Emily Chan
Over the summer, a rare dolphin with thumbs was spotted on two separate occasions by researchers with the Pelagos Cetacean Research Institute as they conducted boat surveys off the coast of Greece.
It was certainly a strange sight to behold, as researchers had never seen such a phenomenon before.
“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,” said Alexandros Frantzis, the scientific coordinator and president of the Pelagos Cetacean Research Institute.
The “thumbed” animal seemed to have no problem keeping up with the rest of the dolphins. It was “swimming, leaping, bow-riding, and playing” right alongside them.
Many types of dolphins live in the Gulf of Corinth, where the unique creature was found. This particular specimen was a striped dolphin. Around 1,300 striped dolphins inhabit the Gulf of Corinth.
The dolphin had unusual hook-shaped thumbs carved into its flippers. Frantzis believes that the irregularity was caused by an expression of extremely rare genes. The fact that the thumbs show up on both flippers proves their existence is not due to illness or injury.
But how and why do dolphins have thumbs? Dolphins belong to a category of marine mammals called cetaceans that have evolved distinct forelimbs with more finger bones than most other mammals.
The bones in a dolphin’s fins are arranged into “hands” resembling those of humans and are encased in a soft-tissue flipper. On human hands, the fingers form a paddle shape in the womb, but the cells between the fingers die off before birth.
“Normally, dolphins develop their fingers within the flipper, and no cells between the fingers die off,” said Lisa Noelle Cooper, an associate professor of mammalian anatomy and neurobiology at Northeast Ohio Medical University.
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