'Pocket' sharks are world's rarest find

Ever heard of a five-inch-long shark? That's a very rare species discovered recently -- and if you ever spotted one, you'd only be the third person to ever do so.

The common name of this species is the "pocket shark", though its scientific name is Mollisquama sp, said a new study.

While it is small enough to fit in your pocket, it's dubbed "pocket" because of the distinctive orifice behind its pectoral fin -- one of many physiological features scientists hope to better understand.

"The pocket shark we found was only five-and-half inches long, and was a recently born male," said lead author Mark Grace from the Southeast Fisheries Science Center (NOAA), Mississippi.

Grace noted that the shark had an unhealed umbilical scar.

"Discovering him has us thinking about where mom and dad may be, and how they got to the Gulf. The only other known specimen was found very far away, off Peru, 36 years ago," Grace said.

Interestingly, the specimen Grace discovered wasn't found in the ocean, but in the holdings of NOAA's lab in Pascagoula.

It was collected in the deep sea about 190 miles offshore Louisiana during a 2010 mission by the NOAA Ship Pisces to study sperm whale feeding.

The dead specimen spent more than three years in a giant freezer waiting to be identified. It turned out to be only the second of its species ever seen.

Grace, who was part of that mission after the rare shark was collected, uncovered the sample at the lab years later.

Partners at the Smithsonian Natural Museum of Natural History in Washington and American Natural History Museum in New York City have also contributed to the study of this shark.

"This record of such an unusual and extremely rare fish is exciting, but its also an important reminder that we still have much to learn about the species that inhabit our oceans," Grace added.

The findings were published in the international journal of taxonomy Zootaxa.