A new species of ancient balloon-headed dolphin has been identified from a fossil pulled up by fishers in the North Sea (map), a new study says.

The 2.5-million-year-old species was named Hoekman's blunt-snouted dolphin after Albert Hoekman, the Dutch fisher who trawled up a bone from the creature's snout in 2008.

Measuring up to 20 feet (6 meters) long, the newfound dolphin had an extremely short and spoon-shaped snout that supported a large, high, and protruding forehead.

Bulbous Head Helped Dolphin Navigate?

In looks and size, the new species was similar to modern pilot whales—although its head was much more bulbous, said study author Klaas Post, an honorary curator at the Natural History Museum Rotterdam in the Netherlands.

Post and colleague Erwin Kompanje suspect that Hoekman's blunt-snouted dolphin may have been a direct ancestor or at least a very close relative of today's pilot whales. (See whale pictures.)

As with today's pilot whales, the team also suspects that the new dolphin used its large forehead for echolocation, a biological form of sonar that allows dolphins and some whales to navigate in murky conditions.

"Pilot whales seem to have developed this tool in some special way," Post said via email, "and [Hoekman's blunt-snouted dolphins] seem to have been the forerunner."