Scientists have found a genetically unique population of miniature sharks off the coast of Belize. They described their results in the Journal of Fish Biology. 

The hammerhead shark family is made up of 10 known species, five of which are on the petite side (relatively speaking). One of those miniature sharks is the bonnethead, Sphyrna tiburo, which meanders through the Atlantic and Pacific Oceans feeding on crabs, shrimp, and little fish. Female bonnetheads are a bit larger than the males, maxing out at around four feet long.

Bonnethead populations appear to be pretty healthy at the moment, but like just about everything else in the ocean these days, their future is pretty uncertain. Researchers decided to assess the bonnetheads’ current situation at the smallest possible level—by looking at their DNA. They collected tiny skin samples from 239 live sharks in the waters off the Bahamas, Texas, Panama City (Florida), Tampa Bay, the Florida Keys, North Carolina, and Belize, then analyzed their genetic code to check up on the sharks’ health. 

Demian Chapman measuring a wee shark. Image Credit: © FIU

The bonnetheads’ DNA looked good—but it also looked sort of odd. The samples taken in Belize were startlingly different from the rest of the bunch. 

Paper co-author Kevin Feldheim leads The Field Museum’s Pritzker Laboratory for Molecular Systematics and Evolution. He said he and his colleagues were quite surprised with their results. "We thought we were doing a standard analysis of a shark population," he said in a statement, "and suddenly, whoa, we were looking at a whole new species."

That’s the short version. The long version is that Feldheim and his colleagues have more work to do before they can be certain they’ve got a brand-new bonnethead on their hands 

"There’s no cutoff in DNA that indicates you’ve got a different species," he said. "Determining when you have a new species is a tricky thing. But these sharks are living in a separate environment from their fellow bonnetheads, and they’re likely on their own evolutionary trajectory."

New species or no, the sharks still need attention and protection. Co-author Demian Chapman of Florida International University said: "Now we have to define the range of each of these species individually and assess them independently against where the potential threats are … our finding of a new species in Belize highlights that there could be more undescribed ones out there, each one facing a unique set of threats."