American Oceans

Scientists Discover Dolphin with Thumbs

a dolphin swimming beneath the waves

Dolphins have long intrigued researchers due to their sophisticated communication abilities and complex behaviors. In a striking discovery, marine biologists in Greece observed a striped dolphin with unusual flipper features that resemble thumb-like appendages. These sightings occurred during routine maritime surveys conducted by the Pelagos Cetacean Research Institute in the Gulf of Corinth, a region known for its diverse dolphin population, which includes common, Risso’s, and striped dolphins.

For over three decades, both open-sea research and coastal monitoring of stranded dolphins have been conducted in Greece, yet this anatomical rarity has only recently come to light. This particular striped dolphin, one of around 1,300 in the Gulf, was able to swim adeptly alongside its pod despite its distinctive flippers. Biologists suggest that the altered flipper morphology may be due to rare genes expressed after generations of isolated interbreeding among the dolphin community in these waters.

While this dolphin’s flipper appendages may visually remind us of human thumbs, they lack the opposable function that sets human hands apart. The research indicates that although dolphins have phalanges similar to the bone structure in human hands, the striped dolphin’s flippers were missing some tissues that typically conceal these finger bones. The change most likely occurred during the early developmental stages in the womb, resulting in the hook-shaped protrusions observed.

Despite their appearance, these thumb-like structures are not considered a genetic defect; instead, they could represent an uncommon genetic variation within the dolphin’s population. Their lack of mobility suggests that while they might echo the human thumb in shape, they do not enhance the dolphin’s functional abilities in their marine environment.

In the greater picture of cetacean evolution, all species underwent significant morphological changes to adapt to an aquatic life, resulting in the transformation of ancestral land mammal limbs into the streamlined flippers seen in today’s dolphins, whales, and porpoises. This striped dolphin serves not only as a testament to the genetic diversity among marine mammals but also as an example of the constant surprises nature holds for diligent observers like the scientists at the Pelagos Cetacean Research Institute.

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