New Sixgill Shark Discovery in Atlantic Ocean May Finally Explain How Species Outlived the Dinosaurs

Along with the nautilus, horseshoe crab, and coelacanath, sharks have some of the oldest-surviving species around. One of the more ancient is the sixgill shark, part of the Hexanchidae family—their species is so old that they existed before the time of the dinosaurs, and still have six gills, rather than the regular five featured in more recent species. Sixgills are known all over the world and usually come in two varieties: the big-eyed sixgill and the bluntnose sixgill. Now, scientists have discovered a new species that has gone undetected for years.

The new sixgill lives primarily in the Atlantic, as opposed to the others, which live in the Indian and Pacific Oceans, respectively.

All sixgills share one thing in common, however: the spend part of their time in deep, deep water (depths of about 6,000 feet for the bluntnose and around 1,900 feet for the bigeyed) and move to shallower waters at night, presumably to hunt.

Despite being known by dozens of different names (including bull shark, cow shark, gray shark, and mud shark), scientists still don't know much about sixgills, including how many there are left in the ocean. The discovery of this new species is especially surprising, since the new sixgill looks similar to its cousins.

"We showed that the sixgills in the Atlantic are actually very different from the ones in the Indian and Pacific Oceans on a molecular level, to the point where it is obvious that they're a different species even though they look very similar to the naked eye," said Toby Daly-Engel, a shark biologist at the Florida Institute of Technology.

This definitely isn't the first time scientists have discovered a new species by looking a bit closer at marine animals: an undergrad in Alaska identified a new species of Giant Pacific Octopus in 2012 just by noticing that some of the octopi fishermen had been hauling in for years looked different from the regular description of a GPO. It just goes to show that there's still a lot to learn about our oceans, especially the creepy, deep-sea parts.