Scientists Find Rare Hybrid of Two Other Dolphin Species Clymene dolphins. NOAA Southeast Fisheries Science Center The clymene dolphin is a hybrid of two other species, a phenomenon that is rare among mammals, a new study reports. Researchers used genetic samples to determine that spinner and striped dolphins interbred to form a third species, the clymene, also known as the short-snouted spinner dolphin. All three species live in the Atlantic Ocean, with the clymene eventually forming a distinct gene pool, said Howard C. Rosenbaum, a conservation biologist with the Wildlife Conservation Society and one of the researchers involved with the study. "And the gene pool is robust enough that they've survived over time," he said. This is the first known instance of hybridization among marine mammals, added Ana R. Amaral, a researcher at the University of Lisbon and the American Museum of Natural History who is the lead author of the study. This genetic occurrence is more commonly seen in plants, fish and birds. The researchers analyzed nuclear and mitochondrial DNA from skin samples taken from 72 clymene, spinner and striped dolphins. They found that the clymene's mitochondrial DNA, which reveals maternal ancestry, most closely resembled the striped dolphin. And the clymene's nuclear DNA, revealing paternal ancestry, was closely related to the spinner dolphin. The researchers, who discuss their findings in the journal PLoS One, said it was not clear exactly when in history the hybridization occurred. "We know that spinner and striped dolphins originated between one and three million years ago," Dr. Amaral said. So it was sometime after this. There is still a little "backcrossing" going on between species, where occasionally a spinner dolphin might breed with a clymene dolphin, she added. The three species also live harmoniously in the Atlantic Ocean, even cooperating at times. "Sometimes we see mixed groups of clymene and spinner dolphins," Dr. Amaral said. They hunt for prey together.