"As a whole we know very little about these animals - how old they get, how fast they grow, where their nurseries are," Carlson told Live Science. Scientists haven't done a lot of deepwater surveys, so they don't know if the sharks are really rare, or just haven't been seen, he added.
The Key West shark was slightly smaller than the first one seen in the Gulf, which at 18 feet (5.5 m) long was the largest ever recorded, Carlson said. By contrast, most of the goblin sharks seen off Japan are only about 7 or 8 feet (2.1 to 2.4 m) in length. Also, the new animal is most likely female, because it lacked male sexual appendages known as claspers, Carlson said.
The first and only other goblin shark sighting in the Gulf was in 2000, when one got caught in a ghost crab net off the coast of Louisiana, Carlson said. And the only other sighting in the western North Atlantic Ocean was near a seamount east of Bermuda in the 1970s, he said.
They are usually found between water depths of 1,000 and 3,000 feet (300 and 900 m), where the animals probably feed on small fish and squid, spearing them with their sharp teeth, Carlson said.