[Photo] A scalloped hammerhead shark (Sphyrna lewini). CREDIT: © Save Our Seas Foundation/Peter Verhoog.

Scientists recently confirmed that endangered scalloped hammerhead sharks have a fishy twin — a newfound species, still unnamed, that is distinct, yet very closely resembles the threatened sharks.

The case of mistaken identity indicates that scalloped hammerhead sharks are even more scarce than once thought, according to some researchers.

Since it's very hard to tell the two species apart — only differences in their DNA and number of vertebrae reveal their true identities — it's likely that previous assessments of scalloped hammerhead sharks exaggerated their numbers because the counts likely included the look-alike sharks.

"It's a classic case of long-standing species misidentification that not only casts further uncertainty on the status of the real scalloped hammerhead, but also raises concerns about the population status of this new species," Nova Southeastern University Oceanographic Center professor Mahmood Shivji said in a statement.

Shivji's team at the Florida university first discovered the new hammerhead species in 2005 when examining the DNA of sharks thought to be scalloped hammerheads based on their physical appearance. A research team from the University of South Carolina independently confirmed the existence of the new species in 2006.

Combined genetic assessments from both institutions show that at least 7 percent of the sharks in U.S. waters originally thought to be scalloped hammerheads turned out to be the newly identified species.

Now, researchers have found the unnamed shark, a so-called "cryptic" species, swimming in waters off the coast of Brazil, thousands of miles from where the species was initially discovered. The find indicates the cryptic species is widespread, and may be facing similar pressure as its nearly identical cousin.

Shark populations around the world have declined precipitously in recent decades, with millions of the iconic fish falling victim to the grisly practice of finning.

Shark fins fetch a high price in China, where they are used for shark fin soup.

Shark finning is largely banned in the United States, and many individual states have banned the trade and possession of shark fins. However, evidence from around the world indicates that finning continues to claim millions of shark lives each year.