society of dolphins under study since 1995

The Gulf of Corinth is the only place in the world where striped dolphins live in a semi-enclosed gulf, according to research provided by the Pelagos Cetacean Research Institute.

The dolphins, isolated from larger seas or oceans, join common dolphins and Risso's dolphins to form a permanent mixed-species dolphin society. This dolphin society has been under study by the institute since 1995.

To put this pod in perspective, the genetic distance is like if humans lived in a mixed-species society with chimpanzees and gorillas, Frantzis said.

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