Researchers have discovered an ancient porpoise with an enormous chin length.
The research team believes the "unprecedented" length of the ancient animal's chin was used to probe the ocean floor, a Yale University news release reported.
The porpoise, dubbed Semirostrum ceruttii, had a jaw extension called a "symphysis," which is essentially equivalent to the human chin.
Most crown porpoises' chins measure only between one or two centimeters (less than an inch) while the Semirostrum ceruttii's was about 85 centimeters long (about 33 inches).
"This is unique anatomy for a mammal," Rachel Racicot, the Yale doctoral candidate who is lead author of a paper about the research, said in the news release. "And it tells us that porpoises once searched for food in a very different way than they do now."
The finding suggests the species was a benthic feeder, meaning it searched for food in the seabed; most of today's porpoises search for food both on the sea floor and in open water.
The 15 fossil specimens, which were all found in California, are believed to have swam the west coast seas between 1.5 and 5.3 million years ago.
The closest-known example of the Semirostrum ceruttii jaw in the modern animal kingdom is found in a bird called the "skimmer" as well as in half-beak fish. Black skimmers use their long appendage to "fly just above the surface of water bodies with their symphysis slightly submerged to probe and scoop small fish and crustaceans," the news release reported. Both of these long-chinned species feed primarily at night, which explains why they would need these "probes."
CT scans of the ancient skulls reveal a series of " extensive nerve canals leading from the symphysis into the rear of the skull." This suggests the animal's symphysis was extremely touch-sensitive and quickly sent information back to the brain.
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