This shark is tiny, has only been seen twice – ever – and has two pockets next to its front fins.
That’s why it’s called a pocket shark, and this particular specimen was discovered in a US National Oceanic and Atmospheric Administration (NOAA) freezer in 2013.
NOAA biologist Mark Grace found it after spending more than 30 years working his way through bags of frozen specimens.
“I wasn’t really sure what it was,” Grace told PhysOrg. “That pocket over on the pectoral fin, I had never seen anything like that on a shark.”
Together with Tulane University biologist Michael Doosey, Grace co-authored a study published in the journal Zootaxa in which they eventually identified the shark.
It’s just under 14cm long, although it is just a baby and still has an umbilical scar. The only other specimen seen, a 42cm female, was fished up off the coast of Peru 36 years ago.
From a tissue sample that was collected, the team was able to place the specimen into the genus Mollisquama — the shark family Dalatiidae. That means the pocket shark is related to the kitefin and cookie cutters and therefore likely to be one of those responsible for removing oval plugs of flesh from their bigger prey.
The next mystery for the team studying the shark is what the pockets are for. They cover about 4 per cent of the shark’s body and the only clue so far – from the Russian specimen – is that they may secrete some kind of glowing fluid or pheromone.
“This record of such an unusual and extremely rare fish is exciting,” Grace said in a statement on the NOAA website.
“But it’s also an important reminder that we still have much to learn about the species that inhabit our oceans.”
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