A tiny shark found in the Gulf of Mexico nearly 10 years ago has turned out to be a new species.

The American pocket shark - named after the pouches it has near its front fins and not its diminutive size - was collected during a 2010 survey to find out what sperm whales eat.

The five-and-a-half inch male shark has five features not seen in the only other known specimen of this kind - which was captured in the Eastern Pacific Ocean in 1979 and is now housed at the Zoological Museum in St Petersburg, Russia.

Its mysterious pouches squirt little glowing clouds into the ocean, according to scientists who have been studying the creature.

The details of the new species are described in an article in the journal Zootaxa collated by Mark Grace of the NMFS Mississippi Laboratories of the National Oceanic and Atmospheric Administration (NOAA) and Henry Bart and Michael Doosey of the Tulane University Biodiversity Research.


On the discovery, Mr Grace said: "I've been in science about 40 years and I can usually make a pretty good guess about a marine animal's identity.

"I couldn't with this one."

He turned to experts at Tulane University and the American Museum of Natural History in New York, as well as the Florida Museum of Natural History, located at the University of Florida.

A 2015 paper identified the shark as the second of its kind, but it took four more years of studying the creature to be sure it was a new species.

"The fact that only one pocket shark has ever been reported from the Gulf of Mexico, and that it is a new species, underscores how little we know about the Gulf - especially its deeper waters - and how many additional new species from these waters await discovery," Bart said.

Researchers believe the shark uses its pouches to squirt a fluorescent fluid to help conceal it from prey or predators.